Formulating Horse Feeds - Different Formulation Strategies Produce Different Results

Karen E. Davison, Ph.D.
Manager- Equine Technical Services
Land O’Lakes Purina Feed



When choosing a horse feed, looking at the guaranteed analysis can help you determine if the nutritional content of that feed is appropriate for the age and activity level of your horse. You would think that two products that both contain 14% protein, 6% fat, etc. would be pretty much the same feed. However, products with similar guaranteed analysis may be manufactured using very different formulation strategies and have very different formulas. This can affect the nutritional value for your horse. The most common formulation strategies are “Least-cost” formulas and “Fixed” or “Locked” formulas. Both of these strategies have benefits and draw backs. There is a third strategy that Purina uses for premium horse feeds, “Constant Nutrition” formulas, which is more nutritionally accurate than either of the other strategies.

Least-cost formulas allow a manufacturer to adjust the ingredients in the formula based on cost of those ingredients. As long as the formula still meets the guaranteed analysis, the manufacturer can change the ingredients used in the formula. In some circumstances, the change in ingredients doesn’t change the effectiveness of the diet so it makes sense to meet the nutritional needs of the animal in the least expensive way. There would be no benefit to making a more expensive ration to achieve the same results. For instance, if you are feeding cattle and being paid for weight gain and a least-cost formula will not change the rate of gain or feed efficiency of the cattle, but will be less expensive to feed, that just makes good business sense. However, in some cases, especially when feeding horses, a major change in ingredients can dramatically alter the effectiveness of the diet, even when the nutrient levels don’t change. A good example of this would be substituting cottonseed meal for soybean meal in a diet for growing horses. Soybean meal and cottonseed meal may both have similar total protein content and could be interchangeable in a formula to meet the protein guarantee. However, cottonseed meal does not provide the same quality of protein to support growth as soybean meal and young horses will not grow as well eating a feed with cottonseed meal as the protein source. So, in this case, the least-cost formula may be less expensive per ton but the loss in animal performance will negate any cost savings. In addition to potential for reduced performance, there is always the potential for reduced palatability or digestive upset in horses when large shifts in ingredients can occur in their feed.

With a fixed or locked formula the same ingredients and amounts of ingredients are used every time the feed is made, regardless of price or nutritional variation of those ingredients. This sounds like the most consistent way to make horse feed however, there is a draw back. All ingredients, even very good quality ingredients, have some variation in nutritional content. All oats will not have the same protein or mineral content. If the formula is completely locked and not taking into account the nutritional content of the individual ingredients, the level of nutrition provided in the finished product can vary. Horses do benefit from consistency in their diet but they don’t have a specific requirement for certain ingredients. The purpose of ingredients is to provide nutrients the horse needs. So, while a fixed formula does provide the same amount of ingredient in every bag, it may not provide the same level of nutrition. For example, a horse feed made of 49% oats, 20% beet pulp, 16% corn, 8% alfalfa and 7% soybean meal would average 14% protein, using the average book values for these ingredients. However, with the typical range in protein content of these ingredients, the end product could range from 12.4% to 21.1% protein. Other nutrient levels will vary as well. So, while a fixed formula does insure a consistent ingredient profile, it may not provide the most consistent level of nutrition for the horse.

“Constant Nutrition” formulation is a key part of the Purina FeedGuard™ Nutrition System. This strategy provides consistent, reliable nutrition in every bag of premium Purina horse feed. Under the Purina FeedGuard™ Nutrition System, stringent quality standards are set for ingredients which are purchased only from an approved list of suppliers that meet those strict criteria. Then, when ingredients arrive at a manufacturing facility, the ingredients are inspected, sampled and analyzed for nutrient levels. This is more accurate than using published book values or supplier averages for nutrient levels of ingredients. If an ingredient is approved, then the tested nutritional content is entered into the formulation system, which makes small adjustments in amounts of ingredients to maintain a consistent nutrient level in the finished product. There are strict restrictions for how much adjustment is allowed to ensure consistency in formulation. For example, the amount of soybean meal may be adjusted slightly to compensate for a lower protein in another ingredient, but cottonseed meal couldn’t be substituted for soybean meal. This formulation strategy ensures that horses receive the most consistent nutrition possible.

