Effects of Dietary Glycerin Inclusion at 0%, 5%, 10%, and 15% of Dry Matter on Energy Metabolism and Nutrient Balance in Finishing Beef Steers
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% in dry-rolled corn (DRC)-based 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. Diets were based on DRC and GLY 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, 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 < 0.01) to respond quadratically. 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 proportion 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. The increase in N excretion as GLY increased in the diet could indicate an increase in microbial N excretion caused by a shift from ruminal fermentation to post gastric fermentation. USDA is an equal opportunity provider and employer.
Keywords: cattle, energy metabolism, glycerin