Deutscher G H, Zerfoss L L, Clanton D C
J Anim Sci. 1986 Apr;62(4):875-86. doi: 10.2527/jas1986.624875x.
Zeranol implants were administered to 250 crossbred heifer calves at 1, 6 or 9 mo of age to evaluate growth, reproduction and calving performance. Heifers were assigned to eight treatment groups with 25 animals per group. Two additional groups of 25 heifers each were used to study the effects of multiple implants at two levels of nutrition on heifer performance. Implants at 1 mo of age (branding) increased heifer weights at 6 mo of age (weaning) by 5 kg (P = .08). Heifers receiving a combination of two implants gained faster (P less than .05) from weaning to breeding (6 to 13 mo) than controls or heifers implanted three times. Implants at either 6 or 9 mo increased (P less than .05) precalving pelvic areas (247 vs 241 cm2 and 248 vs 240 cm2 over controls, respectively). Implants did not affect the percent of heifers reaching puberty prior to breeding season. Conception rates in 62 d of breeding were comparable for implanted and control heifers (93 vs 96%), with the exception of heifers receiving implants at both 1 and 6 mo of age (56%). Calf birth weight, dystocia score, cow rebreeding rate and calf weaning weight were not affected by implant treatments. Heifers that received three implants and were fed at a high nutritional level (gained .62 vs .49 kg/d for regular level after weaning) tended (P greater than .10) to reach puberty at a higher rate prior to breeding and to have a higher total conception rate than implanted heifers on the regular nutrition level.
给250头杂交小母牛犊在1月龄、6月龄或9月龄时植入玉米赤霉醇，以评估其生长、繁殖和产犊性能。小母牛被分为8个处理组，每组25头。另外两组各25头小母牛用于研究两种营养水平下多次植入对小母牛性能的影响。1月龄（烙印期）植入玉米赤霉醇使小母牛在6月龄（断奶时）体重增加了5千克（P = 0.08）。接受两次植入组合的小母牛从断奶到配种（6至13月龄）比对照组或接受三次植入的小母牛增重更快（P < 0.05）。6月龄或9月龄植入均使产犊前骨盆面积增加（P < 0.05）（分别比对照组增加247平方厘米对241平方厘米和248平方厘米对240平方厘米）。植入未影响配种季节前达到青春期的小母牛百分比。植入组和对照组小母牛在62天配种期的受孕率相当（93%对96%），但1月龄和6月龄均植入的小母牛除外（56%）。植入处理对犊牛出生体重、难产评分、母牛再次配种率和犊牛断奶体重无影响。接受三次植入且高营养水平饲养的小母牛（断奶后日均增重0.62千克，而常规水平为0.49千克）在配种前达到青春期的比例更高（P > 0.10），且总受孕率高于常规营养水平的植入小母牛。
