There are multiple factors affecting a horses’ diet nutritional requirements, including type of work and physiological state of the animal. Meeting the nutritional requirements using forage-based diets can be difficult, therefore, it is important to properly balance their diets and include high-quality forages, when possible. In the absence of available pastures for grazing, horse owners must rely on hay to meet their horses’ nutritional requirements. It is important for owners to conduct hay testing to assess its quality to adjust diets.Harvest management practices directly affect the forage quality of the hay, so does the storage practices after purchasing it. There are certain assumptions horse owners may be used to rely on when purchasing hay for horses including hay color and maturity stage (with seeds), that may need to be further addressed.
Previous research has shown that increasing fiber contents within hay, specifically neutral detergent fiber (NDF) and acid detergent fiber (ADF) concentrations, have been directly linked to decreasing dry matter digestibility within horses (Hancock et al., 2014; Hansen & Lawrence, 2017). NDF is composed of the polysaccharides, hemicellulose and cellulose along with the phenolic polymer lignin (Van Soest et al., 1991; Wilson, 1994) whereas ADF is composed of just cellulose and lignin (Hancock et al., 2014). Increased fiber content within forages has been correlated to the physiological changes that take place, specifically within the cell wall of the plant, that increase with the maturity of the plant (Hoffman et al., 2003; Jung, 1989; Moore & Jung, 2001; Raffrenato et al., 2017). NDF and ADF have been used as measurements that explain forage quality because of their relationship with degradability and digestibility (Earing et al., 2010; Miyaji et al., 2008; Morgan et al., 2007). To manage forage quality within the field, the relationship between harvest practices and individual chemical composition measurements must be understood.
Bermudagrass (Cynodon dactylon) is a common type of hay used for horses and ruminants in the Southeastern United States because of its long growing season, drought toleration, and high yield (Hansen et al., 2019; Hendricks et al., 2020; Hill et al., 2001; Taliaferro et al., 2004). However, this type of hay also has a popular stigma of increasing the risk of colic in horses potentially due to its high levels of neutral detergent fiber (NDF) and acid detergent fiber (ADF) and physical characteristics of being fine stemmed (Blikslager, 2019; Hansen et al., 2019; Hansen & Lawrence, 2017; Little & Blikslager, 2002). A previous study found that increasing NDF concentrations of Coastal Bermudagrass had a negative effect on in vivo dry matter disappearance (DMD) within horses and that NDF and crude protein (CP) concentrations of this forage best predicted DMD (Hansen & Lawrence, 2017).
Horses are hindgut fermenters, where absorption of nutrients from forages occurs primarily in the cecum by microbes that break down these forages via fermentation. From findings of previous research, a significant determinant of forage quality is maturity at harvest (Darlington & Hershberger, 1968). The composition of the cecal microbiome is affected by the maturity of forages due to the changes in digestibility and nutritive value typically being drastically different for forages harvested in the beginning of the growing season versus the end (Julliand & Grimm, 2017). Forage digestibility studies in horses has typically been done using fecal in-vitro studies, which can have the potential to create different results than an in-vivo study (Muhonen et al., 2021). Future research efforts should be to understand the changes in cecal microbiome composition in response to changes in nutritive value of forages at different maturities. This information would provide horse owners and horse hay producers better guidelines for the selection and production of horse-quality hay.
References
Blikslager, A. T. (2019). Colic prevention to avoid colic surgery: a surgeon’s perspective. Journal of Equine Veterinary Science, 76, 1-5.
Darlington, J. M., & Hershberger, T. V. (1968). Effect of Forage Maturity on Digestibility, Intake and Nutritive Value of Alfalfa, Timothy and Orchardgrass by Equine. Journal of Animal Science, 27(6), 1572-1576. https://doi.org/10.2527/jas1968.2761572x
Earing, J. E., Cassill, B. D., Hayes, S. H., Vanzant, E. S., & Lawrence, L. M. (2010). Comparison of in vitro digestibility estimates using the DaisyII incubator with in vivo digestibility estimates in horses1. Journal of Animal Science, 88(12), 3954-3963. https://doi.org/10.2527/jas.2010-2989
Hancock, D. W., Saha, U., Stewart, R., Bernard, J. K., Smith, R., & Johnson, J. M. (2014). Understanding and improving forage quality. UGA Extension Bulletin, 1425, 16.
