Greathead K D
Department of Agriculture, Albany, Western Australia.
Aust Vet J. 1987 Dec;64(12):362-4. doi: 10.1111/j.1751-0813.1987.tb09601.x.
Three groups of beef steer calves were implanted in 1983 with 36 mg of zeranol at 2 months or 4.5 months age or at both these ages, and their growth rates were compared with an untreated group. At approximately 8 months age in December the 3 implanted groups were heavier than the control group by 14.6 kg (P less than 0.05), 23.4 kg and 22.1 kg (P less than 0.01). At peak animal weights recorded in March the differences were 18.7 kg (P less than 0.05), 31.3 kg and 31.0 kg (P less than 0.01). In June 1984, following loss of weight by the steers, differences between the implanted groups and the control groups had declined to 7.7 kg (P greater than 0.05), 19.4 kg (P less than 0.01) and 21.1 kg (P less than 0.001), differences similar to those recorded approximately 3 months after implantation. It is concluded that higher weight gains resulted from implanting suckling calves at 4.5 months of age, than by implanting calves at 2 months of age, and that implanting suckling calves twice is unlikely to be any better than implanting them once at 3 to 6 months age. Part of the maximal response can be lost if steers subsequently lose weight.
1983年，三组肉用小公牛犊分别在2月龄、4.5月龄或这两个月龄时植入了36毫克的玉米赤霉醇，并将它们的生长速度与未处理组进行比较。12月，当犊牛大约8月龄时，三个植入组的体重比对照组分别重14.6千克（P<0.05）、23.4千克和22.1千克（P<0.01）。在3月记录的动物体重峰值时，差异分别为18.7千克（P<0.05）、31.3千克和31.0千克（P<0.01）。1984年6月，在公牛体重减轻之后，植入组与对照组之间的差异已降至7.7千克（P>0.05）、19.4千克（P<0.01）和21.1千克（P<0.001），这些差异与植入后约3个月记录的差异相似。研究得出结论，4.5月龄时给哺乳犊牛植入玉米赤霉醇比2月龄时植入能带来更高的体重增加，并且给哺乳犊牛植入两次不太可能比在3至6月龄时植入一次效果更好。如果公牛随后体重减轻，最大反应的一部分可能会丧失。
