Grains and other plants are processed to produce many different products for human consumption, including flour, cooking oils, syrup, sugar, and alcoholic beverages. The parts of the grain or plant that remains after processing are by-products. For many horse owners, the term by-products makes them think of lower quality but that is often not the case at all.
Many by-products contain nutrient levels or attributes that make them better feed ingredients for horses than the initial grain or the primary end product of the processing. There is a long list of by-products that may be safely used in horse diets, but their nutritional value varies. You may be surprised at some of the products that are considered by-products.
The sugar industry produces two of the most popular by-products in horse diets, molasses and beet pulp. Molasses has been used for years because horses love the taste and molasses helps prevent settling out or sorting of ingredients in mixed feeds. Although molasses is certainly sweet tasting, at typical inclusion rates of 10% or less in most sweet feeds, molasses actually contributes less than 5% sugar to a ration. Beet pulp is the fiberous portion of the sugar beet that remains when the sugars have been extracted to make sugar. Plain, dried beet pulp is very low in sugar content. However, beet pulp is very dry and often molasses is applied on the shreds of beet pulp being sold for animal feed so when low sugar is desired, look for non-molassed beet pulp. Beet pulp provides highly digestible fibers and a greater water holding capacity than hay or other fiber sources. It provides low starch and sugar calories, more calories than afalfa, and fermentable fibers to help maintain hindgut health in horses. Beet pulp is often fed soaked to help increase water intake as well. Furthermore, beet pulp is low in protein. amino acid balance and many minerals. If used in a diet, beet pulp should be blended with other ingredients to provide adequate nutrition balance.
The flour industry also produces popular by-products used in horse rations. Wheat bran, which is part of the wheat that remains when the flour is removed from the grain, has been used by horse owners for many years to add bulk and fiber to a grain mix. Wheat bran mashes have been thought to help prevent impaction colic although the research indicates the added water may have been providing much of the benefit. Wheat middlings (midds) are also a by-product of flour milling. Wheat midds are the bran and the germ of the grain, the healthy parts that people are trying to get back into their diets by eating more whole grains. Since the starchy flour has been removed, midds are lower in calories and starch but higher in fiber and protein than the original wheat grain, making them a more valuable feed ingredient in many ways than the wheat grain would be. Both wheat midds and wheat bran are very high in phosphorus and low in calcium, so they must be blended with other ingredients and balanced with adequate calcium to provide a proper calcium to phosphorus ratio in the finished ration.
Rice bran is a by-product of the rice milling industry. Similar to wheat midds, rice bran contains the bran and the germ of the rice grain that is removed to make white rice. Rice bran is higher in fat content than wheat midds, which makes rice bran higher in calories but also requires stabilization or it turns rancid very quickly. Also, similar to wheat bran and midds, rice bran is naturally very high in phosphorus and low in calcium which must be taken into consideration when balancing the total diet.
The process of extracting soy oil from soybeans produces two by-products used in horse feeds, soybean meal and soy hulls. Soybean meal is low in fat, since it is what remains of the beans when the oil has been extracted, but it is high in protein and provides an exceptional amino acid balance for horses. This makes soybean meal the protein source of choice for high quality horse feeds. Soy hulls are the external layer of the soybeans and provide very digestible fiber and low starch calories, similar to beet pulp.
Purina utilizes by-products in many of our horse feeds but they all must meet very high quality standards and testing, as do all Purina ingredients. By-products can be variable in quality and nutritional content, so we do have very strict standards that these ingredients must meet. When the quality standards are met and the by-products are blended in proper amounts with other quality ingredients to provide balanced nutrition, by-products can contribute to an excellent diet for horses.
About the Author
Dr. Karen Davison is an Equine Nutritionist and Sales Support Manager for the horse business group at Purina Animal Nutrition. Her expertise includes equine nutrition, reproduction, growth and exercise physiology. She received her M.S. and Ph.D. from Texas A&M University.