Effects of energy supplementation on energy losses and nitrogen balance of steers fed green-chopped wheat pasture I. Calorimetry

Authors: SHRECK, ADAM - Oak Ridge Institute For Science And Education (ORISE); EBERT, PAKE - West Texas A & M University; BAILEY, ERIC - West Texas A & M University; JENNINGS, JENNY - Texas Agrilife Research; CASEY, KEN - Texas Agrilife Research; COLE, NOEL - Retired ARS Employee; Meyer, Beverly

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2017
Publication Date: 5/5/2017
Citation: Shreck, A., Ebert, P., Bailey, E., Jennings, J., Casey, K., Cole, N.A., Meyer, B.E. 2017. Effects of energy supplementation on energy losses and nitrogen balance of steers fed green-chopped wheat pasture I. Calorimetry. Journal of Animal Science. 95(5)2133-2143. https://doi.org/10.2527/jas.2017.1417.
DOI: https://doi.org/10.2527/jas.2017.1417

Interpretive Summary: In the Southern Great Plains cattle are frequently grazed on wheat to obtain inexpensive gains. These cattle are sometimes provided an energy supplement to increase weight gains and increase carrying capacity of the pasture. The effects of these management strategies on greenhouse gas emissions and energetics is not known. Therefore, scientists from ARS (Bushland, TX.), West Texas A&M University and Texas A&M AgriLife Research conducted a study with British cross-bred steers in respiration calorimetry chambers to evaluate methane emissions, energy losses, protein metabolism, and nutrient digestibility of greenchop wheat forage as affected by energy supplementation. No difference was observed for organic matter, fiber, or energy digestibility. Steers not supplemented had greater oxygen consumption and tended to have greater methane production (35.2 versus 28.9 gallons per day). Methane production, as a proportion of energy intake, was not affected by supplementation. Under the conditions of this study, energy supplementation to steers fed green-chopped wheat forage did not alter energy losses or calculated net energy values.

Technical Abstract: Providing an energy supplement to cattle grazing high-quality wheat pasture can increase average daily gain; however the effects on greenhouse gas emissions are not known. Therefore we used 10 British cross-bred steers (initial weight: 206 ± 10.7 kg) in a respiration calorimetry study to evaluate the effects of energy supplementation on energy losses, nitrogen balance, and nutrient digestibility of steers fed greenchop wheat forage. The study was a 2 x 2 factorial arrangement of treatments with dietary factors consisting of either greenchop wheat forage with no supplementation (CON) or with a steam flaked corn-based energy supplement (that also contained monensin sodium) fed at 0.5% of body weight daily (SUP)] and energy intake levels of 1-times (1x) or 1.5 times maintenance requirements (1.5x). Wheat forage was harvested daily and fed as green chop to steers continuously during the 56 d study. Supplementation did not affect digestibility of organic matter, gross energy, or fiber, or heat production. Steers not supplemented had greater (P = 0.01) oxygen consumption and tended to have (P = 0.06) greater enteric methane production than SUP steers. Methane as a proportion of gross energy intake for CON and SUP were 6.87% and 6.07%, respectively (P = 0.27). No difference (P = 0.39) in retained energy as a proportion of GE intake was noted (18.14% vs. 21.26%) between treatments. Under the conditions of this study, energy supplementation to steers fed green chopped wheat forage did not alter energy losses or calculated net energy values.