Three finishing experiments were conducted in commercial feedlots to determine effects of implant programs on finishing heifer performance, carcass characteristics, and economics. A total of 3,307 heifers were used in the three experiments. Overall, four treatment comparisons were tested within the three separate experiments. Treatment groups included the following: 1) heifers implanted with Synovex® Plus (Fort Dodge Animal Health; Fort Dodge, IA) but not fed melengestrol acetate (MGA®; Pharmacia and Upjohn Company; Kalamazoo, MI), 2) heifers implanted with Synovex® Plus and fed MGA®, 3) heifer implanted with Revalor®-H (Intervet Inc.; Millsboro, DE) and fed MGA®, and 4) heifers implanted with Finaplix®-H (Intervet Inc.) and fed MGA®. Common treatments of Synovex® Plus and dietary MGA® as well as Finaplix®-H and dietary MGA® were used in each of the three experiments. Finishing heifers fed MGA® and implanted with Synovex® Plus had 3.9 and 4.1% greater (P<0.10) ADG than did heifers implanted with Revalor®-H or Finaplix®-H and fed MGA®, respectively. Daily gain did not differ for heifers implanted with Revalor®-H or Finaplix®-H. Feeding MGA® to heifers implanted with Synovex® Plus increased ADG and decreased deleterious effects on quality grade; however; carcasses had greater fat thickness. Fewer carcasses of heifers fed MGA® and implanted with Synovex® Plus or Revalor®-H were graded Choice in comparison with the carcasses of those implanted with Finaplix®-H. When selling heifers on a carcass-merit basis, net returns did not differ among heifers implanted with Synovex® Plus, Revalor®-H, or Finaplix®-H when fed MGA®. When selling heifers on a dressed basis, net return was maximized (P<0.10) with the use of Synovex® Plus and supplementation with MGA® compared with Synovex® Plus and no MGA® supplementation, Revalor®-H and MGA® supplementation, and Finaplix®-H and MGA® supplementation.
Crossbred, spring-calving cows (yr 1, n = 136; yr 2, n = 113; yr 3, n = 113) were used in a 3-yr experiment to evaluate the influence of supplemental protein prepartum and grazing subirrigated meadow postpartum on pregnancy rates and calf feedlot performance. A 2 × 2 factorial arrangement of treatments was used in a switchback design. From December 1 to February 28, cows grazed dormant upland range in 8 pastures (32 ± 2 ha each). The equivalent of 0.45 kg of supplement/cow per d (42% CP) was provided to half of the cows on a pasture basis 3 d/wk. For 30 d before the beginning of breeding (May 1 to May 31), half of the cows grazed a common subirrigated meadow (58 ha), and the remainder was fed grass hay in a drylot. Cow BW and BCS were monitored throughout the year, and steer calf performance was determined until slaughter. Feeding supplement prepartum improved (P = 0.01 to P < 0.001) BCS precalving (5.1 vs. 4.7) and prebreeding (5.1 vs. 4.9) and increased (P = 0.02) the percentage of live calves at weaning (98.5 vs. 93.6%) but did not affect (P = 0.46) pregnancy rate (93 vs. 90%). Calves born to dams fed supplement prepartum had similar (P = 0.29) birth weight (37 vs. 36 kg) but greater (P = 0.02) weaning weight (218 vs. 211 kg). However, steer feedlot DMI (8.53 vs. 8.48 kg), ADG (1.6 vs. 1.6 kg), and carcass weight (369 vs. 363 kg) were not affected (P = 0.23 to P = 0.89) by prepartum supplementation. Allowing cows to graze subirrigated meadow postpartum improved (P < 0.001) BCS prebreeding (5.2 vs. 4.9) but did not affect (P = 0.88) pregnancy rate (92 vs. 91%). Allowing cows to graze subirrigated meadow increased (P = 0.01) calf weaning weight (218 vs. 211 kg) but not (P = 0.62 to P = 0.91) feedlot DMI (8.4 vs. 8.3 kg), ADG (1.6 vs. 1.6 kg), or carcass weight (363 vs. 362 kg) of their steer calves. Increased percentage of live calves at weaning as a result of feeding supplemental protein increased net returns at weaning and after finishing in the feedlot. Net returns were increased by allowing cows to graze subirrigated meadow postpartum regardless of whether calves were marketed at weaning or after finishing in the feedlot.
