Fun With Feed Math! Part 4: Using Feed Tags

 Written By Dr. Kris Hiney

We have talked about what information should be included on a feed tag, regardless of type of feed. In this article we will put that information into use to aid you in selecting the best (and perhaps most economical) feed for you to use. So let’s start with what the guaranteed analysis means to you.

Crude Protein- The amount of protein in horse feed is often the most talked about, but most misunderstood component of horse feed. Owners often select their horse feed solely on the percent protein with little consideration to other vital components of the diet. While protein is important, it is certainly not the only criteria by which you should select your feed. Horses need the amino acids contained in protein for maintenance as well as synthesis of body tissues such as muscle, bone, organs etc, as well as synthesis of hormones and enzymes necessary for body function. Horses which need more protein in the diet are those that are busy synthesizing more tissue such as growing horses, broodmares and lactating mares. Horses that are mature and not at work (our maintenance horses) will require the least amount of protein. For example, a 1100 lb maintenance horse will require between 540 g and 720 g of crude protein in the diet per day. The range in those numbers are due to differences in temperament (more or less active horses), environment etc. Using your feed tag, you can determine how much protein your horse is receiving. Let’s assume you selected a feed that contains 12% crude protein and you feed 4.5 kg or 10 lbs of feed (to learn to convert to lbs see below). Multiply the percent protein by the amount fed to determine the amount of protein provided.12% or 0.12 x 4.5 kg = 0.54 kg.12% or .12 x 10 lbs = 1.2 lbsYour horse is thus consuming 0.54 kg or 540 g of protein by eating that amount of feed. Now, don’t forget, the horse will also be receiving protein from the forage in his diet as well. Now compare that to the horse’s protein requirements. For a maintenance horse, he has already almost met his requirement even before we consider his hay! To determine where your horse fits in the chart, see Energy Requirements for the Working Class. Then use Table 1 below to find his protein requirements.

Table 1. Crude protein requirements in grams for horses of varying work intensities. These numbers are derived from the National Research Council, Nutrient Requirements of Horses. 2007 edition.
Work Intensity
Wt of horse (lbs.) Maintenance Light Moderate Intense
900 515 572 628 705
1000 573 636 699 784
1100 630 699 768 862
1200 687 762 837 939


Most equine feeds will contain protein in a range of 8-16% of crude protein, with those higher in protein designed for the young growing horses or broodmares. Some feeds might be higher in protein, if they are designed to be a protein supplement, versus a typical concentrate fed for energy.

Math Time

Pounds versus kilograms. Many horse owners are often frustrated by the different units provided by feed tags, nutritionists, books etc. In our protein example I have provided the horses requirements in grams. However, most individuals in the United States think in pounds. So let’s learn how to convert back and forth shall we! To convert grams to pounds, remember that there are 1000 grams in every kilogram. So using my numbers above I would take 540g and divide by 1000 to convert to kg. Therefore, my maintenance horse needs between 0.540 kg and 0.720 kg of protein per day. Now, changing from lbs to kilograms is fairly easy. One kilogram is equivalent to 2.24 lbs. Many times we will round down to 2.2 lbs/kg for simplicities sake. Now let’s convert our numbers from above.

.540 kg x 2.2 lbs/kg = 1.2 lbs.

.720 kg x 2.2 lbs/kg = 1.6 lbs.

To covert lbs to kg, you simply do the opposite, and instead of multiplying, you would divide by 2.2. If I had 5lbs of feed, and wanted to convert it to kg, I would use the following equation: 5 lbs ÷ 2.2 lbs/kg = 2.3 kg. Remember, numerically, the amount in kgs will always be less than it is in lbs. For example, an 1100 lb horse is equivalent to a 500 kg horse.

