Effect of winter growing program on subsequent feedlot performance, body composition, carcass merit, organ mass and oxygen consumption in beef steers

Abstract

Effect of winter growing program on finishing performance, body composition, carcass merit, organ mass and oxygen consumption of beef steers was investigated. Four steers were randomly selected as an initial harvest group. Remaining steers were blocked by weight and randomly allotted to one of four treatment groups: 1) ad libitum fed high-concentrate diet (CF); 2) grazed on wheat pasture (WP); 3) fed a sorghum silage-based growing diet (SF); or 4) program fed a high-concentrate diet (PF). Steers in the WP, SF, and PF groups were managed to achieve approximately equal rates of body weight gain. After 112 d steers in the WP, SF, and PF treatments were adapted to a high-concentrate diet for finishing. Steers from all treatments were harvested at a backfat of 1.27 cm. In addition six steers from each treatment were randomly selected for harvest at the end of the growing and finishing phases. During the finishing phase DMI was greater (P<0.01) for SF steers (10.9 kg/d) than PF steers (10.1 kg/d) with WP steers being intermediate (10.4 kg/d). Steers in the SF and PF groups had greater (&lt;em&gt;P&lt;/em&gt; &lt; 0.01) ADG (2.02 and 1.85 kg/d, respectively) and greater gain:feed (both 0.186) compared with WP steers (1.64 kg/d and 0.156). At the end of the growing phase liver, kidney and small intestine weights (g/kg EBW) were greatest for WP steers (P<0.01). Silage-fed steers had the heaviest (P<0.05) reticulo-rumens. Mesenteric fat and viscera mass was greatest for PF, intermediate for SF, and lowest for WP steers (P< 0.01). At final harvest, liver weights remained greatest (g/kg EBW; P<0.01) for WP steers and mass of total splanchnic tissue was not different. In conclusion, SF and PF steers had greater gains and gain efficiency during finishing compared with WP steers due to greater energy demand of visceral tissue growth during finishing for WP steers. Steers in the SF group had more growth in visceral tissues during finishing as compared to PF steers but compensated with greater intake.