Impact of Repetitive Use of Growth Implants on Beef Quality and Palatability:

In a large study involving 550 crossbred steer calves, Colorado State university researchers investigated the effect of repetitive use of growth implants on carcass quality and palatability attributes on beef.  Steers were allocated to 11 treatments (non-implanted Control and 10 different lifetime implant strategies).  Cattle in the 10 treated groups were implanted at some or all of five production phases (branding, weaning, backgrounding, feedlot entry, or reimplant time).  Of the 10 treated groups, two received two implants, three received four implants, and five received five implants.  Products used were Synovex-C at branding; Ralgro at weaning; Ralgro or Synovex-C at backgrounding; Synovex-C or Revalor-S during finishing.  

1. Control carcasses had significantly higher marbling scores than carcasses in all other groups.
2. Steers implanted twice had higher marbling scores than those implanted a total of four or five times.
3. Steaks from Control carcasses had lower shear force values and were rated higher by consumers for tenderness, flavor and juiciness than steaks from all other treatment groups.
4. Steaks from Control carcasses were rated as more desirable in overall eating quality than steaks from steers implanted two, three, four or five times.
5. Implanting increased average daily gain by 11.8% to 20.5% from weaning to harvest and increased carcass weight by 8.9% to 13.8% compared to controls.
6. Implants increased ribeye area and decreased percentage of kidney/pelvic/heart fat, but did not affect dressing percentage or external fat thickness.

The authors concluded that lifetime implant protocols can influence marbling and eating quality of beef and emphasized the importance of selecting implant strategies based on specific market targets for cattle.  (Platter et al.2003. J Anim. Sci. 81:984)