EFFICACY OF CHEMICAL CASTRATION AND EFFECTS OF AGE AT CASTRATION AND IMPLANT REGIME ON GROWTH-RATE, TESTICULAR MEASUREMENTS AND TESTOSTERONE LEVELS OF BEEF-CALVES

In 1984-1985 and 1985-1986, groups of 136 and 127 male calves were used to assess the effects of multiple implants (Ralgro or Steeroid), castration time (early or late) and castration method (surgical or chemical) on testicular development and weight gain for 28 d following castration. Ralgro-implanted bull calves had smaller scrotal circumference (P < 0.001) and testicle weight (P < 0.001) than nonimplanted calves at early castration (59 +/- 1 d), late castration (157 +/- 1 d) and at slaughter (459 +/- 3 d). Steeroid had no effect on testicle weight at early castration (40 +/- 1 d) but reduced testicle weight (P < 0.001) at late castration (148 +/- 1 d). Average daily gain (ADG) during the first 7 d postcastration was less for surgically castrated than chemically castrated calves or bulls following early castration (P < 0.05) but in the 7 d following late castration, bull calves grew faster than surgical castrates (P < 0.05) and surgical castrates grew faster than chemical castrates (P < 0.05). The ADG of calves implanted with Ralgro was greater than that of nonimplanted calves during the 28-d period following early and late castration (P < 0.05) but Steeroid had no effect (P < 0.05) on 28-d postcastration ADG. Chemical castration increased scrotal circumference at 7, 14 and 28 d postcastration (P < 0.001) but by day 56, testicular atrophy was complete in those calves that were successfully castrated. Chem-cast was an effective method of castration in young calves (< 90 kg liveweight), particularly those that had been implanted with Ralgro, but efficacy was reduced (P < 0.05) in older calves (> 150 kg liveweight).