Location: Rangeland and Pasture ResearchTitle: Using carbon emissions and oxygen consumption to estimate energetics parameters of cattle consuming forages Author
|Burrus, Colleen - Southern Arkansas University|
|Gregorini, Pablo - Lincoln University - New Zealand|
Submitted to: American Dairy Science Association (ADSA) - American Society of Animal Science (ASAS) Joint Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2018
Publication Date: N/A
Technical Abstract: To evaluate newer indirect calorimetry system to quantify energetic parameters, 8 cross-bred beef steers (initial BW = 241 ± 4.10 kg) were used in a 77-d experiment to examine energetics parameters calculated from carbon dioxide (CO2), methane (CH4), and oxygen (O2) fluxes. Steers were individually fed in a pen equipped with Calan head gates. After a 2 wk training period, steers were randomly assigned to 1 of 3 treatments, in multiples of maintenance ME intake (MEx, 7.43 Mcal/d): 1.1 (1.1M, n = 3), 1.4 (1.4M, n = 2), and 1.8 (1.8M, n = 3) (GE intake = 17.4, 23.1, and 31.4 Mcal/d, respectively). Diets were long-stemmed wheat hay (Triticum aestivum L.; 15% CP, 64% TDN) plus a daily supplement of 1.025 kg of alfalfa-based pellets (Medicago sativa L.; 14% CP, 69% TDN) delivered via an automated head-chamber system (GreenFeed, C-Lock, Inc., Rapid City, SD) that measured fluxes of CO2, CH4, and O2. On d 1 and 77, BW was recorded after a 17-h fast to access BW gain. Heat production (HP) was calculated from gas fluxes and predicted urinary N excretion using the Brouwer (1965) equation. Dependent variables were analyzed with the MIXED procedure (SAS Inst., Inc.; Cary, NC) and least-squares means separated with linear and quadratic contrast for unequally-spaced treatments. Both BW gain and HP linearly increased (P < 0.01) with MEx (9.2, 22.3, and 50.1 kg, and 11.4, 11.8, and 13.3 Mcal/d, respectively). Energy losses from urinary N excretion linearly increased (P < 0.01) with MEx (1.64, 2.19, and 2.98 Mcal/d, respectively), but CH4 emissions did not differ (P > 0.41; 2.15, 2.24, and 2.24 Mcal/d, respectively). The percentages of energy losses from urinary N and CH4 decreased linearly (P < 0.02) with increasing MEx (9.4, 9.5, and 9.5%, and 12.1, 11.1, and 8.9% of GE intake, respectively). Percentage of HP decreased linearly (P < 0.01; 66.1, 50.8, and 42.1% of GE intake, respectively) with increased MEx. The percentages of CH4 and urinary energy loss, and HP relative to GE intake are similar to other reports for steer consuming forages (Kurihara et al., 1999; Br. J. Nutr. 81:227-234). These results indicate that measurements of gas fluxes with this indirect calorimetry system produce estimates that are similar to researchers using respiration chamber.