Date of this Version
The Professional Animal Scientist 19 (2003): 159-170
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.