Crude Fat -Those horse owners looking for more bang for the buck should pay attention to the crude fat in their horse feed. Addition of supplemental fat to a feed greatly increases the amount of calories in a feed. This is important as fat is a very efficient and safe way to add energy to a horse’s diet compared to adding traditional grains, such as corn and oats. Horses do quite well at digesting fat, and as long as it is not fed in excessive amounts (over 20% of the diet), find it tasty as well. Typically, a non-fat added feed will contain less than 4% fat, with those feeds with additional fat containing between 6 and 15% fat. But what about Omega Horseshine®, which last month I showed you contained 30% fat? Well, that is because Horseshine® is not a traditional concentrate but rather a specific fat supplement. As its primary ingredient is flax seed (37-40% fat), we would expect that this product would be much higher in overall percent fat. Be sure to refer to back to Equine Energy Requirements to decide if your horse would benefit from a fat added feed.
Crude Fiber- Crude fiber is often used to reflect the amount of energy in a horse feed. Typically, fibers will contribute less energy to a horse’s diet than do low fiber feeds such as grains. Low fiber feeds usually will then contain more soluble carbohydrates and thus energy. For example, corn is typically 10% fiber and has 3.9 Mcal/kg while grass hays can range between 50 and 70% fiber and will contain between 2 and 2.3 Mcal/kg (all numbers are expressed on a dry matter basis). Thus there is typically an inverse relationship between fiber and energy content. Even between typical grains fed to horses we can have a significant variation between fiber content. Let’s compare oats versus corn. Oats, which are often thought of as a safer feed for horses, typically contain between 30 and 40% fiber due to the presence of the hull, and thus contribute only 3.2 – 3.3 Mcal/kg to the horse.
Fiber and the 21st Century Previously it was quite easy to predict the energy content of concentrate feeds for horses based on the fiber content. This relationship still exists, provided the feed contains less than 12% crude fiber. However, many equine feeds are now formulated to contain much more fiber, as researchers have discovered many downsides to feeding high starch diets to horses. Higher fiber feeds usually also have the addition of fat, which offsets the lowering of caloric content by choosing less nutrient dense feeds. Horse feeds that contain beet pulp, alfalfa meal, soybean hulls etc will often be higher in fiber, but coupled with rice bran or flaxseed for the added fat boost of energy.
Calcium and Phosphorous -We will discuss these two very important minerals together. The amount of calcium and phosphorous in the diet is absolutely critical for growing horses and broodmares. These animals are rapidly forming bone which will be crucial for a sound, productive life. Imbalances of these nutrients in your broodmare’s or foal’s diet can cause permanent changes in bone and cartilage which can lead to painful developmental problems in the future. Expect that feeds designed for these classes of horses will be higher in calcium and phosphorous than those designed for maintenance horses. We discussed previously in our article, Broodmares and Babies, the idea of the all important calcium to phosphorous ratio. Remember, you should never have more phosphorous in the diet than you have calcium. At a minimum, you should have a 1:1 ratio between calcium and phosphorous, with a ratio of 2:1 in favor of calcium more ideal. However, I can’t stress this enough, remember, that your horse’s diet does not exist solely of the feed you choose, but also the forage! Always try to select your horses’ concentrate with consideration of not only it’s class, but also what you base the horse’s diet on –it’s hay!
Copper- Copper is an important mineral needed by horses for the function of many key enzymes. It plays an important role in the formation of collagen, and thus is critical for proper joint development in young horses. Copper also aids in iron metabolism as well as the elimination of free radicals in the body. However, it is needed in much smaller amounts than Ca and P, and thus is referred to as a micro-mineral. Its concentration in your feed will be listed in the units ppm or parts per million. An equivalent way to think of Cu concentration would also be mg/kg, as there are 1 million milligrams in every kilogram. Let’s use Horseshine® once again. Looking at the label, we can see it contains 116 ppm Cu. If you fed one half pound of this supplement per day (or 0.5 lbs ÷ 2.2 lbs/kg = 0.227 kg) your horse would be receiving 0.277 kg of Horseshine®. To determine the amount of Cu the horse is eating, multiply the amount fed by the concentration in the feed, just like we did for protein.0.277 kg x 116 mg/kg = 26 mg of copperTherefore, Horsehine® is adding 26 mg of copper to your horse’s diet per day.
Zinc -Zinc, like copper, is considered a micro-mineral, and is also listed in parts per million on the feed tag. It plays a similar role in aiding in enzyme function, but in such a wide array in the body as to be too numerous and diverse to mention. It is frequently added to commercial equine feeds due to the variability in hays and forage. Using our same serving of Horseshine, zinc is listed at 321 ppm. Thus, the horse gets 89 mg of Zn with every serving (0.227 kg x 321mg/kg = 89 mg).
Selenium -Selenium is often one of the most commonly discussed minerals is horse nutrition, mainly due to its essential function in the immune system and role as an anti-oxidant, but also due to its tremendous variability in feeds across the country. In the United States, some regions are considered selenium rich and some selenium deficient. Thus forages or hays produced in different areas can vary from selenium deficient to even reaching toxic levels of selenium. Even weather conditions can cause alterations in Se content of feed, as drought conditions can greatly increase selenium uptake by plants. Overall, selenium may certainly be needed to be supplemented in the equine diet, but in much lower concentrations than even Cu or Zn. Most feeds will vary in the range of 0.1 to 0.5 ppm of selenium in order to meet the horses’ requirements, but to avoid any toxicity issues.
Vitamin A- Vitamin A is needed by the horse in much larger quantities compared to other vitamins. Horses consuming green forages (grazing horses) typically meet their needs quite easily. However, horses which consume a primarily harvested forage diet (hay) might have a possibility of becoming deficient, especially if the hay has been stored for a great length of time. The vitamin A content of hay does decrease over time, with a large percent of all vitamin A lost over one year’s storage of hay. Thus, most commercial feeds are supplemented to ensure adequate intake by the horse.


 

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