135 Growth Performance, Carcass Characteristics, and Methane Emissions of Feedlot Young Bulls

Abstract

Abstract The growth performance, carcass characteristics, and methane emissions from feedlot beef cattle fed a high-lipid finishing diet (7.3% of ether extract) were evaluated. Fifty long-yearling young bulls were divided into two groups following their breed composition: Nellore (n = 25) and Angus × Nellore crossbred (n = 25), and randomly assigned into 4 pens (12 or 13 animals/pen) following a completely randomized design. Animals were sourced from the same breeding season and endured a grazing growing phase in Megathyrsus maximus cv. Mombaça pasture, with protein and energy supplement offered at 0.2% of body weight (BW). The feedlot phase comprehended 105 days of feed, and the diet (80% concentrate) was formulated to meet or safely exceed the beef cattle requirements to target an average daily gain (ADG) of 1.6 kg/day, in which major ingredients were represented by (% DM basis): sorghum silage (20%), ground corn (57.6%), ground soybean seed as the lipid source (20.4%), and a mineral/vitamin premix (2%). Titanium dioxide (TiO2) was used as an external marker to estimate dry matter intake (DMI), while 10 g was administered to 12 animals of each group, once daily, for 10 d. Animals were weighed every 30 d after a 16-h fasting period, and the day before slaughter to obtain the final body weight (FBW). Enteric methane emissions were measured using the sulfur hexafluoride (SF6) tracer gas technique in the same animals used for intake measurements. The animals were equipped with gas collection halters attached to pre-evacuated polyvinyl chloride (PVC) sampling canisters with a capillary tube (0.127 mm diameter), made to permit 50% filling in 24 h, for five consecutive days. Data were analyzed using the statistical analysis software R (R CORE TEAM, 2021), and the effect of breed on carcass traits and methane emissions was evaluated using the completely randomized design one-way, in which treatment means were compared by the F test (P < 0.05). The crossbred animals had a greater DMI (12.6 vs.0.6 kg/d), gain efficiency (0.16 vs. 0.14), initial BW upon feedlot phase (509.8 vs. 444.7 kg), FBW (720.8 vs. 595.6, kg), ADG (2.01 vs..44 kg), and hot carcass weight (404.7 vs. 345.0 kg; P < 0.01) compared with Nellore cattle. No difference was observed in dressing percentage between genetic groups (P = 0.28). Nellore animals produced more methane expressed as CH4 g/kg ADG (266.0 vs.73.4; P < 0.01), and tended to produce more methane expressed as CH4 kg/DMI (35.4 vs. 27.7; P = 0.08), and CH4 g/kg CW (1.09 vs. 0.87; P = 0.11). Crossbred F1 Nellore/Angus young bulls showed improved feedlot performance and carcass weight, while not negatively affecting total CH4 production, but rather lessening CH4 emissions per unit of beef produced.