Forage for Horses

By J. Kathleen Young, Ph.D

Why should horse owners be concerned about forages for their horses? Horses need to be fed at least one percent of their body weight daily (dry matter) as forage. Most horses are fed more than that; many receive two or more percent of their body weight per day in grass or hay. This means that a 1000 pound horse may easily eat 15-20 pounds per day of hay, along with 3-6 pounds of a grain ration. When problems occur that may relate back to nutrition, people usually look at the grain ration. However, when the vast majority of the horse’s diet is hay or grass, we must pay more attention to the important nutritional role that the forage plays in the horse’s nutritional status.

Quality of Forages

There are several factors that affect the quality of hay, therefore the nutrient content. The higher the quality of the hay, the better the horse’s digestive tract is able to digest and absorb the nutrients contained in the hay.
The factors that affect the quality of the hay include plant species, fertilization, maturity at time of harvest, season at which hay is harvested, climate conditions, storage conditions, and age (time since cutting). The maturity of the plant at time of harvest determines the hay quality more than any other factor. Young, leafy, immature plants contain more protein, energy and minerals than older, stemmier plants. As a plant matures, it contains more indigestible fiber (lignin), therefore is less digestible for the horse, as well as containing less protein, energy and minerals. To ensure high quality hay, plants should be harvested at the proper stage of maturity, for instance, timothy should be cut in the pre-bloom or early-bloom stages for the highest nutrient content.

Plant species (e.g. grass vs. legume) has an impact on the nutrient content of the hay, but not as much as most horse owners believe. The maturity of the plant when it was cut has much more influence. Alfalfa tends to have more protein, energy and calcium than grass hays, but research has shown that a good quality grass hay may provide more nutrients than a medium or low quality alfalfa because the higher quality grass hay is more digestible (less fibrous). For example, for protein to be of value to a horse as amino acids, it must be digested and absorbed (as amino acids) in the horse’s upper gut (stomach and small intestine). Since the fiber in hay can only be digested by microbes in the horse’s hind gut, the more fiber in the hay, the more that hay is digested in the hind gut. In one study, when horses were fed medium quality alfalfa hay, only 2% of the protein was digested in the upper gut. This means that 98% of the protein was of no benefit as amino acids to the horses. Horse owners sometimes feel that alfalfa is always a better choice for horses than grass hays, but that is not necessarily true. Further, high quality alfalfa may not provide enough fiber to maintain a healthy hind gut in the horse. A certain amount of indigestible fiber (bulk) is necessary to ensure the health of the microbes in the hind gut, as well as helping to maintain proper motility in the hind gut.

Fertilization primarily affects yield per acre rather than nutrition of any one bale of hay. The season at which the hay is harvested affects quality in that digestibility is highest for forages harvested in the spring, somewhat lower in mid to late summer, and then it rises slightly in autumn. Climate conditions, such as excessive moisture or drought can affect the quality of hay, especially since climate conditions can affect when the hay is cut. Often the plants become more mature than optimum because climate conditions are not conducive to harvesting at the best time.

Storage conditions and age (time since cutting) primarily affect vitamin content of hays. Many vitamins are not very stable over time and lose biological activity. Environmental conditions such as heat, sunlight and rain can hasten the loss of vitamin activity in hay.
Characteristics to look for in choosing high quality hay include:
· High leaf to stem ratio (indicates less mature plants)
· Small diameter stems (less mature plants)
· Fresh smell and appearance
· Cleanliness
· Color (faded, yellow or brown color may indicate aged hay or poor storage conditions)
· Few seed head or blooms (less mature plants)
Hay analysis may provide more information, but the results need to be interpreted with caution. For instance, the crude protein determined by analysis does not indicate the site of digestion in the horse. A hay that tests high in crude protein and also high in acid detergent fiber (ADF) is not well digested in the horse’s upper gut, thus the amino acids from the protein are not readily available for absorption in the upper gut. A hay with lower crude protein and lower ADF may actually provide more nutrients, including protein, energy and minerals to the horse.