Effects of Dry Matter Intake Restriction on Growth Performance and Carcass Merit of Finishing Steers1

Two studies were conducted to determine the effects of restricting DMI on growth performance and carcass merit of finishing steers. In Trial 1, 84 Angus cross steers (BW = 313 ± 7 kg) were randomly assigned to one of three treatment diets that were designed to achieve a 1.6 kg/d ADG at three intake levels: ad libitum, 90% of ad libitum DMI (LF90), or 80% of ad libitum DMI (LF80). In Trial 2, 84 Angus cross steers (BW = 327 ± 20 kg) were randomly assigned to one of two treatment diets that were designed to achieve an ADG of 1.6 kg/d at two intake levels: ad libitum or LF80. All diets delivered similar total NE, metabolizable protein, and P per day. Daily feed delivery (0800 h) for each treatment was determined based on a rolling 5-d average of DMI by steers fed ad libitum. No steers were treated for digestive disorders in either trial, and liver abscess scores were similar between treatments (Trial 1, P=0.65; Trial 2, P=0.73). Actual average DMI during Trial 1 were 2.45% BW for ad libitum steers, 2.26% BW for LF90 (92% of ad libitum intake), and 1.99% BW for LF80 (81% of ad libitum intake). During Trial 2, actual average DMI was 2.43% BW for ad libitum steers and 1.94% BW for LF80. Steer ADG was greater (P≤0.04) for LF80 than for ad libitum feeding during both trials. Similarly, growth efficiency [gain to feed ratio; G:F] by LF80 steers was greater (P<0.01) than that of ad libitum steers during both trials. During Trial 1, hot carcass weights of LF80 steers were greater (P=0.01) than those for ad libitum steers or for LF90 steers. Marbling scores of ad libitum steers and for LF80 steers were greater (P<0.05) than those for LF90 steers. Yield grade tended to be more favorable (P=0.11) in ad libitum steers and for LF90 steers compared with LF80 steers. Hot carcass weights, marbling scores, and yield grades were similar between treatments in Trial 2. Growth performance was greater than that predicted by NRC models when finishing steers were fed a diet formulated to promote 1.6 kg/d ADG but limited to approximately 80% of ad libitum DMI.