Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/2008
Publication Date: 2/2/2009
Citation: Hess, B.W., Lake, S.L., Gunter, S.A. Using glycerin as a supplement for forage-fed ruminants. J. Anim. Sci. 86(E-Suppl.2):392. (Abstract)
Technical Abstract: The utility of crude glycerin as a feed additive for forage–fed ruminants depends largely on how well the animals are able to utilize the glycerol and other dietary components when crude glycerin is added to the diet. Several studies have demonstrated that ruminal fermentation of pure glycerol results in the production of VFA, with propionate and butyrate being most prominent. No effect of up to 1% pure glycerol on the growth, adhesion, and cellulolytic activity of 2 rumen cellulolytic bacterial species has been observed in a pure culture in vitro system. However, growth and cellulolytic activity of the 2 bacterial species were greatly inhibited at a concentration of 5% pure glycerol. It has been reported that pure glycerol can comprise 13.3% of the diet without affecting diet digestibility when the in vitro system was inoculated with ruminal microorganisms, and OM fermentation increased if microbes were adapted to glycerol. With the exception of annual cool–season grasses, our in vitro experiments indicate that up to 15% crude glycerin may be added to various feedstuffs without affecting DM or fiber digestibility. Although lag time for NDF disappearance tended to decrease linearly (P = 0.07) as crude glycerin increased to 30% of the in vitro substrate, rate and extent of DM, N, and NDF disappearance were largely unaffected by inclusion of crude glycerin in the substrate. Other researchers observed either no effect or a positive effect on nutrient digestibility with up to 20% crude glycerin in diets containing a low-starch concentrate. Preliminary results from a study with prepuberal beef heifers indicate that ADG is comparable between diets with 25% crude glycerin and a soybean hull-based supplement. Furthermore, substituting wheat grain with crude glycerin of different purities to provide glycerin at about 9% of the dietary DM did not influence nutrient disappearance from the total tract of steers. Thus, crude glycerin is a viable feed additive for ruminants consuming roughage–based diets.