title: Effects of increasing concentrations of wet distillers grains with solubles in steam-flaked, corn-based diets on energy metabolism, carbon-nitrogen balance, and methane emissions of cattle.
abstract: The use of wet distillers grains with solubles (WDGS) in feedlot diets has increased in the Southern Great Plains as a result of the growing ethanol industry. Nutrient balance and respiration calorimetry research evaluating the use of steam-flaked corn (SFC)-based diets in conjunction with WDGS is limited. Therefore, the effects of increasing concentrations of WDGS in a SFC-based diet on energy metabolism, C, and N balance, and enteric methane (CH4) production was evaluated in Jersey steers fed at 2 times maintenance, using respiration calorimetry chambers. Four treatments were used in two 4 × 4 Latin square designs, using 8 steers. Treatments consisted of: 1) SFC-based diet with 0% WDGS (SFC-0); 2) SFC-based diet with 15% WDGS (SFC-15); 3) SFC-based diet with 30% WDGS (SFC-30); and 4) SFC-based diet with 45% WDGS (SFC-45). Diets were balanced for degradable intake protein (DIP) by adding cottonseed meal to the SFC-0 diet. As a proportion of GE, fecal, urinary, and CH4 energy increased linearly (P < 0.03) as WDGS concentration increased in the diet. In contrast, DE, ME, and retained energy decreased linearly (P < 0.01) as a proportion of GE as WDGS concentration increased. Increasing concentration of WDGS in the diet did not affect (P > 0.78) heat production as a proportion of GE. As a result of greater N intake, total N excretion increased linearly (P < 0.01) with increasing WDGS inclusion in the diet. Fecal C loss and CH4-C respired increased linearly (P < 0.01) when WDGS concentration increased in the diet whereas CO2-C respired decreased (linear, P = 0.05) as WDGS concentration increased. We conclude that CH4 production as a proportion of GE increases linearly (P < 0.01) when WDGS concentration in the diet is increased; however, dietary inclusion of WDGS at up to 45% seems to have no effect (P > 0.78) on heat production as a proportion of GE. The reason for a linear decrease in retained energy as WDGS increased was likely because of increased fecal energy loss associated with feeding WDGS. Total N excretion, fecal C loss, and CH4-C respired increased linearly with increasing concentration of WDGS in the diet. We determined NEg values for WDGS to be 2.02, 1.61, and 1.38 Mcal/kg when included at 15%, 30%, and 45%, respectively, in a SFC-based diet. From these results we conclude that the energy value (NEg) of WDGS in a finishing cattle diet based on SFC must be decreased as the inclusion increases.
authors.affiliation: USDA-ARS U.S. Meat Animal Research Center, Clay Center, NE 68933, USA. Kristin.Hales@ars.usda.gov
authors.forename: K E
authors.initials: KE
authors.lastname: Hales
authors.forename: N A
authors.initials: NA
authors.lastname: Cole
authors.forename: J C
authors.initials: JC
authors.lastname: MacDonald
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002244:Carbon / Q000378:metabolism*; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D004041:Dietary Fats / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D005511:Food Handling; D008297:Male; D008697:Methane / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D013213:Starch / Q000378:metabolism; D013227:Steam
chemical_list: D004041:Dietary Fats; D013227:Steam; D002244:Carbon; D013213:Starch; D009584:Nitrogen; D008697:Methane