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Factors Affecting Forage Intake and Utilization by Horses
Department of Animal and Food Sciences
Kentucky foals marketed as weanlings and yearlings at public auction annually produce revenue in excess of $300 million. Most of these horses will be raised in forage-based nutritional programs. While forage is an important nutrient source it can not provide all of the nutrients needed by broodmares and growing horses. The amount of supplementation needed will depend upon the nutrient composition of the forage and the amount of forage consumed by the horses.
It is a simple matter to assess nutrient composition of forage but there are few validated methods of predicting the amount of forage any particular horse will consume in a day. Factors that have been examined in other species (such as cattle and sheep) include chemical composition of the forage and stage of maturity of the forage. Because horses and cattle have different types of digestive systems, the information that has been gathered in cattle can not be applied to horses.
The purpose of this project is to investigate the factors that alter (increase or decrease) the amount of forage consumed by horses. Once these factors are understood, equations for predicting the amount of forage consumed by grazing horses can be developed. These experiments will enhance our ability to design effective and efficient nutritional programs for broodmares and growing horses.
2010 Project Description
Experiments were completed that compared forage intake by pregnant mares and non pregnant mares and in lactating and nonlactating mares. In the first experiment, 12 pregnant and 12 nonpregnant mares were used. In the second experiment six lactating and six nonlactating mares were used. In both experiments mares were initially adapted to forage based diet for at least 7 days and then forage intake was measured for 10 days. Forage samples were assayed to determine neutral detergent fiber and acid detergent fiber consumption.
Two separate experiments was conducted to evaluate the acceptability and intake of teff hay (Eragrostis tef) to horses. Teff is a summer annual grass that has become more available in the US. The acceptability of teff was compared to alfalfa and timothy hay using two choice preference tests. In a second experiment total intake of teff hay was compared to total intake of timothy hay. Samples of each forage were assayed to evaluate differences in neutral detergent fiber intake. Results of the experiments examining the acceptability of teff hay were shared at a conference for forage producers and were presented at the annual meeting of the American Society of Animal Science.
Data collected in the experiments conducted in 2010 and in 2009 demonstrated that there were minimal differences in the ad libitum forage intake of pregnant and nonpregnant mares, suggesting that pregnancy does not result in increased feed intake. However, forage intake by lactating mares was greater (P<0.05) than forage intake by nonpregnant mares.These results provide objective data for making supplementation decisions for broodmares in various stages of production.
In addition the experiments examining the acceptability of teff hay found that horses preferred alfalfa to teff hay and that they preferred timothy to teff hay, when they were given a choice. However, when no choice was available, horses consumed similar amounts of teff hay and late maturity timothy hay. Horses preferred teff hay cut in earlier maturity to teff hay cut in late maturity. These data can be used by horse owners to make decisions regarding the best hay for their horses. In addition, hay producers can use the results to produce the most desirable product for horses. Three graduate students and two undergraduate students received training during this period.
Earing, J.E. B.D. Cassill, S.H. Hayes, E. VanZant, L.M. Lawence. 2010. Comparison of in vitro digestibility estimates using the Daisy II incubator with in vivo digestibility estimates in the horse. J. Anim Sci 88:3954-63
Earing, J.E., A.C. Durig, G.L. Gellin, M.D. Flythe,L.M. Lawrence. 2010. Profiling the microbial populations of mares and foals over time. J. Anim Sci 88(E-Suppl.):203
Earing, J.E., S. Hayes, M.Brummer, A. Parks, S. McCown, L.Lawrence. 2010. In vivo digestibility and mean retention time estimates of young and mature horses receiving the same diet. J.Anim Sci. 88(E-Suppl):639
McCown, S., M.Brummer, J.Earing, S. Hayes and L.Lawrence. 2010. Acceptability of teff hay by horses. J.Anim Sci. 88(E-Suppl):477.