Effect of anabolic steroids, alone or in combination with antibiotics, on bull performance, carcass traits and meat quality characteristics.

Two trials were conducted with 32 and 39 finishing Belgian white-red bulls, treated with anabolic agents during 55 to 60 days prior to slaughter. Xenobiotic androgens and estrogens, together with (Exp. I) or without progesterone (Exp. II) were injected at three-week intervals. Diets consisted of maize silage and 7.5 g concentrate daily per kg liveweight. Half of the animals within each experiment received an antibiotic for the entire fattening period lasting about 285 days. Lasalocid-sodium (Exp. I) and virginiamycin (Exp. II) were incorporated at 65 mg per kg concentrate. Anabolic agents improved average daily gain from 1.06 to 1.20 kg (P less than 0.10) and from 1.24 to 1.42 kg (P less than 0.05) respectively. In both trials steroidal growth promoters stimulated intake and improved feed efficiency (P less than 0.10). Feed antibiotics did not significantly affect daily gain during this short term finishing period. A reduced feed intake (P less than 0.05) and improved feed conversion were observed for lasalocid, while there was no difference for virginiamycin. Dry matter intake amounted to 80.5 and 76.3 g per kg metabolic weight and 9.02 and 8.41 kg per kg gain, respectively for control and lasalocid treated animals. The data were 79.6 and 80.3 g and 7.30 and 7.34 kg, respectively, for the experiment with virginiamycin. No significant interaction between anabolics and antibiotics was obtained with respect to gain and feed efficiency. Dressing percentage, carcass composition, carcass grading and meat traits were not affected by anabolic treatment or antibiotic supplementation.