Effects of nutrition, sex of calf and breed type on response to zeranol: preweaning growth

Abstract

An experiment was conducted to evaluate the effects of breed, sex and plane of nutrition on the growth response to zeranol in Angus and crossbred calves prior to weaning. Eighty-eight heifers and 118 steers received either a high or low plane of nutrition using a first and last grazing technique. Half of the calves in each nutrition group received a zeranol implant (36 mg) at an average age of 3.4 mo. Both zeranol and the higher level of nutrition increased (P less than .001) growth rate prior to weaning (7.4 mo of age). Zeranol did not affect hip height at weaning (P greater than .1), but calves on the higher plane of nutrition were taller (P less than .01) than calves on the lower plane of nutrition. The zeranol x nutrition interaction was not significant (P greater than .1) for growth rate or hip height. Steers grew faster (P less than .01) preweaning and were taller (P less than .01) at weaning than heifers. Crossbred calves gained more rapidly (P less than .001) preweaning and were taller (P less than .001) at weaning than Angus calves were. Neither sex nor breed interacted with zeranol to influence any of the traits examined. Based on these results we conclude that preweaning growth was affected by zeranol and this effect was consistent across sexes, breeds and planes of nutrition tested.

Influence of incremental zeranol implant doses on the chemical and physical characteristics of third metacarpal bone and chemical composition of liver and soft tissue from feedlot steers.

“…These results parallel those obtained with estradiol-implanted lambs in which no affect on metacarpal fresh weight or length were observed (Field et al, 1990). Prichard et al (1989) found no effect of zeranol on calf frame score, and Woods et al ( 1990) found no effect of zeranol on hip height at weaning in steers or heifers. Bagley et al ( 1989) found that zeranol implantation of steer calves shortly after birth resulted in increased cannon bone circumference at weaning, but shorter leg lengths.…”

Sweet potato and Green panic as sole fodder for stall-fed lactating White Fulani cows and growing calves

“…The results were similar to that by Reynolds et al (1982) who showed from their study on preweaning growth rate and weaning traits that crossbred calves exceeded straightbred (or purebred) calves by 25.2% in average daily gain and 23.1% in weaning weight. In a related study, it was reported that crossbred calves exhibited more rapid preweaning gains and were taller at weaning compared to their straightbred Angus calves (Woods et al 1990). The observed negative correlation between milk intake and dry matter intake is expected as the calves matured since their rumens become more mature for forage / roughage ingestion and digestion.…”

Effect of nursing-calf implant timing on growth performance and carcass characteristics1

“…greater when suckling calves are on a higher plane of nutrition. In a study conducted by Woods et al (1990), zeranol implants resulted in an increased ADG of nursing steer and heifer calves compared with nonimplanted controls; however, weaning weight only tended to increase (P < 0.08). Mader et al (1985) reported no difference in weaning weight when zeranol implants were administered to suckling calves compared with nonimplanted controls and that preweaning implants may depress the subsequent response of postweaning implants.…”