Abstract

BARAJAS CRUZ, Rubén et al. Influence of hormonal implant failure on feedlot performance of fattening bulls. Zootecnia Trop. [online]. 2010, vol.28, n.2, pp.193-200. ISSN 0798-7269.

Ninety four Brahman crossed bull calves (335 ± 4,74 kg) were used with the objective of determinate the effect of hormonal implant failure on growth performance response of fattening bulls in the Northwest of Mexico. In a complete randomized block design, bulls were weighed and re-implanted in left ear with 120 mg of trenbolone acetate and 24 mg of estradiol, placed in 12 ground pens and feeding a finishing diet. After 73 d they were sacrificed, ear removed and implant condition was evaluated. The criteria were: a) Absorbable implants (normal, broke or stocked); and b) Not absorbable implants (encapsulated, abscessed, or not found). Implant failure was (P < 0,01) was 32,98%. Body weight gain diminished (P < 0,01) 12% by implant failure (101,89 vs. 90,94 kg), and average daily gain decreased (P = 0,02) 10,4% (1,39 vs. 1,26 kg/d). Implant failure tended to decrease (P = 0,08) 2% carcass weight (258,4 vs. 253,3 kg) and 5% marbling grade (P = 0,06). Carcass dressing and kidney pelvic and heart-fat were not affected (P > 0,48). It is concluded, that during hot and raining season implant failure is higher than 30%, and diminish weight gain and carcass weight of finishing bulls.

Keywords : bovines; feedlot performance; hormonal implant.

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