Tag Archives: Dr. Kristina Hiney

  • Minimizing the Stress of Weaning

    Written By Dr. Kris Hiney

    The fall season is here and with it often comes the time for weaning our foals. Many successful weaning strategies exist but it is important for the manager to choose the optimal one for their facilities and management style. These decisions are important and can affect the growth, well being and even the future behavior of your foal.
    When is it appropriate to wean?
    Foals can be weaned at any age provided their proper nutrition and socialization skills are ensured. Foals whose dam’s may die at birth are obviously “weaned” from their dam at an extremely young age. While it is preferable to find a willing nurse mare, and it is even possible to induce lactation in a non-pregnant mare, many owners choose to put the foal on a liquid diet of formula designed to match the mare’s own milk.  Specialized milk replacer, goat’s milk and supplemented cow’s milk can all be used successfully.  Prior to doing so, it is important to ensure that the foal has received adequate amounts of high quality colostrum, as the proteins found in the milk replacer may block the later absorption of immunoglobins from colostrum. Colostrum content quickly decreases in post-partum mares and should have been harvested within the first three hours post parturition of the donor mare.
    Orphaned foals must be fed frequently , initially from a bottle, but can then be taught to drink from a pail, similar to calves. Initially the foal should be fed at 5-10% of its body weight in the first day, and then increase to 20-25% of its body weight by day 10. Solid feeds can be introduced early, as the foal would typically begin to ingest feed in imitation of its dam after only one week of being born. Milk replacer pellets are available, and can help supplement the foals’ initial liquid diet.   Foals can be weaned from this liquid diet by 10-12 weeks of age. Most importantly, some sort of companion should be found for the foal. Often orphan foals develop undesirable behaviors as they have no guidance from a mature horse as to what constitutes appropriate social behavior. Typically, orphaned foals view humans as their peers, which may result in some rather inappropriate rough play!
    With the exception of extremely early loss of the dam for a variety of reasons (death, injury, sales, etc.) most managers choose to wean foals between three and six months of age. In the feral state, foals typically are self weaned by 35 weeks of age or between eight and nine months. At five months all foals spend 50-70% of their day consuming solid feed, compared to about 2% of the day suckling. Mare’s milk production also begins to drop off by three months of age, at which time foals are consuming a high percentage of natural feeds through grazing, hay or concentrates.  It is advantageous to introduce the foal to the feeds it will be consuming post-weaning to ensure an easier and more stress-free transition. This will also help prevent fluctuations in growth rates that may place the foal at risk for developing developmental disorders.
    After insuring that the proper diet is being fed (see previously related articles concerning protein, energy and minerals for growth), the management system used is important to consider. Foals weaned in isolation (such as confined in a box stall) show more incidences of stereotypies (such as weaving, cribbing and wood chewing) and are more vigilant (less time standing relaxed) than foals weaned in pairs. Foals weaned in stalls also show more abnormal behaviors such as stall licking, kicking, rearing and pawing than weanlings weaned in a paddock. Even horses stabled for the first time as two year olds exhibited much less aberrant behavior and were more relaxed when stalled in pairs versus singularly.
    Therefore the ideal management system would wean the foals with a counter-part, rather than in isolation. For example, at our facility we wean the foals by removing the dams, with foals remaining in the same pasture and with the same herd mates with which they have been raised. This results in very little stress (at least as exhibited by vocalizations and seeking of their dam) which is frequently resolved within two days post weaning.   Even in this system we wean in pairs, whether or not this actually relieves stress for the weanling. If raising only one foal, it is advisable to seek out an older quiet pasture mate, or even to find another youngster to raise with it. Many horse owners find themselves in a similar situation and may be willing to board another weanling or send theirs as a companion.
    Alternative strategies include gradual weaning, in which the mare and foal are separated, but are allowed all behaviors except nursing. Typically this is done over a fence that the foal simply cannot nurse through. After one week, the mare is removed completely. Foals weaned in this manner, exhibit less stress and have lower levels of cortisol (a stress hormone) than foals which are weaned abruptly. However, these foals are no different than abruptly-weaned foals after two weeks. The advantages to this system may simply be a lessened possibility for injury or disease.
    Weaning stress may also make the foal more susceptible to diseases. Because of this, be sure that the foal is in good health prior to weaning (we typically have vaccinated the foal and ensured a high immune status prior to weaning) and there are no undo stressors. For instance, plan the time of weaning for when the climate is not too adverse (either too hot or too cold/wet).   Because the mare and foal may show high stress and try to re-unite, check that the facilities used for weaning are extremely safe. Expect that maiden or younger mares may exhibit a longer period of time in which they still call for or seek out their foals. Halter breaking is not advisable right at the time of weaning either, as the foal is already stressed and more reactive. Ideally foals are handled from birth, which can lessen the stress of procedures often introduced at this time (vaccinations, deworming, farrier care, etc).
    Care of the mare is simple, with usually a decrease in ration quality or quantity from that received as a lactating mare. Although her udder will fill initially, it is important to not milk the mare, as this will only further stimulate lactation. The udder should become soft within a week of weaning.   She can then be returned to her pre-foal life, whether that is as a riding horse, a gestating mare, or simply a mare of leisure.

    By thinking through the weaning system and the safety and nutritional needs of both mare and foal, the stress of “growing up” for the foal can be greatly minimized.

