Nutritional and management strategies for feedlot cattle.

摘要

Four experiments were conducted to evaluate effects of different nutritional and management strategies on feedlot cattle.;Experiment 1 used 642 Angus-cross heifers fed six finishing diets based on SFC with 0% or 20% WSC replacing SFC, and 0, 15, or 30% WDGS replacing SFC (DM basis). No WSC x WDGS interactions (P ≥ 0.08) occurred for DMI, ADG, G:F, and carcass characteristics. Heifers fed diets containing 20% vs. 0% WSC had greater (P < 0.01) DMI, but final BW, ADG, and G:F were not affected (P ≥ 0.11). The percentage of carcasses grading USDA choice or better tended to be lower (P = 0.07), and the percentage grading USDA select were greater (P = 0.03) for cattle fed diets with 20% vs. 0% WSC. Other carcass characteristics, morbidity, and mortality were not affected (P ≥ 0.16) by WSC. In summary, substituting SFC with 20% WSC in finishing diets did not affect animal performance and feed conversion, but decreased carcass quality.;Experiment 2 used 718 Angus-cross heifers (average BW = 265 +/- 27.8 kg). Treatments were daily supplementation with 0, 7.5, 15.0, and 22.5 g of RPMET per heifer (estimated to supply 0, 4, 8, and 12 g/d of metabolizable DL-Met, respectively) that was mixed with the diet for a treatment group of cattle before feeding. Supplementation did not affect (P ≥ 0.35) serum insulin or plasma urea-N concentrations. Supplementing a wet corn-gluten feed-based diet with RPMET improves performance of heifers during the growing phase.;Experiment 3 used 408 Angus-cross heifers (200 +/- 0.8 kg BW). Treatments were: 1) no implant (CON); 2) an implant (Revalor-H; 140 mg trenbolone acetate and 14 mg estradiol; Intervet/Schering-Plough Animal Health) at initial processing (IMP!); and 3) an implant (Revalor-H) 21 d after initial processing (IMP21). Implant strategy did not affect (P = 0.59) serum haptoglobin concentrations, but the concentrations were greater (P < 0.01) on d 1 than on d 21 and d 43. A treatment x day interaction ( P = 0.01) occurred for serum IGF-I, such that concentrations were not different on d 1, greater for IMP1 than CON and IMP21 on d 21, and greater for IMP21 than CON on d 42. Prolactin was not affected by implant strategy, but concentrations were greater (P < 0.01) on d 21 than d 0 and 42. From d 0 to 21, DMI of heifers was not affected (P = 0.34), and ADG was greater (P < 0.05) for IMP1 (1.03 kg/d) than CON (0.86 kg/d) and lesser (P < 0.05) for IMP21 (0.65 kg/d) than CON.;Experiment 4 used 312 crossbred heifers (184 +/- 0.7 kg BW). A TIME x CTC interaction (P = 0.06) occurred for DMI; DMI was lower for DELAYED than INITIAL when heifers received -CTC, but DMI was not different between DELAYED and INITIAL when heifers received +CTC. No TIME x CTC interactions (P ≥ 0.21) occurred for BW, ADG, or G:F. Timing of BVD vaccine and implant did not affect (P = 0.18) BW of heifers on d 28, but BW were lower (P = 0.04) for DELAYED than INITIAL heifers on d 56. From d 29 to 56, ADG was lower ( P = 0.02) and G:F tended to be lower (P = 0.07) for DELAYED than INITIAL heifers. Delaying the BVD vaccine and implant also tended to lower (P = 0.09) ADG from d 1 to 56, but did not affect (P = 0.27) G:F. On d 28, BW of +CTC heifers tended to be lower (P = 0.06) than -CTC heifers, but CTC did not affect (P ≥ 0.21) d-56 BW, ADG, or G:F. Morbidity and mortality during the 56 d were not affected (P ≥ 0.17) by treatments. Delaying the initial BVDV vaccine and growth implant with or without CTC may not improve animal health, and may have negative implications on performance of newly received feedlot heifers. (Abstract shortened by UMI.).