| Abstrakt: |
The objective of this study was to determine how weaning age and length of lipid supplementation effected growth, circulating metabolites, and carcass quality of young steers. Calves from a single AI sire were early weaned (EW; n= 24) at 150 ± 11 d of age or traditionally weaned (TW; n= 24) at 210 ± 11 d of age. Following a 2-wk adaptation period, steers were assigned to control (CON; n= 12/weaning group) or rumen bypass lipid (RB; Essentiom; n= 12/weaning group) treatment and then fed for either 45 (n= 6/treatment) or 90 d (n= 6/treatment). Treatments were formulated to be isocaloric and isonitrogenous. Steer BW was recorded on d −14 and −7 (relative to treatment), and then BW and blood samples were taken on d 0, 22, 45, 66, and 90. After treatment, steers were harvested at a commercial processing plant. The right rib section of each animal was collected for proximate analysis. Data was analyzed in a 2 × 2 × 2 factorial with all significant interactions in the model using SAS. Circulating metabolites were analyzed as repeated measures. Steers fed RB had increased plasma glucose compared with CON steers (P= 0.03; 72.1 and 67.9 ± 1.7 mg/dL, respectively). Serum triglyceride concentrations were increased in RB steers vs. CON steers (P= 0.02) and in TW steers compared with EW steers (P= 0.03; 14.3 ± 1.5). Serum cholesterol concentrations were increased (treatment × day, P= 0.01) in RB steers over CON steers from d 22 to 90 of treatment. Traditionally weaned steers had a greater HCW than EW steers (143.7 ± 2.8 and 142.0 ± 2.8 kg, respectively; P< 0.0001). Steers fed for 90 d also had greater HCW than 45-d steers (153.4 ± 2.8 and 132.3 ± 2.8 kg, respectively; P< 0.0001). The longissimus dorsi from RB steers had an increased EE compared with CON steers (3.6 ± 0. 2 vs. 2.4 ± 0. 2% on a wet basis; P< 0.0001). Also, longissimus dorsi from 90-d steers had greater (P= 0.02) concentration (3.3 ± 0.2%) of lipid than those fed for 45 d (2.7 ± 0.2%). These data show that RB supplementation increases circulating glucose, cholesterol, and triglyceride concentrations as well as marbling content of the longissimus dorsi in young steers. Furthermore, a longer period of supplementation results in increased IM adipose concentration and increased HCW. |
