Horse Articles

  • Developmental Orthopedic Diseases: Part 1, What are they and why do they occur?

    Written By Dr. Kris Hiney

    Developmental orthopedic diseases are a serious concern for the equine breeder.  All of the hard work and preparation of selecting the right match between mare and stallion, the hours put into proper mare care, culminates hopefully in the arrival of a sound, healthy foal.  All of this excitement and hope can be ruined if your foal ends up having skeletal abnormalities which may jeopardize his future success.  With this article we will explore some of the many causative factors of this spectrum of disorders and what you may be able to do to prevent or reduce the likelihood of their occurrence.

    First of all, developmental orthopedic diseases, or DOD, is actually a generic term for a host of disorders.  Simply put, anything which is an abnormality of the horses’ skeletal system during its formative years can be classified as a DOD. The most commonly occurring maladies are angular limb deformities, flexural limb deformities, osteochondrosis and physitis.

    Angular limb deformities

    Angular limb deformities are very common in all breeds of foals. These can include either an inward deviation of the joints (varus) or outward deviation of the joints (valgus).  Most commonly these deviations are seen in the knee, hock and fetlock joints. The foal can have one or more joints affected, and can also vary quite widely in the severity of the condition.  The causes of this condition vary; with some the manager can address, while others are due to random chance.   Both premature and dismature foals very commonly have angular limb deformities due to the lack of strength in supporting structures, or the failure of complete ossification of the cuboidal bones (small bones of the knee and hock).  The causative factors of these conditions may be an infection or inflammation of the placenta or uterus, twinning, and severe stress in the mare.  Development of angular limb deformities post foaling is due to a difference in the growth rate across the inside and outside of the growth plate.  In essence, the difference in speed in bone development causes the bone to veer to one side or the other.  This can be due to a variety of factors including dietary imbalances or environmental factors, as well as genetics.

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    Premature foals are those born before 320 days of age, while dismature foals may be of a normal gestational age but are weak, small and appear unready to have been born.  These foals are typically thin, are slow to stand, have poor suckle reflex, can chill rapidly and are marked by fine silky hair coats and soft ears and lips.  These foals will require a high level of assistance in their care, but with proper supportive care and a lot of time and effort, can continue on to lead normal lives.

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    If your foal does have angular limb deformities, there are actually many therapeutic management techniques used to help straighten the limb.  They range from quite simple to the complex and expensive, usually depending on the severity of the deviation.  Conservative techniques involve stall rest in order to prevent uneven loading of the foal’s developing legs.  The foal may be bandaged or splinted, or the hoof can be trimmed or glue-on extensions can be used to help straighten the limb.  For example if the foal has a valgus deformity in in its knee (the lower leg will sweep outwards), the outside hoof wall is lowered, or a glue on extension is placed on the inside of the hoof.  Often dramatic improvements are seen with these simple techniques.  If the limb deviation is more severe, and budgets allow, corrective surgery may be required.  These include periosteal stripping, or placing screws, staples or wires across the growth plate.  The goal of periosteal stripping (removing a section of the periosteum, or membrane covering the bone) is to accelerate growth of the side of the bone growing too slowly. Typically this procedure is done in young foals.  Alternatively, transphyseal bridging is used to slow down the rate of growth on the side of the bone with too fast a growth rate.  However, before deciding on which management technique is the correct one for your foal, be sure to consult with your veterinarian.  Mismanagement can acerbate the problem, and it is also possible to overcorrect the foal, and end up with a deviation in the opposite direction!

    Flexural limb deformities

    Flexural limb deformities are more commonly referred to as contracted Glue on shoe extension can correct contracted tendonstendons.  Foals can either be born with flexural limb deformities, or they may develop later in life.  Foals born with flexural limb deformities may be due to poor positioning in the uterus, toxicities, genetics or infections in utero.  If the condition is mild, foals can recover typically with just restricted exercise.  Foals should be allowed some exercise either in a paddock or by hand walking for short periods of time.  Additionally, the veterinarian may choose to use oxytetracycline to help relax tendons in more severely affected foals.  Some foals may require splints or casts to help in straightening the limb.  However, this should only be done with a veterinarian’s  supervision as  it is quite easy for the foal to develop pressure sores and may be painful.  Acquired flexural limb deformities can be due to traumatic injuries which cause the foal to protect the limb and not bear full weight on it.  The reduced stretching of the tendons with normal loading results in tendon contracture.  They can also be due to a discrepancy in the growth rate between the flexural tendons and the long bones.  It can also be completely normal to see young horses having temporary periods of being over at the knees.  If the foal is showing signs of being over at the knees, the rate of growth should be modulated and caloric intake should be reduced.

    Physistis

    Physitis or inflammation of the growth plate is usually seen at the distal end of the radius or tibia, or within the distal end of the cannon bone.  It is seen as puffiness in the affected joint and may be associated with heat and swelling.  Physitis is typically seen in foals on too high of a plane of nutrition, or in foals being fed for rapid growth.  If the foal is still nursing, the mare may actually be contributing to the development of physitis.  Some mares are simply better milkers than others.  Suggested management techniques may be to discontinue any creep feeding of the foal, or do not allow them access to the mare’s feed.  In addition, the foal may be muzzled periodically to decrease his milk intake, or the foal may be weaned and put on a less calorie-rich diet.

    Osteochondrosis

    Osteochondrosis or OC is caused by a failure of the endochondral bone (the bone underlying the cartilage) to properly ossify.  Bone growth occurs first with the growth of cartilage which is then replaced by bone. If this fails to happen, essentially the bone has a weakened area underlying the cartilage.   It can cause further development of bone cysts or osteochondrosis dissecans (OCD). While these terms are often used interchangeably, OCD refers to a flap of cartilage displacing away from the joint surface.  Causes of OC in young horses are quite diverse and include dietary mismanagement, traumatic injuries, inadequate or excessive exercise, genetics, toxicities, body size, and growth rate.

    Osteochondrosis: Is it the end of the world?

    One of the interesting things about this disorder is how frequently it may actually appear in the equine population.  Many figures are given, with some stating that 20-25% of European foals will develop an OC (Barnevald and van Weeren), while others have found an incidence of 32% in Hanoverian Warmbloods.  However, in the latter study, there was no correlation between radiographic findings of OC and lameness. Indeed, in a recent study of Dutch Warmblood horses presented for a pre-purchase exam, 44.3% of clinically sound horses were found to have OC lesions  (Voss).  Therefore, even if your foal has radiographic evidence of lesions, unless accompanied by joint effusion or lameness or presenting as fragmentation within the joint, it may never represent a soundness issue.

    Next month we will look at what we can do to try and prevent our foals from acquiring any of these development orthopedic diseases.


    Voss, N.J. 2008. Incidence of osteochondrosis (dissecans) in Dutch Warmblood horses presented for pre-purchase exams.  Irish Veterinary Journal. 61:1)

     

     

    What is the difference between premature and dismature?

  • Protein Nutrition VI: The Growing Horse

    Written By Dr. Kris Hiney

    Previously we have discussed important concepts in protein nutrition concerning amino acids, digestibility, site of digestion as well as the requirements for several classes of horses. However, we have not yet looked at the young growing horse. This month we will discuss the protein needs of horses from weaning to two years of age, and examine some typical equine diets to determine if they fulfill a young horse’s protein requirements.

