Effect of dietary energy density and meal size on growth performance, eating pattern, and carcass and meat quality in Holstein steers fed high-concentrate diets

Abstract

A total of 121 steers (162 ± 3.0 kg BW and 148 ± 2.7 d old) were used to study the effect of dietary energy density and meal size (limiting the amount of concentrate delivered at each feeder visit) on performance, hormones associated with the regulation of intake, and carcass and meat quality. Steers were allocated by BW to 6 pens. Each pen had the same BW mean and CV, and pens were randomly assigned to 3 treatments (2 pens/treatment): a concentrate of moderate energy density (3.23 Mcal ME/kg, 6.2% ether extract) fed for ad libitum intake with no control on meal size (CTR), a concentrate of high-energy density (3.43 Mcal ME/kg, 8.3% ether extract) fed for ad libitum intake with no control on meal size (HE), and the same high-energy concentrate offered for ad libitum intake but with meal size limited to a maximum concentrate delivery of 0.6 kg DM/visit (HELM). Body weight was recorded every 14 d; concentrate consumption and eating pattern were recorded daily. On d 163, blood samples were collected to determine serum concentrations of leptin, ghrelin, glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK), glucose, and insulin. After slaughter (on d 166 to 170), the 9-10-11 rib section was removed to estimate separable bone, lean, and fat. Meat quality of LM was analyzed. Data were analyzed using a mixed-effects model with repeated measures. Steers in the HELM treatment had a lower (P < 0.01) final BW and ADG than CTR and HE steers. Concentrate intake was greater (P < 0.001) in CTR (6.6 ± 0.10 kg/d) than in HE steers (5.7 ± 0.10 kg/d), and HELM (5.2 ± 0.10 kg/d) consumed less concentrate than CTR and HE steers. However, HE and HELM steers were more (P < 0.01) efficient than CTR steers. The mean number of daily meals and eating rate were less (P < 0.05) for HELM than for HE or CTR. At d 163, serum concentrations of GLP-1, CCK, and insulin were lower (P < 0.05), and leptin (P = 0.10) and glucose (P = 0.08) concentrations tended to be lower for HELM than for CTR or HE. Carcass conformation and HCW were less (P < 0.05) for HELM than for CTR. Although differences among treatments were observed in carcass fat cover, intramuscular fat did not differ among treatments. Limiting the amount of feed delivery per feeder visit in steers fed high-energy (fat) diets affected eating pattern, reduced total energy consumption and performance, and modified hormones related to intake compared with CTR and HE, but no effect on rib fat distribution and meat quality was observed.

Keywords: energy density; hormones; meal size.