EFFECT OF TRENBOLENE ACETATE ESTRADIOL IMPLANTS AND ESTRUS SUPPRESSION ON GROWTH-PERFORMANCE AND CARCASS CHARACTERISTICS OF BEEF HEIFERS

The effects of estrus suppression (none, oral melengestrol acetate (0. 4 mg d(-1)) or ovariectomy via Willis spay technique) and an anabolic implant (none or Synovex Plus(R)) on growth performance and carcass ch aracteristics were determined using 90 beef heifers of composite breed ing in a 2 x 3 factorial experiment conducted in the last 50 d before slaughter. Spaying caused no morbidity or mortality and resulted in av erage daily gains(1.37 kg d(-1)) comparable to heifers fed melengestro l acetate (1.33 kg d(-1)). Implanting improved (P < 0.05) feed efficie ncy and increased (P < 0.05) animal gain, ribeye area, carcass weight and yield and reduced (P < 0.05) intramuscular fat deposition but estr us suppression did not. Method of estrus suppression did not influence (P > 0.05) carcass traits. Spaying and implanting represent an effect ive means of improving returns from heifers, even late in the finishin g period.