    The protein source used to meet our horse’s amino acid requirement is especially important in the growing animal. Young horses are usually the model used to test protein sources, as researcher’s can monitor the average daily gain of the horses. Ideally, the amount of calories and protein does not different between the horses, only the protein source. These diets are referred to as iso-nitrogenous and iso-caloric. The horses which are able to achieve greater rates of growth are doing so presumably because the amino acid profile of a particular protein source more closely matches the needs of the young horse’s body for protein synthesis. In fact, in 4 month old horses, milk protein supported greater rates of growth than did other sources including linseed meal, soybean meal or barley. This would certainly make sense, as one would expect that the amino acid profile in milk designed to support foal growth would do so better than plant proteins!
    With young horses, it is especially important that we try to eliminate deficiencies of amino acids which limit growth. Again, those amino acids which are deficient in the diet are refereed to as the liming amino acids. For horses (along with many domestic livestock species) the most important limiting amino acid is lysine. For young horses, it is recommended that lysine make up 4.3% of the total protein consumed in the diet, or alternatively, that the young horse between 4-10 mo of age receive 33-42 g of lysine per day. The young horse may even need to consume less total protein, if key amino acids are supplemented in the diet. Threonine has also been shown to limit young horse growth, and supplementation of this amino acids as improved growth rates, as well as lowering serum urea nitrogen. A decrease in serum urea nitrogen indicates that the animal is undergoing less catabolism or breakdown of amino acids, and using them instead for protein synthesis. If an animal is fed a poor quality protein, with a bad amino acid composition, the horse will still be able to use those amino acids, but only for energy or storage as fat. As part of this process, the nitrogen of the amino acid is removed and incorporated into other amino acids, or into urea for later excretion. Thus when an animal has a higher blood urea nitrogen, it indicates poor protein utilization.
     
    In Table 1, the amount of crude protein needed per day is given for horses up until 18 months of age. For simplicity's sake, ages of horses are grouped, rather than each month’s requirements listed. As such the higher value for grams of crude protein is listed for the age range. This was preferred rather than taking an average value, and underfeeding protein. However, you can see that the young growing horses’ protein requirements begins to decrease as it reaches its yearling year. If we relate that to the increase in size of the young horse, the concentration of protein needed in the diet decreases as well. It is the early rapid growth that requires the greatest amount of protein that the horse will ever need through its lifetime. Table 2 illustrates the amount of crude protein necessary in the total diet in order to reach the young horse’s requirements. As the horse matures, the amount of crude protein needed in the diet declines. It is also easy to see that allowing the foal to ingest greater amounts of feed, requires a lower concentration of protein needed in the diet, and a more conservative approach to protein intake.
    Expected mature weight (lbs)
    4-6 mo.
    7-8 mo
    9-10
    11-12 mo.
    13-15 mo
    16-18 mo
    900
    553
    587
    620
    692
    684
    664
    1000
    614
    651
    688
    768
    759
    738
    1100
    676
    717
    758
    846
    836
    820
    1200
    737
    782
    726
    922
    912
    885
    1300
    798
    846
    894
    998
    987
    959
    Table 1. Protein requirements (g/d) for young horses based on their expected mature body weight.
    % of Bwt consumed
    4-6 mo.
    7-8 mo.
    9-10 mo
    11-12 mo
    13-15 mo
    16-18 mo.
    2.0
    20
    15.1
    13.8
    13.8
    12.5
    11
    2.25
    17.8
    13.4
    12.3
    12.3
    11.1
    9.8
    2.5
    16.0
    12.1
    11.0
    11.0
    10
    8.8
    Table 2. The total percent crude protein needed in the diet for a growing horse.
    These values are based from the total intake on a dry matter basis. The change in body weight of the foal is taken into account. For each age grouping, the smaller weight of the foal (i.e., a 4 mo old foal would weigh less than a 6 mo. old foal) is used in order to ensure adequate protein intake.
    When feeding your young horses, it is always important to start with a good quality hay. Ideally you are using a legume hay or at least a legume grass mix. If the young horse has access to good quality, growing pasture, this also supplies an excellent source of protein. However, this does entail pasture maintenance. When a plant is in a younger stage of maturity, or actively growing, its protein content will be higher. If the foal is forced to graze mature stands of grasses, or even weeds, the protein content will be lower. Let’s work through a few examples in order to demonstrate the type of diet the foal will need.
    Let’s begin with a foal that we expect to mature out to 1100 lbs. He is currently 6 months of age, so we know that he should be receiving 676 g of protein per day. At this age, the foal should weigh 473 lbs. We have a grass legume hay mix which supplies 16% crude protein. If we look at table 2, we can see that our foal should receive enough protein if he is fed at 2.5% of his body weight per day, or 11.8 lbs of hay per day. If he eats more, he will definitely meet his protein requirements. But let’s make this a little more complicated. We decide to only feed him 2% of his body weight in hay per day. He now receives 9.5 lbs of hay per day.
    Doing the math, our hay provides: 9.5 lbs /2.2lbs/kg = 4.3 kg
    4.3 kg x 16% = 688 g of crude protein.
    That meets his requirements as listed in the table above. Why is that? Again, for simplicity's sake, the table uses the lowest weight possible for each group of horses. Therefore, the actual total protein needed in the diet is slightly less than for the 4 month of foal. Essentially, if receiving a good quality legume hay, your foal will be adequate in protein. However, what if the hay has a greater proportion of grass, or the hay was cut at a later stage of maturity? To explore this possibility, we will feed a hay that only contains 13.5% crude protein.
    Following the same procedure as above:
    4.3 kg x 13%= 559 g of crude protein.
    We are now deficient in protein. We also might need to be concerned that our amino acid profile may be poor for a young growing horse. So let’s look at two different alternatives.
    We can use a commercial feed that supplies 15% crude protein to our horse on an as-fed basis. Previously we were calculating our feed values on an as-fed basis. We will continue with the concentrate by staying as-fed, as is seen on the feed tag. How much grain will we need to supply the foal as we are only deficient by 120 g of crude protein?
     If we divide the amount of protein needed by the percent protein in the feed :  120g /16% ; we need 750 g of the feed. Converting that to pounds, and our horse needs to eat 1.7 lbs of grain per day. That certainly does not seem like an excessive amount of grain for our young horse per day. In fact, he is still below the total 2.5% of his body weight. So what does this mean overall? Choosing higher protein hays will ensure your foal has the adequate amounts of protein for higher growth. If your hay offers less protein, a commercial feed designed for young horses will typically easily meet the deficiency in that hay. Additionally, when examining these feed tags, you will often see that some of the key amino acids are supplemented in that feed. This ensures that your foal will grow optimally, provided nothing else is going wrong!

     

  • Protein Nutrition V: Broodmares

    Written By Dr. Kris Hiney

    This month we will continue our protein nutrition series with the classes of horses having the most demanding protein needs: the broodmares. It would make sense that this group of horses is the most sensitive to changes in protein nutrition, as they are continually supplying nutrients for the growing fetus or foal. Shortchange your mare and you may be short changing your future generation. But let’s take a look at what these animals need, so that we can avoid any potential pitfalls in our feeding strategies.
    Gestation
    Before we start feeding a mare for gestation, we at least need to get her pregnant first. Therefore proper nutrition of the broodmare does start before conception. As long as the mare is fed adequate amounts of protein (no higher than required by a maintenance horse) there should be no nutritionally related reproductive issues. However, mares which are deficient in protein are slower to begin cycling normally and have a higher rate of early loss of pregnancy. Short changing the mare on the feed bill will definitely not save money in the long run. Always begin the breeding season with a proper feeding program for optimal results.
     After the mare has conceived, her early pregnancy requirements are not much different from when she was open. Just like with her energy needs, her changes in protein requirements are really quite minimal at the beginning of her pregnancy. As the rate of growth of her developing fetus increases, she must have a greater supply of amino acids in her diet. Looking at Table 1, you can see that the greatest increase in her protein requirements occurs in the last two months of pregnancy. Table 2 places these daily requirements into a simpler expression of the total percent protein that your mare will need depending on the amount of feed she is consuming.  Just as you can imagine, the more the mare consumes, the lower the total percentage of crude protein needed in the diet.  In fact, this is usually what happens. Most mares will voluntarily consume more feed as her energy needs go up, thus also meeting her protein requirements.
     
