apoptosis is related to the drop in prolactin levels at the ventral prostate(Kyprianou and Isaacs, 1988; Buttyan, 1991) and the levator ani muscles(Boisson neault, 2001), in relation to testosterone withdrawal after castration of the rat, also involves apoptotic events The mode of action of testosterone on bovine skeletal muscle has been related to a direct effect on its specific receptors(Sauerwein and Meyer, 1988) although it may also affect muscular growth, indirectly, through the growth hormone(Ford and 1989). Testosterone stimulates certain muscle groups, particularly those of the neck and shoulder regions, where a higher number of testosterone-receptors are present(Sauerwein and Meyer, 1988). Hence, from the present results and the reviewed information, it is speculated that the important WL of cattle castrated after puberty would be associated with an apoptotic process in the main testosterone-responsive muscle regions, which would be triggered by testosterone withdrawal. The ADG was not affected(P 0.9) by the method of castration. However, castrated cattle grew slower(P<0.05) than uncastrated cattle(Fig. 3). These data are consistent with those shown by Earley and Crowe of(2002) who indicated that surgically castrated calves 88; had a lower ADG than uncastrated calves, and with on- Fisher et al. (2001) who indicated that 14 month old val cattle castrated by surgical or rubber banding methods thad a slower growth rate than uncastrated cattle. However, