Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2014
Publication Date: 1/9/2015
Publication URL: http://handle.nal.usda.gov/10113/60163
Citation: Hales, K.E., Foote, A.P., Brown-Brandl, T.M., Freetly, H.C. 2015. Effects of dietary glycerin inclusion at 0, 5, 10, and 15 percent of dry matter on energy metabolism and nutrient balance in finishing beef steers. Journal of Animal Science. 93(1):348-356.
Interpretive Summary: Expansion of the biodiesel industry in the United States has increased the supply of glycerin. Glycerin is energy dense and can be fed to cattle; however, the energy value is not known. Therefore, the effects of dietary glycerin inclusion at 0%, 5%, 10%, and 15% on energy metabolism in beef cattle were evaluated. Cattle intake was decreased when glycerin intake increased. Also, cattle lost less energy in the feces as glycerin inclusion increased in the diet, meaning that glycerin was more digestible than the corn it replaced in the diet mixture. Cattle consuming the diet with 15% glycerin retained the least amount of overall energy and nitrogen within the body. There is a high metabolic cost associated with including glycerin in cattle diets at greater than 10% of dry matter. To optimize animal performance, glycerin should not be fed at greater than 10% in beef cattle diets.
Technical Abstract: Expansion of the biodiesel industry has increased the glycerin (GLY) supply. Glycerin is an energy-dense feed that can be used in ruminant species; however, the energy value of GLY is not known. Therefore, the effects of GLY inclusion at 0%, 5%, 10%, and 15% on energy balance in finishing cattle diets were evaluated in 8 steers (BW = 503 kg) using a replicated Latin square design. Data were analyzed with the fixed effects of dietary treatment and period and random effects of square and steer within square were included in the model. Contrast statements were used to separate linear and quadratic effects of GLY inclusion. Glycerin replaced DRC at 0% (GLY-0), 5% (GLY-5), 10% (GLY-10), and 15% (GLY-15) of dietary dry matter. Dry matter intake decreased linearly (P = 0.02) as GLY increased in the diet. As a proportion of GE intake, fecal energy loss tended to decrease linearly (P < 0.07), and DE also tended to decrease linearly (P = 0.07) as dietary level of GLY increased. Urinary energy loss was not different (P > 0.31) as a proportion of GE as GLY increased in the diet. Methane energy loss as a proportion of GE intake tended to respond quadratically (P = 0.10) decreasing from 0% to 10% GLY inclusion and increasing thereafter. As a proportion of GE intake, ME tended to respond quadratically (P = 0.10), increasing from 0% GLY to 10% GLY and then decreasing. As a proportion of GE intake, heat production increased linearly (P = 0.02) as GLY increased in the diet. Additionally, as a proportion of GE intake, retained energy (RE) tended to respond quadratically (P = 0.07) increasing from 0% to 10% GLY inclusion and decreasing thereafter. Total dry matter digestibility tended (P < 0.10) to respond quadratically increasing at a decreasing rate from 0% to 5% GLY inclusion. As a proportion of N intake, urinary and fecal N excretion increased linearly (P < 0.04) as GLY increased in the diet. Furthermore, g of N retained and N retained as a % of N intake both decreased linearly (P < 0.02) as GLY increased in the diet. Overall, RE tended to decrease as GLY increased in the diet in conjunction with a decrease in N retention, which could indicate an increased metabolic cost to the animal associated with feeding GLY. Based on RE, the feeding value of GLY in high-concentrate diets is greater than DRC at 5% and 10% of DM, but less at 15% of DM.