    Shopping for Feeds
    It might be surprising to look at the values in Table 2 compared to the typical amount of protein present in a commercial feeds.  Most feeds designed for broodmares range between 14 and 16% crude protein, yet the overall protein percentages needed in the diet are much lower. So why do feed manufacturer’s offer such high levels of protein in their products?   For one, most of the feeds are really designed to meet the needs of the lactating mare, rather than the gestating mare. Additionally, you may remember from earlier articles that forage protein is not digested as fully as the protein which comes from concentrates. While protein requirements do try to account for some of this variance, an average digestibility value combining both forages and concentrates is used to calculate the total amount needed in the diet. Furthermore, the guidelines for protein intake are based largely from research with horses consuming mixed diets usually offering an equal proportion of concentrates and forages. Thus if more of your horse’s diet is forage, you must consider that when selecting an appropriate concentrate.   Remember as well, that legumes are digested to a further extent than grass hays, thus also offering not only more protein on a concentration basis, but also being absorbed more thoroughly by the horse. A general guideline would be, that if feeding high quality legume hays, the amount of protein required in the concentrate could be much lower (as low as 10-12% CP). If feeding primarily grass hays, then you should select a concentrate closer to 14% CP.
    Wt of horse (lb)
    Early gestation
    5 mo.
    6 mo
    7 mo
    8 mo
    9 mo.
    10 mo.
    11 mo.
    900
    507
    551
    566
    586
    611
    641
    676
    718
    1000
    562
    611
    628
    650
    677
    711
    750
    796
    1100
    619
    673
    691
    715
    746
    782
    826
    877
    1200
    675
    754
    755
    781
    814
    854
    902
    957
    1300
    731
    794
    817
    845
    881
    924
    976
    1036
    Table 1. Protein requirements (g/d) for a gestating mare based off her initial non-pregnant weight.
    % of Bwt consumed
    Early
    5 mo.
    6 mo
    7 mo
    8 mo
    9 mo.
    10 mo.
    11 mo.
    1.5
    9.6
    10.4
    10.7
    11.0
    11.5
    12.1
    12.8
    13.6
    1.75
    8.2
    8.9
    9.1
    9.5
    9.9
    10.3
    10.9
    11.6
    2.0
    7.2
    7.8
    8
    8.3
    8.6
    9.1
    9.6
    10.2
    2.25
    6.4
    6.9
    7.1
    7.4
    7.7
    8.1
    8.5
    9.0
    2.5
    5.7
    6.2
    6.4
    6.6
    6.9
    7.3
    7.7
    8.1
    Table 2. The total percent crude protein needed in the diet for a pregnant mare throughout gestation. These values are based from the total intake on a dry matter basis. However, percent total protein is represented on an as fed basis, as is represented on feed tags.
    Protein requirements for Lactation
    The lactating mare will consume more feed than the typical maintenance horse as her energy demands have increased greatly.   Just like with energy, it is the lactating mares who really have the biggest nutritional demands of any of our horses. Compare the grams of protein needed per day in Table 3 to Table 1. You can see that her protein needs have more than doubled. If mares are deficient in protein, they will be unable to produce as much milk as those at an adequate plane of nutrition, and may end up losing weight. This is certainly undesirable, as this is also the time period when most mares are being rebred as well.   Mares do a fairly good job of producing milk though certainly not equivalent to a Holstein cow! Mare’s milk production usually averages about 3% of her body weight, with that value tapering off to about 1.9% of her body weight during late lactation. The protein concentration in the milk is the highest during the first 22 days of lactation (when foal growth is very rapid) and thereafter plateaus throughout the rest of her lactation.
    Wt of horse (lb)
    Early lactation
    3mo.
    4 mo
    5 mo
    900
    1234
    1180
    1124
    1069
    1000
    1369
    1309
    1247
    1186
    1100
    1507
    1441
    1372
    1306
    1200
    1646
    1573
    1498
    1426
    1300
    1781
    1702
    1621
    1543
    Table 3. Crude protein requirements in grams per day for the lactating mare.
    % of Bwt consumed
    Early Lactation
    3
    4 mo
    5 mo
    1.5
    24.1
    23.0
    22.9
  • The Mare in the Middle

    Written By Barbara O'Brien

    “Some people can’t be trusted.” At least that is what my son, Wes, would tell you about me and my husband, Kevin.  What started out as an innocent, overnight trip to celebrate our 29th anniversary quickly turned into a horse rescue adventure. Now, we need another horse like we need a hole in the head. We were up to fourteen a few years back and were now down to eight. This has proven to be a nice, manageable number with a good mix of young and old.

     

    When we left that day, Wes, ever the eldest, warned us, “Now, don’t get into trouble, you two.” How much trouble could a middle aged, small town couple that didn’t smoke, drink or gamble get into?” I thought. I must tell you, we are actually pretty boring. We usually get a room at a B & B, have a nice dinner at the Branding Iron, and then spend the next day poking around antique shops. I forgot that Kevin and I are dangerous when we are away from the responsibilities of the farm and family.

     

    As we were driving to the Preston/Chatfield area in Southeastern Minnesota I mentioned to Kevin that I had seen a post on one of my horse internet forums about a herd of over 40 Morgan Horses that needed to find new homes quickly or they ran the risk of being sold to a slaughter broker.

     

    It was a just a casual comment, but Kevin was intrigued. He has the biggest heart in the world and this is why he is not allowed in animal shelters. “We don’t need another horse,” I said.  “I only mentioned it because I think it’s sad to see someone lose their farm and have to sell all of their carefully bred horses.”  “Where are they he asked?” “Mason City, Iowa,” I replied. “How far is that?” he wondered. “Only about 100 miles from where we are staying tonight.” I could see him thinking about it. “Let’s go see them,” he said finally. “Why? You know we would want to bring at least one home.” “Com’on, it will give us something to do tomorrow.” His eyes lit up like a little boy who has a wonderful plan in mind. “You don’t want to go back right away do you?”

     

    I need to preface that last sentence for you; you must understand that, because we have kids and animals, we never go on any real vacations. This one night, annual get away to an area only about 70 miles from our home is the only non-work trip we take. We would do anything to not have to go right back. We like to drag out the experience as long as possible, usually not arriving home until well after chore time.

     

    “Besides,” Kevin continued, “you can take some pictures for them and that may help the horses place faster.”  I looked at my ever-ready camera and had to agree. More pictures are always better than fewer. And the rescue group’s most recent pictures were taken during a snowstorm, so they might appreciate a few more with better light.

     

    We mulled the idea over dinner and then I contacted the rescue group and they said they would be thrilled to have us meet the horses. That night, at the bed and breakfast, just as we were about to go to sleep, we both swore that we would only take pictures and not bring home any horses. Absolutely not!

     

    The next morning, we drove to Mason City, Iowa, where Kathi Ring, of Gentle Spirit Horses, the rescue group, was waiting for us. She introduced us to the owner. He was an older gentleman, who, because of a death in the family and facing eminent foreclosure, was being forced to sell the horses. We felt bad for him, as the herd represented over 30 years of some of the finest names in the Foundation Morgan horse world. He had been offered $250 per horse by a slaughter broker, but chose instead to ask Gentle Spirit for help.

     

    Since he had lost his farm, the stallions and young stock were being housed at two adjoining feedlots and the broodmares were in a small grass pasture. With my camera in hand and Kevin ready to assist we went into the lot with the 2-7 year old mares and geldings.  We had been warned that they had not been handled much, but within moments, we found ourselves being mobbed.  Bays and blacks, buckskins and chestnuts and even a grulla came to see what we doing. They sniffed us and many allowed themselves to be scratched. My camera and the fact that I was crouching to get a better angle fascinated them.  Kevin was surrounded by curious youngsters as he unfurled the disk shaped reflector we use to bounce light on a subject.

     

    I tried to shoot as many as I could but it was hard to get individual horses, as they naturally stayed together in tight little bunches. I settled for grabbing a few headshots of as many as I could. The young horses were all very sweet and well bred of course, but it was easy to walk away. With their breeding and temperaments, I told myself, Gentle Spirit would have no trouble placing them.

     

    We then went out to the pasture that held a group of bred broodmares, three young stallions and mare with her foal.  They were also curious about us and came up to be petted. I spotted a mare with palomino foal lying in the corner of the field and managed to get a few shots of them before they got up.

     

    As I left the mare and foal and was framing my next shot, a particularly lovely bay mare walked right up to me. She was accompanied by her offspring, a two year old bay filly and a yearling buckskin stud colt. I scratched her chest and told her she was good mother and then moved on, hoping to get all the horses done before we lost our light. This merry trio, with the bay always in the middle, began to follow me around the pasture. Almost every time I tried to take a picture, the bay mare rudely interrupted me, by nosing my shoulder.

     

    It was then I looked deeply into her kind eye and I knew in my heart it was all over. This mare would have to come with us.  Now, I work with animals all the time. There have been countless puppies and kittens from animal shelters, and I even occasionally help out other horse rescues so I am pretty immune to their plight. I have managed to harden myself to their advances, as I must keep my numbers manageable. It wouldn’t be fair to the animals if I had more than I could love and care for. But this mare was special, and she was doing everything in her power to tell me that she was supposed to be mine. 

     

    Maybe the universe told her that we had lost our beloved bay Morgan mare, Cinder, to cancer two years ago. Or perhaps my first horse, who, coincidently, was a small bay Morgan mare that looked just like her, whispered to her from horse heaven. It was like she knew… and I’d have to agree, I knew it too.

     

    I didn’t say anything to Kevin although I could see he liked her also. She wasn’t even halter broke but she let me pick up her hoof and moved softly away from pressure when I asked. We finished up with the stallions in the front lot and said our thank-yous and good-byes to Kathi and the owner. We didn’t say much on the way home and, anyway, I was doing a rough edit of the images on my laptop. As I viewed the images, I was struck by how kind the eyes were of every horse I photographed. They were intelligent, curious and so typically Morgan. I hoped my efforts would help them get new homes.

     

    My mind kept drifting back to the mare. She was so sweet and kind. Even though she was not broke, I knew it wouldn’t take much to bring her around. Morgans are, as a rule, willing and thoughtful horses. They are the Border Collies of the horse world. Give them a job to do and they will do it. And they will enjoy doing it, too.

     

    That night, after dinner and chores and we were settled in, I said to Kevin, “We really don’t need another horse.” He looked down and slowly shook his head. “Agreed?” I asked. “Agreed,” he said sadly.

     

    I tried to sleep but I was still thinking about the mare. I knew that we were doing the right thing. We can’t go along rescuing every poor horse we see. As one of my other sons, Warren, would say, I was letting my “impulses pirate my thought processes”.

     

    Suddenly, I had the image of Kevin as a pirate in my mind, “Arrgh!! Lassie, she is a fine horse and we should go and get her,” he growled in his best pirate voice. “But we have enough already,” I protested weakly. “No, me fine Lass, you can never have enough horses. Let’s set sail for Mason City, Iowaay and bring her home. Arrgh!”

     

    I tossed and turned and finally fell asleep. The next morning I woke up to a horse snorting and nickering outside my window. It was exactly the sound I hear when the horses have gotten out and are wandering around.  I ran to the window and looked out and saw the bay mare standing in the yard below with my other Morgans. She was flanked by Beauty and Finn, once again in the middle. “How did you get here?” I wondered, and then I woke up. I had been dreaming all along. Was it some kind of sign? Kevin heard me moving and was soon awake himself. I looked at the clock. It was only 5:00 am.

     

    “Barbara?” he said quietly. “Are you awake?”

    “Yes,” I replied.

    “I think we should get the horse.”

    I breathed a sigh of relief. “Me too,” I whispered. “Me too.”

    “Agreed? He said. “Agreed,” I said.

     

    Later that morning I contacted the rescue and sent them the check to bail my mare out.

    She will be arriving just in time for Christmas. When I told Wes about it, he laughed and said, “I knew it! I just can’t trust you guys. You always get in trouble when you go out of town.”

     

    I haven’t named the mare yet. The rescue is still working on identifying who her parents are and who the sire is of the foal she is carrying. It really doesn’t matter to me. I

    know her heart, and she knows mine, and she will tell me her name soon enough.

     

     

    If you would like to help with the Gentle Spirit Horse's rescue/placement efforts you can find more info here:

     

    http://www.facebook.com/pages/Gentle-Spirit-Horses/149994561712125

    and here:

    http://www.gentlespirithorses.com/

     

     

     

     

     

     

     

     

     

  • Protein Nutrition IV: Protein for the Working Class

    Written By Dr. Kris Hiney

    Last month we learned that meeting a mature idle horse’s protein requirements are surprisingly easy.  If a horse is provided with good quality hay at 2% of its body weight it can easily consume enough protein even without eating concentrate.  However, if forage quality is low, adding a supplemental designed to provide essential amino acids can easily make up the difference.

    But my horse works hard!

    But what about if your horse has more of a job to do than just stand in his pasture and eat?  Many people automatically reach for a higher protein feed once their horse goes to work, but is that really the right thing to do?  Of course protein requirements of a working horse do go up due to the increased tissue turnover and repair associated with exercise.  Further, horses also lose nitrogen through sweating and increase muscle mass with training.  However, the increase in protein required pales in comparison to the increase in calories needed.  High protein diets increase the need for horses to excrete urea (the form in which excess nitrogen is removed from the body) and may alter their acid base balance. While horses seem to be able to handle the increased need to remove nitrogen from higher protein diets quite easily, it will result in more urine excretion.  Thus more ammonia may build up in poorly ventilated buildings and bedding costs will go up.  In fact, it may be beneficial to feed a lower total protein amount to the horse while providing key amino acids.   In one study, horses fed a lower protein diet but supplemented with lysine and threonine had higher blood pH values after exercising compared to horses on a higher protein diet (Graham-Theirs et al., 2001). When horses exercise intensely they produce lactic acid.  Lactic acid drops the pH in the blood and can contribute to the onset of fatigue. Therefore this lowered protein diet may protect against a drop in blood pH and therefore allow the horses to exercise longer or recover faster.  However it should be noted that the lower protein group was also supplemented with fat as well, clouding interpretation of results.

    So how much do they really need?

     Table 3 shows the total amounts of protein needed, while Table 4 again expresses this on a % protein basis.  You can see that most performance horses will do quite well if you select a feed between 10-12% crude protein.  Remember that when selecting a feed, you must consider your forage source first!  For example, if your performance horse was eating a primarily alfalfa hay with a value of 16% crude protein, his protein needs would already be met!  Selecting a concentrate then would primarily serve to supply any additional energy needs the horse may have.

    Table 3.  Crude protein requirements for work (g of CP/d).

    Wt of horse (lb)

    Light

    Moderate

    Heavy

    Very Heavy

    900

    562

    617

    693

    808

    1000

    624

    685

    769

    896

    1100

    687

    754

    846

    986

    1200

    750

    823

    924

    1077

    1300

    811

    891

    1000

    1165

    Table 4.  Percent total protein required in the diet on an as-fed basis depending on the total consumption of the horse per day.

    % of Bwt consumed

    Light

    Moderate

    Heavy

    Very Heavy

    1.75

    9.3

    10.3

    11.6

    13.5

    2.0

    8.2

    9.0

    10.1

    11.8

    2.25

    7.3

    8.0

    9.0

    10.5

    2.5

    6.6

    7.2

    8.1

    9.5

    Let’s do math!

    Now let’s put this together in a practical problem.  We will feed an 1100 lb horse 2% of his body weight in grass hay.  Our grass hay has 9% crude protein value on a DM basis.  We weigh out 22 lbs of hay for our horse per day but we weigh it on an as-fed basis (meaning what it weighs on a scale that day).

    First we will convert our weight of hay to the weight of our hay on a dry matter basis.  We will assume the hay is 85% dry matter.

    22 lbs x .85(% dry matter) = 18.7 lbs of hay on a dry matter basis

    Then we will convert our lbs to kilograms.

    18.7 lbs /2.24 = 8.3 kg of hay

    Multiply that by our percentage of protein.

    8.3 kg  x .09 = 747 g of CP.

    Let’s check this horse’s lysine requirements as well.  Remember that the only value for amino acids required by the horse is for lysine.  The current available knowledge suggests that horses need 4.3% of their protein to come from lysine.  Typically grass hays are fairly low in lysine compared to legume hays.  An average grass hay harvested at a mature stage is 0.38 % lysine.  Again we multiply the amount of hay fed 8.3 kg x .0038 = 31.5 grams of lysine.  Our maintenance horse only needs 32 grams of lysine.  We therefore have met his requirement by feeding this hay.

    Even if our 1100 lb horse is in moderate work we are short by only 7 grams of CP.  This can easily be met by any additional concentrate or by simply eating more hay.  However, if we move him up in work, we become much more deficient in protein as well as lysine.  Let’s assume he is now in heavy work and deficient by 100 g of protein.  We want to add 3 lbs of concentrate (which isn’t very much) to his diet.

    3 lbs /2.24 = 1.3 kg of feed

    We need our 1.3 kg to supply 100 g of CP.  So our feed needs to be 100g/1300 g of feed = 7.7 % CP on a dry matter basis. On an as fed basis, this would be 9% CP.  Almost every commercial feed will contain this level of crude protein.  Hopefully we have now illustrated that there is no need to feed a high protein feed designed for growing horses or broodmares to our exercising horses.

    In summary, protein requirements for maintenance horses or even those at work are fairly easy to meet by a normal horse diet.  If feeding a poor quality hay, you may have to supplement your horse’s diet.  If so, then choose a feed that contains legumes (like alfalfa meal) or a concentrate that contains a high quality protein like soybean meal.  While no clear amino acid recommendations are available for working horses, there appears to be some benefits of feeding lower total quantity of protein while supplementing with key amino acids.  This certainly does appear to be the future of equine research concerning protein nutrition.

    Next month we will address the protein needs of the groups of horses which need the most attention: the growing horses and the broodmares.

  • Protein Nutrition III: Determining Protein Requirements for Your Horse

    Written By Dr. Kris Hiney

    In the last two articles we discussed the importance of protein quality, not only in terms of site of digestion in the horse, but also the amino acid composition of that feed.  Now we will try to simplify these concepts into selecting appropriate feeds for horses.

    The first task in developing a feeding program for your horse is to identify what class of horse you have.  (For a review revisit: Equine Energy Requirements and Energy Requirements for the Working Class)  The horses with the lowest protein requirements relative to their body size are the mature horses not in work, or maintenance horses.  This does not include geriatric horses which may have altered protein needs due to the lowered efficiency of their digestive system.  We also must assume that the horse is receiving enough calories in the diet.  A horse fed a diet sufficient in protein, but low in calories will lose weight (makes sense right?) but a horse which has adequate calories but not enough protein can also lose weight.  We also make some consideration for the activity level of the horse as well.  Remember the difference in energy requirements  between the couch potato Quarter Horse and the active Thoroughbred mare (Equine Energy Requirements)?  Well a similar relationship exists with protein requirements.  Essentially the more active horse would have more lean tissue/muscle  to support than the lazy horse.   Table 1 lists the actual protein requirements for a  maintenance horse depending on activity level and their body weight.  Remember that this does assume a quality protein source. Lower quality protein (less digestible or poor amino acid profile) can adjust these figures upwards.

    Table 1.  Crude Protein requirements for maintenance (grams of CP/d) based on average activity level.

    Wt of horse (lb)

    Couch potato

    Average

    Active

    900

    434

    507

    579

    1000

    482

    562

    642

    1100

    530

    619

    707

    1200

    579

    675

    772

    1300

    626

    731

    835

    What percent protein do you need?

    But let’s put these numbers into something more people are familiar with, percent of the diet.  Table 2 provides the percent protein of the total diet a horse would need to consume to meet their protein requirements.   Looking at Table 2 shows how easy it is to meet a maintenance horse’s protein requirement.  You can also see that as total consumption goes up, the percent of the protein needed in the diet goes down.  Conversely, if you fed less you would need to increase the percent protein in the diet.  Horses will usually consume between 1.5 and 2.8% of their body weight per day on a dry matter basis.  Typically you will see horses lower their consumption of less palatable hay which often equals poor quality.  However, this can largely be based on the individual, as some horses compensate by lowered feed quality by increasing intake (Edouard et al., 2008).  It turns out that horses are much more variable in their voluntary intake than other domestic species are!  Just like a horse to always want to be unpredictable. If you notice your horse picking through its hay and leaving a good proportion of the hay untouched it may be wise to select a supplement designed to provide amino acids but not to greatly increase the calorie consumption by the horse.  Alternatively it may be time to find a new hay supplier (see Selecting Forages).

    Table 2a. Percent total protein required in the diet on a dry matter basis depending on the total consumption of the horse per day.

    % of Bwt consumed

    Couch potato

    Average

    Active

    1.5

    7.2

    8.4

    9.6

    1.75

    6.2

    7.2

    8.2

    2.0

    5.4

    6.3

    7.2

    2.25

    4.8

    5.6

    6.4

    2.5

    4.3

    5.0

    5.6

    Table 2b. Percent total protein required in the diet expressed on an as fed basis assuming an average dry matter content of 85%. Note: this can change with the feed fed and is only representative of harvested feeds, not pasture or grasses.

    % of Bwt consumed

    Couch potato

    Average

    Active

    1.5

    8.5

    9.9

    11.3

    1.75

    7.3

    8.5

    9.7

    2.0

    6.4

    7.4

    8.4

    2.25

    5.6

    6.6

    7.5

    2.5

    5.1

    5.9

    6.8

    Protein content of common horse feeds

    Now let’s look at some typical protein values for feeds.  To be sure of your own feed ideally have your forage tested as well as examine your feed tag.  Corn ranges between 8-9 % CP on a DM basis, oats 12-13%, soybean meal – 43-49%, grass hays – 10-18%, and legumes between 18-25%.   With the range of protein content in forages, one can see how important it is to have knowledge of your nutrient content prior to selecting your concentrate.   Even with these ranges, most maintenance horses will easily meet their protein requirements by forage alone.  If you look at the range of percent protein needed by the maintenance horse in their total diet, it compares quite well with grass hays.  If you are feeding your horse and he is maintaining weight, he should easily be meeting his protein requirements at the same time.  Remember, we assume  the horse is receiving good quality hay.  If you are worried about the horse meeting its amino acid needs, many feed companies make supplements specifically designed to be fed with a strictly forage diet, rather than greatly increasing the concentrate intake.  For example, many feed companies offer protein supplements in the range of 30-35% crude protein.  These are designed to be fed at a minimal rate (only 1-2 lbs per day) in order to simply balance out any deficiencies from an all forage diet.  Clearly not all horses need the extra calories that come from feeding higher levels of concentrates.  This provides a convenient, easy way to ensure that your horse’s nutritional needs are being met.

    Next month we continue with protein nutrition in the exercising horse.

    Edouard et al.2008. Animal:An international journal of animal biosciences. 102:10:1526-1533.

  • Protein Nutrition, Part II Protein Quality - It's More Than Just Digestibility

    Written By Dr. Kris Hiney
    In the last article, we introduced the idea of examining the protein in our horse’s diet beyond just the mere percent crude protein on the feed tag or a forage report. We discussed the concept of protein digestibility and the importance of the site of digestion. As there is only limited evidence that uptake of amino acids takes place in the hind gut of the horse, we prefer to feed proteins which are digested and absorbed in the small intestine of the horse. Typically concentrates offer more pre-cecal digestibility of protein than do forages. Therefore site and extent of digestion are key components of protein quality. However, there is another equally important factor in protein quality, and that is the amino acid profile.
    Last month the amino acids that horses could synthesize on their own were listed, as well as the amino acids that are essential to be supplied by the diet. Horses must receive the proper balance of amino acids in order to synthesize the many complete proteins in their body. When they do not receive enough of a particular amino acid, protein synthesis is limited. That amino acid is then referred to as the limiting amino acid. Typically, lysine is the most common limiting amino acid in the horse’s diet, or the one in shortest supply. It does not mean it is the most abundant amino acid found in the horse’s body, rather the one that is most commonly deficient in feeds. Now remember, every protein in the body is coded for by the DNA that provides a blue print to build that protein. The DNA provides the proper sequence of amino acids that must be linked together to form the protein. Let’s say that to build one molecule of actin (a protein found in muscle cells responsible for their contractile activity) there are 25 lysines, 30 threonines and 46 alanines. (The actual polypeptide chain of actin is over 300 amino acids long.)    If the diet contained only enough for 20 lysines to be added to the peptide chain, protein synthesis would halt, even if you had 35 threonines. If you added those lysines back in through the diet, protein synthesis could continue. Now, this is an arbitrary example, instead try to think of protein synthesis occurring throughout the body, constantly adding amino acids that have come from the diet, synthesized by the horse, or that have been recycled by tearing down old proteins.   Obviously the more protein the horse is synthesizing (think young growing horses) the more critical the amino acid profile of the diet.

    DNA molecule which contains the information to build every protein in your horses body.
    http://www.stern.de/_content/50/44/504448/dna_500.jpg
    So what is the amino acid profile? Simply put, it is the percentage of each amino acid that appears in the diet, or even in a horse’s tissue. For example, in equine muscle tissue, lysine is set at a relative value of 100%, while other amino acids such as arginine, leucine, phenylalanine and threonine appear at 76, 107,60 and 61% respectively of the amount of lysine present in muscle(Bryden, 1991). In other animal species such as swine and poultry, nutritionists try to match the amino acid profile of the diet to the amino acid profile of the actual animal. In this manner, the least amount of amino acids are wasted. Instead, they are incorporated into the animals’ body to allow for growth, reproduction etc. One of the goals of many animal nutritionists is to achieve something called zero nitrogen balance in the animal. That means the amount of N going into the animal matches the amount of N going out of the animal. Or we are replacing the amount of N that is being lost by the animal through normal tissue turnoever. If we feed protein beyond what the animal requires, the animal will still digest and absorb those amino acids. However, if they exceed the horse’s requirements to synthesize protein, the horse will instead catabolize those amino acids for fuel, and excrete the nitrogen in the urine as urea. If you have ever walked into a poorly ventilated barn with horses that were fed high protein diets, you probably have smelled the ammonia that comes with excessive protein feeding. Furthermore, feeding excess N just adds to the N being added back to the ground through runoff from facilities.
    Protein quality and it’s amino acid profile can alter how much protein the horse actually requires. While we often just discuss protein requirements generically as a percentage, in fact horses can be fed a lower total amount of protein if it is of higher quality. For example, in young horses, the lysine requirement is 4.3% of their crude protein requirement.    The higher amount of lysine in the feed, the less of that feed will need to be fed. Let’s take a 4 month old foal which requires 669 grams of CP and 28.8 g of lysine. We then feed our horse either a 16% crude protein feed of high or low quality. We feed him at 2.5 % of his body weight and he weighs 370 lbs. That provides an intake of 9.25 lbs per day. If his feed provides 16% protein, he gets 660 grams of protein. We have almost completely met his protein requirements. But what if one of our feed sources contained only 2% lysine? That means that the foal would be deficient by 15.8 grams (the feed would provide 13 g of lysine) and thus his growth rate would be limited. Therefore the foal would have to eat much more of that diet (more than he can consume) in order to consume the correct amount of lysine. Our foal on the high quality diet would receive 28 g of lysine, meeting his requirements, and allow his body to grow normally. In older horses whose protein requirements are easier to meet, we can actually lower the total amount of protein in the diet provided it is of a high quality. In fact, lowering the total protein in the diet while supplementing key amino acids has been proven effective in both growing horses (Graham et al., 1994, Stanier et al, 2001) and in exercising horses (Graham-Thiers et al, 1999, 2001)
    The future of protein nutrition in the horse may very well focus on identifying the correct amino acids needed in the horse’s diet, and moving to a lowering of the absolute % CP in the diet, therefore minimizing waste, and decreasing the amount of N added back to the environment. While nutritionists still have much to learn, the goal when feeding protein is to feed just the right amount the horse needs, and not to overfeed needlessly.
    Next month, we put the theories into practice and discuss protein requirements for various classes of horses.

  • Protein Nutrition, Part I: Protein Digestion in the Horse

    Written By Dr. Kris Hiney

    This month we begin a new series focused on protein requirements for our horses, and the various feeds which provide protein. Protein is commonly the first concern of many horsemen when selecting their feeds, and the most frequently discussed. In the equine industry, there tends to be a common fallacy that if a product costs more, it clearly is a more desirable product to feed. As feedstuffs which contain more protein are often more costly, this tends to make higher protein feeds more attractive to the consumer. However, that higher protein content may not be necessary to feed to your horse! Before we can delve too deeply into the proper amounts of protein to feed to the various classes of horses, we should back up and break down what protein does for the animal, and examine how the horse digests this very important nutrient.

    Proteins are actually complex molecules that are comprised of a series of amino acids joined together by peptide bonds. All proteins are built from a specific series of the 20 most common amino acids. While many more amino acids are found in nature, we typically limit our discussion of amino acid nutrition to these basic 20 amino acids.  Of these amino acids, some are characterized as dietary essential amino acids or non-essential amino acids. The dietary essential amino acids include lysine, methionine, phenylalanine, the branched chain amino acids (valine, leucine and isoleucine), tryptophan, threonine, histidine and arginine. The distinction between these two classes is that mammalian systems lack either the ability to synthesize some amino acids (they lack the appropriate synthetic enzymes) or they cannot produce enough of that amino acid to support normal bodily function. The non-essential amino acids can be produced in the animal’s diet from other amino acids. In contrast, bacteria can produce all amino acids. This is what gives the ruminant animals such as cattle, sheep and goats, such a unique advantage. They can rely very heavily upon bacterial synthesis of amino acids to meet their requirements.
    Figure 1. The levels of protein structure from primary (just the linear chain of amino acids) up to the completely folded, functional proteins.
    http://barleyworld.org/css430_09/lecture%209-09/figure-09-03.JPG
     All animals, in addition to plants, bacteria and fungi produce a wide array of proteins necessary for normal function. These include structural proteins found in muscle, bone, cartilage etc., enzymes, hormones, antibodies, and cell signaling molecules. The specific make up of a  protein is coded for by the organisms DNA. The DNA contains billions of individual genes that contain the information on how to build each specific protein found in the organism. Different tissues will turn on or express different genes, thus making liver produce the necessary proteins for its function, and the heart a separate set of proteins. However, every cell will contain the genetic information to produce every protein. That is why you can use a skin cell to clone an entirely new animal. All the necessary information to make a new horse is contained in that one cell. While this information may not seem germane to feeding horses, it is important to understand why the animal must receive particular amino acids in the diet. Without the right amount of essential amino acids, the animal is unable to synthesize protein correctly.
    When we feed protein, we need to be concerned with more than just the amount of protein contained in the feed. Feed tags will provide us with the percent of crude protein present in the feed. This number is really based on the percent of nitrogen found in the feed. That number is then multiplied by 6.25 to achieve the amount of crude protein. That is based on the fact that the average protein contains 16% nitrogen. However, there may be non-protein nitrogen present in the feed which may or may not be useful to the animal. While all protein contains nitrogen, not all nitrogen is protein. For example, in ruminant animals, non-protein nitrogen is often fed in the form of urea, due to the unique makeup of the animals digestive system which allows it to utilize these feed sources.  But what the crude protein percentage does not provide us with is information about  how useful is that protein to the animal. As horseman, we need to be concerned not only with the quantity of the protein we feed, but more importantly, with the quality.
    The quality of the protein can be thought of in two different ways. One indicator of protein quality is how digestible is that protein to the animal. A feedstuff which has a high percentage of protein that is unavailable to the animal, or is unable to be absorbed, is essentially useless. So let’s take a moment and explore protein digestion in the equine. Protein digestion begins in the stomach of the horse, where it is exposed to both inorganic acids (hydrochloric acid) and proteolytic enzymes – pepsin. These two digestive secretions begin the breakdown of protein by initiating the unfolding of the protein structure. While proteins are coded for by DNA in a linear form, the particular amino acids present in the protein cause the peptide chain to fold and wrap around itself to form its unique functional shape. In fact, one misplaced amino acid can render an entire protein useless. This is often the basis of many genetic diseases, a mutation which causes the wrong amino acid to be added to the peptide chain. Pepsin begins the disruption of the polypeptide chain by cleaving after specific amino acids, primarily tryptophan, tyrosine and phenylalanine. While gastric digestion does not completely break protein down to a point it can be absorbed by the animal, it shortens the polypeptides and allows more access to the enzymes which will be present in the small intestine
    As the dietary protein enters the small intestine, it will be digested much further by a series of proteolytic enzymes which arise from the pancreas. These include chymotrypsin, trypsin, elastase, carboxypeptidase etc. These enzymes essentially complete the breakdown of protein into small enough pieces that can be absorbed including single amino acids, dipeptides and tripeptides. Once these are absorbed into the enterocyte, the dipeptides and tripeptides are further hydrolyzed into single amino acids. These then enter the blood stream of the animal where they can be delivered to various tissues to be used for protein synthesis. Non-protein nitrogen can also be absorbed out of the small intestine of the horse. Feeding urea causes an elevation of blood urea nitrogen,as well as urinary nitrogen, as the animal flushes the nitrogen out of the animal’s system. There is no evidence to support the usage of feeding nonprotein nitrogen to the horse, as it is unable to be incorporated into bodily protein. 
    Sidebar: Foal management. The exception to protein digestion occurs right after birth. The foal is born with a naïve immune system and must receive antibodies from the dam. These come from ingestion of colostrum or the first milk a mare produces. The colostrum contains a trypsin inhibitor which prevents the antibodies which are present in the milk from being digested. The foal also helps out the process by having an “open gut”. The proteins initially presented to the gut can be absorbed intact through the process of pinocytosis, or engulfing of the entire protein by the gut cell membrane. However, there is a finite capacity of the gut to perform this action. The most efficient uptake of intact proteins takes place within the first 12 hrs, with relatively little to no absorption past 24 hrs. Additionally, there is a limit to how much protein can be absorbed. If a foal was first provided milk replacer prior to the administration of colostrum, they may not be able to absorb the important antibodies if fed later with the appropriate colostrum. So always make sure your foal receives high quality colostrum in the first 24 hours of life. Don’t skip straight to the milk replacer in an orphaned foal!
    Any protein which escapes digestion in the small intestine is then delivered to the hind gut of the horse, where microbial fermentation can take place. The microbes are quite adept at further degrading feedstuffs, and producing compounds that are of value to themselves, as well as to the horse. The bacteria in the hindgut of the horse are quite capable of synthesizing all of the amino acids, however there is little evidence this is useful to the horse. In contrast to the ruminant animal, whose site of fermentation and microbial protein synthesis is prior to the site of enzymatic digestion and protein absorption in the hindgut, the horse is unable to absorb these proteins. Unless the horse practices copraphagy, or the ingestion of feces, this protein is believed to be lost to the animal.  In horses infused with lysine either in the stomach or in the cecum, only gastric infusion resulted in an elevation of plasma lysine, indicating the inability to absorb lysine out of the hindgut. However, there has been some recent evidence that some absorption of amino acids may occur in the hindgut. Messenger RNA coding for specific amino acid transporters have been isolated from the hindgut of the horse. This indicates a potential ability of the horse to absorb at least some specific amino acids from the hindgut. However, the transporter proteins themselves have yet to be isolated, or the disappearance of specific amino acids from the hind gut to be proven.
    Finally, let’s compare different feedstuffs in the extent and site of their digestion in the equine. Protein digestibility differs according to both type and amount. It has been repeatedly documented across a wide number of studies that increasing the amount of protein in the diet, also increases the percentage of that protein which will be digested. Perhaps this is due to an adaptation of the digestive system to increase the synthesis of proteolytic enzymes when presented with larger amounts of protein. Total tract digestibility of protein in forages ranges from 73-83% for alfalfa, 57-64% for coastal Bermuda grass hay, and 67-74% for other grass hays. Total tract digestibility for grains or concentrates is much higher, ranging between 80-90%. If however, the site of digestion is take into account, prececal digestion of forages ranges between 25-30% while concentrates are digested much more extensively in the small intestine, up to 70-75%. So what does this mean for the horse owner? Ideally when selecting protein sources for horses, both the digestibility as well as the site of digestion must be considered. Ideally,protein should be digested in the small intestine rather than the hindgut, to optimize amino acid absorption. However, there may be some evidence that this species which does rely so heavily on hind gut fermentation may be capable of some absorption out of the hind gut. The extent of that is yet to be proven.
     
    For next month, we will look at the second piece of protein quality, the amino acid profile of the diet.

  • Horse Math

    Written By Barbara O'Brien

    I have never been very good at math. In fourth grade, when I drew horses all over my work sheets, my math teacher, Mr. Johanson, warned me that I would never learn how to multiply or do long division if I kept it up. I am sorry to say, he was right. I can draw a darn fine horse, but I cannot do long division if my life depended on it.

    That is why it should come as no surprise that I am a master at what, my dear husband, Kevin, calls horse math.

    Horse math is a thought process behind the logic that goes something like this: If I go and see a horse that really should be worth $2000 and the owner is willing to sell it to me for $500, then I essentially have saved the extra $1500 that the horse should have cost. So, when the next horse I want comes along, and is priced at mere $1000, it is a real deal because I saved $500. Doesn’t that make perfect sense to you?

    Kevin says my eyes go all googley and twitchy when I start talking horses. And, I have to admit, he’s right. A while back, I made the mistake of checking out horse ads on the Internet and saw a seven-year-old Morgan Gelding for sale. I recognized the name of his breeder and knew that he was well bred. I looked at his picture and imagined what our lives would be like together. This behavior is not unlike teenage girls who write the name of their intended, over and over again just to see how it looks.

    I contacted the breeder and the delicate process of negotiations began. She sent more photos and patiently answered questions about pedigree, training level, and ground manners. I asked about bad behaviors (there were none) and with each phone call and email the horse sounded better and better. I thought that I better act soon, or she might sell him before I had a chance to see him. Kevin was less than convinced that we had to go and look at him that very weekend, but being the good sport that he is, he agreed to come with me.

    He has a good reason to be wary of my enthusiasm. The last horse that I felt I just had to have, we drove over 400 miles round trip to go see, and it turned out to not only to be blind in one eye, but chronically lame to boot. Now, to be fair to the seller, she may have told me these things, but in my horse lust I may have not heard them.

    We made arrangements with the breeder and headed out on the 150 mile trip to her place. When we arrived, I could see the horse in a paddock by the barn. He was just as described, old style with broad chest, round barrel and good, hard feet. His black bay coat shone in the sun and he stuck his muzzle out to smell me, just as curious about me as I was about him. There was a kindness about him that completely drew me in.

    We brushed him for a while and then we tacked him up. After a few times around the ring and then up and down the driveway, I could see that he had been started correctly and was willing to please. He was everything I wanted in a horse and so we sealed the deal.

    We paid the asking price, (no horse math here), since it was a fair one for such a fine horse and made arrangements to come and get him the next week. He was registered as Redcliff’s Mannington, but I thought Finnian suited him and that is what I named him.

    That was well over 10 years ago and that little Morgan has done it all. He has been shown, I have used him in movies, and he is one of my best photo models. He is still curious and kind, and he is still my favorite.

    Now, because I paid full price for Finn, I had to curb my horse habit for a while and concentrate on the ones I had. That is until a few years later when cruising Dreamhorse, I spotted a Morgan mare for sale across the river. She was old style foundation bred and only 13 years old. Her asking price was ridiculously low and I told Kevin we had better go and see her that evening.

    We drove across the river to Minnesota and pulled into the small hobby farm driveway. I quickly spotted the mare. The owner’s kids were clambering on and off her back while they led her around the yard. Safety concerns aside, I noticed that the mare had the kindest eye I had ever seen and truly loved the children. I began to feel awful that she was even for sale.

    I rode her bareback with just the halter and lead and I could see that this mare had soul and depth and was a keeper.

    We wrote out a check, which according to horse math was about half of what she was worth. I reassured the family that they could visit her anytime they wanted and I just knew that I had done the right thing.

    So, getting back to the horse math:

    It also applies to the number of horses we are feeding. Right now, we have 12 horses. Two are boarders, and ten are our own. Our horses consist of two old quarter horses, two young Half Arabs, four Morgans and two ponies. So whenever I say I have 10 horses, I clarify that it’s really only nine because the two ponies, who don’t eat as much, count as one, right? And Kevin would say that that is horse math at it’s best.

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  • Understanding Horse Nutrition, Part 5: Broodmares and Babies, Oh My

    Written By Dr. Kris Hiney

    Over the last few months we have been discussing exactly how many calories (or megacals for those who are paying attention!) your horse needs to consume, depending on what activities he performs, his personality and what the weather might be doing.

    Broodmares and babies.

    We have yet to discuss an entirely different class of horses, the broodmares and babies. With the breeding season approaching, it is probably appropriate to talk about this special class of horses’ nutritional needs. While this article will focus on their energy requirements, remember, it is especially key for mom and baby to receive the correct amino acids, vitamins and minerals in the diet. These important nutrients are vital for proper growth and development, and ultimately the longevity or usefulness of your new arrival.

    Megacals for Mom - before baby is born.

    Let’s start with our expecting momma. Her energy requirements during her early pregnancy are not actually that much higher than a lightly worked horse. (Refer to Table 1 – ENERGY REQUIREMENTS FOR WORK). She should already be in good body condition if you have done your job of preparing your mare for her upcoming pregnancy (See Part 1 of this series, TOO FAT, TOO THIN, OR JUST RIGHT).

    If you haven’t (shame on you) your goal is to get your mare to a BCS of at least 5 by the time she is at her ninth month of gestation (See CALORIES, KILOCALORIES, MEGACALORIES – HOW MUCH DOES YOUR HORSE NEED? for more information on increasing your horse’s body condition score). Otherwise, you want to ensure that your mare maintains that healthy BCS of around 5.5 -6.

    Essentially the mare in early and mid gestation has lower energy requirements than a horse in light work, making her fairly easy to feed. You can usually support her increased energy needs by simply increasing the quantity of good quality hay. However, during the last trimester of pregnancy, her fetus is growing rapidly, which drives up her energy requirements to fall between horses in light and moderate work.

    Table 4. Energy Requirements (Mcal/d) for Pregnant and Lactating Mares. 
    Activity Time – tracking weight increase.

    If you like being a very hands on horse owner (again – great youth project!), you can also track your mare’s increase in weight that is healthy for her and her foal. Using your weight tape (or string), check your mare’s increase in weight over her pregnancy. Overall, she should gain between 12-14% of her non-pregnant weight. She should gain around 5, 7, 10 and 13% of her original weight in her 8th, 9th, 10th and 11th month of gestation respectively. See Table 5 for a handy reference.

    Table 5. The Expected Weight of Mares During Late Gestation by Month Compared to the Mare's Original Non-pregnant Weight. 
    Megacals for Mom - after baby arrives!

    But look what happens after baby arrives! The new momma actually has quite the job to do in producing milk for her rapidly growing offspring. Her energy requirements have now increased by over 50% of what she needed during gestation. Compared to our working horses, your mare now almost reaches the energy needs of a racehorse of the similar size! Many horsemen often forget how demanding a job milk production truly is for your broodmare. Typically it is most effective to supplement your mare’s diet with a concentrate that is already specifically formulated for broodmares. Consult your local equine feed store or horse nutritionist for advice. This will allow her to meet her increased needs for other nutrients as well. While the broodmare definitely needs the extra calories, it is equally important that the diet is balanced to meet her protein, mineral and vitamin requirements to support lactation, and thus foal growth.

    Feeding tips.

    In order to provide a rough estimate of the amount of feed you will need for your mare, let’s work through a typical feeding strategy for a mare. We will work with a 1000 lb mare for simplicities sake. Now for both health and behavioral reasons, I encourage owners to always feed horses 2% of their horse’s body weight in hay or forage per day. We will actually visit the logic in feeding strategies in an entire article coming soon. For this mare, that means she should be eating 20 lbs of hay per day. I like to feed the pregnant mares and lactating mares a good quality alfalfa hay, in part to help meet their protein needs, as well as an increased need for calcium. Let’s use alfalfa hay which has a caloric density of 0.93 Mcal/lb fed. If we multiply the caloric content of the hay by the lbs eaten we reach her total caloric intake. 0.93 Mcal/lb * 20 lbs = 18.5 Mcal

    Comparing our value here with Table 4 above shows us that the mare can consume enough hay to meet her energy needs. She just doesn’t need to consume that many additional calories. However, I would still recommend supplementing her with a ration designed for broodmares. Her energy intake is, of course, dependent on the mare consuming all the hay she is offered. Does she refuse to eat some of her hay and is therefore wasting it? Do you offer her hay free choice? If the hay is of high quality and is palatable to the mare, typically she will volunteer to eat more than 2% of her body weight per day. Also, remember the best indicator of caloric needs of the mare is her BCS. Keep an eye on her condition when changing feed intake.

    Feeding when baby is here!

    Now let’s compare our girl while pregnant to when she is lactating. Again, we will feed her the same amount of hay, so that she consumes 18.5 Mcal/d. However, during her peak lactation, she is now 10.4 Mcal short! What are our management strategies now? One easy strategy is simply to allow the mare to consume as much forage as she wants. These girls will often increase the amount of hay they eat per day in order to support their lactation demands. However, as mentioned before, we usually supplement these girls with a broodmare concentrate. Let’s use a grain mix with a calorie content of 1.3 Mcal/lb. (I’m using the energy value of a typical commercial feed designed for broodmares). To determine how many lbs of grain we would feed, divide the amount of calories needed by the calorie concentration of the feed. 10.4 Mcal needed/1.3 Mcal lb = 8 lbs of grain Ideally you would split her grain into two equal feedings per day. Now, while this is a fictitious scenario, most alfalfa hays and typical horse feeds will be similar in their caloric content. Read your feed tag for specific information on the feed you select.

    Minerals of Note: 

    While this month’s article is truly based on the energy needs of our ladies, I would feel remiss to not mention calcium (Ca) and phosphorus (P) when talking about broodmares. It is essential for proper bone development that these two key minerals are not overlooked. Not only do we need to feed adequate amounts of Ca and P, but they must be fed in the proper ratio. Ideally we want to see the ratio of Ca to P in the diet at approximately two parts Ca for every one part P, or 2:1. However, anywhere between 1:1 and 6:1 is acceptable. What you don’t want to see is the amount of Ca to extend beyond 6 parts or for your ratio to become inverted. In that case, you would have more P than you have Ca. Not sure how to figure it out? Let’s assume she is getting 105 g of Ca and 23 g of P from her hay. We would divide the g of Ca by the g of P, or 105/23 = 4.6. The ratio of Ca to P in this scenario is 4.6:1 which is acceptable. However, our girl will be short on P if she is receiving no additional mineral supplement.

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