Hansen, T. L., Chizek, E. L., Zugay, O. K., Miller, J. M., Bobel, J. M., Chouinard, J. W., Adkin, A. M., Skurupey, L. A., & Warren, L. K. (2019). Digestibility and Retention Time of Coastal Bermudagrass (Cynodon dactylon) Hay by Horses. Animals : an open access journal from MDPI, 9(12), 1148. https://doi.org/10.3390/ani9121148
Hansen, T. L., & Lawrence, L. M. (2017). Composition Factors Predicting Forage Digestibility by Horses. Journal of Equine Veterinary Science, 58, 97-102. https://doi.org/https://doi.org/10.1016/j.jevs.2017.08.015
Hendricks, T. J., Tucker, J. J., Hancock, D. W., Mullenix, M. K., Baxter, L. L., Stewart Jr., R. L., Segers, J. R., & Bernard, J. K. (2020). Forage accumulation and nutritive value of bermudagrass and alfalfa–bermudagrass mixtures when harvested for baleage. Crop Science, 60(5), 2792-2801. https://doi.org/https://doi.org/10.1002/csc2.20222
Hill, G., Gates, R., & West, J. (2001). Advances in bermudagrass research involving new cultivars for beef and dairy production. Journal of Animal Science, 79(suppl_E), E48-E58.
Hoffman, P., Lundberg, K., Bauman, L., & Shaver, R. D. (2003). The effect of maturity on NDF digestibility. Focus on forage, 5(15), 1-3.
Julliand, V., & Grimm, P. (2017). The Impact of Diet on the Hindgut Microbiome. Journal of Equine Veterinary Science, 52, 23-28. https://doi.org/https://doi.org/10.1016/j.jevs.2017.03.002
Jung, H. G. (1989). Forage Lignins and Their Effects on Fiber Digestibility. Agronomy Journal, 81(1), 33-38. https://doi.org/https://doi.org/10.2134/agronj1989.00021962008100010006x
Little, D., & Blikslager, A. T. (2002). Factors associated with development of ileal impaction in horses with surgical colic: 78 cases (1986-2000). Equine Vet J, 34(5), 464-468. https://doi.org/10.2746/042516402776117773
Miyaji, M., Ueda, K., Kobayashi, Y., Hata, H., & Kondo, S. (2008). Fiber digestion in various segments of the hindgut of horses fed grass hay or silage. Animal Science Journal, 79(3), 339-346. https://doi.org/https://doi.org/10.1111/j.1740-0929.2008.00535.x
Moore, K. J., & Jung, H.-J. G. (2001). Lignin and fiber digestion.
Morgan, L. M., Coverdale, J. A., Froetschel, M. A., & Yoon, I. (2007). Effect of Yeast Culture Supplementation on Digestibility of Varying Forage Quality in Mature Horses. Journal of Equine Veterinary Science, 27(6), 260-265. https://doi.org/https://doi.org/10.1016/j.jevs.2007.04.009
Muhonen, S., Sadet-Bourgeteau, S., & Julliand, V. (2021). Effects of Differences in Fibre Composition and Maturity of Forage-Based Diets on the Microbial Ecosystem and Its Activity in Equine Caecum and Colon Digesta and Faeces. Animals, 11(8), 2337. https://www.mdpi.com/2076-2615/11/8/2337
Raffrenato, E., Fievisohn, R., Cotanch, K., Grant, R., Chase, L., & Van Amburgh, M. (2017). Effect of lignin linkages with other plant cell wall components on in vitro and in vivo neutral detergent fiber digestibility and rate of digestion of grass forages. Journal of Dairy Science, 100(10), 8119-8131.
Taliaferro, C. M., Rouquette Jr, F. M., & Mislevy, P. (2004). Bermudagrass and stargrass. Warm‐season (C4) grasses, 45, 417-475.
Van Soest, P. J., Robertson, J. B., & Lewis, B. A. (1991). Methods for Dietary Fiber, Neutral Detergent Fiber, and Nonstarch Polysaccharides in Relation to Animal Nutrition. Journal of Dairy Science, 74(10), 3583-3597. https://doi.org/https://doi.org/10.3168/jds.S0022-0302(91)78551-2
Wilson, J. (1994). Cell wall characteristics in relation to forage digestion by ruminants. The Journal of Agricultural Science, 122(2), 173-182.
Written by
Alexa Cornett, Ph.D. student
Liliane Silva, Forages Specialist