  • Lipid Nutrition: Part 4, Omega-3 Fatty Acids

    Written By Dr. Kris Hiney
    In previous articles we have discussed the many benefits of feeding fats to horses. Typically these fats in feeds are vegetable oils, or even occasionally animal fats. We have not yet discussed specifically the type of fat in the diet. However, researchers in human and animal medicine have much information supporting the idea that specific types of fatty acids can provide numerous health benefits. This month we look at the science behind Omega-3 fatty acids and begin the process of understanding the terminology used.
    Omega-3 fatty acids
    So what makes Omega-3 (or “n-3”) fatty acids so unique? Quite simply, it’s just the location of the double bonds which occur between the carbons in the fatty acid chain. The location of these bonds are what provide these fatty acids with their naming system.  Omega-3 fatty acids have the last double bond placed three carbons from the methyl end of the carbon chain, which is the opposite end from the attachment to the glycerol backbone in a triglyceride. Compare this to the Omega-6 fatty acids (or “n-6”), which have their last double bond six carbons in from the methyl end. This simple change in location of a double bond can have tremendous impact on the metabolism of these fats in the body.
    Essential fatty acids
    Previously we mentioned that horses must ingest certain fatty acids in their diet as they do not have the capability of synthesizing them in great enough quantities. These include linoleic acid and linolenic acid. Both of these fatty acids are 18 carbons long but differ in the number and placement of the double bonds.  Linolenic acid has three double bonds with the last one placed three carbons from the methyl end.  Thus, it is an Omega-3 fatty acid.  Linoleic acid has two double bonds, with the last double bond six carbons from the methyl end and is an Omega-6 fatty acid. These two fatty acids represent the essential fatty acids that horses must consume. These fatty acids do occur in forages and concentrates such as corn and oats, just in smaller quantities than we think about in more fat rich feedstuffs. Typically there will be more Omega-3 fatty acids in forages, especially pasture grasses, while grains will contain more Omega-6 fatty acids.
                  Linoleic Acid Molecular Diagram               Linolenic Acid Molecular Diagram
    The horse, as well as humans, must consume these fatty acids as we both lack the necessary enzymes to build these structures on our own. However, we do possess the enzymes needed to elongate these fatty acids to more complex fatty acid structures.  These elongation enzymes are shared by both linoleic and linolenic acid in their metabolic pathway. Their products in turn can be used to synthesize a whole host of biologically active compounds.  Linolenic acid can be elongated to eicosapentanoic acid or EPA, a twenty carbon fatty acid with five double bonds, and docosahexaenoic acid or DHA, a 22 carbon fatty acid with 6 double bonds, as well as others. Both EPA and DHA are Omega-3 fatty acids, due to their origin from an Omega-3 fatty acid. Linoleic acid is elongated to arachidonic acid, a twenty carbon fatty acid chain with four double bonds which is, of course, an n-6 fatty acid.   These fatty acids can be used to synthesize eicosanoids, which are biologically active lipids.
    Eicosanoids have hormone-like activity which is typically mediated locally within a tissue. These include prostaglandins, thromboxanes and leukotrienes.   These compounds differ by their structure and perform a host of activities within the body. All of these compounds are necessary for normal bodily function, but an imbalance can contribute to a disease state. Prostaglandins can effect smooth muscle contraction, vasodilation, inflammation, pain, and fever, as well as gastric acid and mucus secretion. Leukotrienes are released during the inflammatory process and can contribute to inflammation and bronchoconstriction. While their role may be to aid in healing the damaged tissue, overproduction of leukotrienes can contribute to asthma or allergic reactions. Finally, thromboxanes cause the aggregation of platelets and constriction of blood vessels. Again, all of these compounds are part of normal bodily function, but their potent effects can contribute to the diseased state.
    So how do Omega-3 fatty acids fit into this story of thromboxanes and leukotrienes? When animals ingest greater quantities of Omega-3 fatty acids, these fatty acids can displace arachadonic acid in the cell membrane. Thus, there is less arachadonic acid available to be released and formed into eicosanoids.   Increased linolenic acid also decreases the amount of linoleic acid which is elongated simply due to a competition for the same enzymes. The elongation products of linolenic acid and subsequently EPA may also directly counter act some of the inflammatory products of arachadonic acid metabolism. Thus increased consumption of Omega-3 fatty acids may aid in decreasing inflammation in the diseased state.
    Feeding Omega-3 fatty acids may be helpful for horses which may have chronic pain or inflammation. Traditionally horsemen have used NSAIDS, or Non-Steroidal Anti-Inflammatory DrugS, to manage pain and inflammation. When we provide NSAIDS these compounds act by blocking the activity of enzymes which cause the release of inflammatory agents.  However, NSAIDS are not specific and block the activity of both cox-1 and cox-2. These enzymes are essential in the conversion of arachidonic acid to progstaglandins.  Cyclo-oxygenase 1 unfortunately is also intimately involved with the formation of thromboxane in platelets and in gastromucosal integrity. It is the inhibition of cox-1 which leads to the formation of ulcers in horses which have long term NSAID administration. However, many specific cox-2 inhibitors have been produced (Celebrex® and Vioxx®).
    Sources of Omega-3s for horses
    Compared to humans, it may be harder to increase the consumption of Omega-3 fatty acids in horses, but not impossible. Typically the greatest concentration of Omega-3 fatty acids is found in marine fish. Certainly fish oils have been fed to horses, but there may be limits in the acceptability of fish oil by the horse. Flaxseed, however, is also an excellent source of Omega-3 fatty acids, has a slightly sweet, nutty, whole-grain flavor and aroma, and is readily accepted by horses. Many flax products are now offered to the horse owner.  Increasing consumption of fresh grass will also boost the Omega-3s in your horses’ diet.
    Next month we continue to look at Omega-3 fatty acids in the horse’s diet and examine some of the available literature concerning their effects in the horse.

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