MEAT SCIENCE AND MUSCLE BIOLOGY SYMPOSIUM--implants, muscle development, and meat quality.

Anabolic implants are routinely used in the finishing phase of beef production to improve animal performance and feed efficiency. Implanting during the feedlot phase on average increases ADG 18%, feed intake 6%, feed efficiency 8%, carcass weight 5% and ribeye area 4% compared with non-implanted controls. Implants reduce the cost of beef production, which is important given current high feed costs and beef prices. In a 1996 review of 37 implant trials, the use of a combination (estrogenic and trenbolone acetate) implant increased returns by $77 per hd compared with non-implanted steers. If calculated in today’s prices, a combination implant would increase returns by $163 per hd. However, concerns about potential negative effects of implants on marbling scores, quality grades, and tenderness exist. Changes in Warner-Bratzler shear force values of steaks from implanted steers are small (<0.5 kg) and appear related to an increase in initial tenderness, possibly due to hypertrophy of muscle fiber, instead of alterations in postmortem proteolysis. The increase in ribeye size observed with implanting may also reduce marbling scores through a dilution effect. The effect of anabolic implants on gene expression has shown that implanting downregulates certain lipogenic (SCD-1, FASN, ELOVL6) genes in steers with low quality grades (Select-) but not in implanted steers with high quality grades (Choice-). Examination of the adipocyte’s transcriptome has shown that 36 genes were differentially expressed due to implant treatment. More research is needed to further determine how anabolic implants alter lipogenic gene expression to address changes in marbling deposition with implant usage. Given our current high feed costs and cattle prices, anabolic implants are one of the most cost effective technologies that can be utilized in beef production systems.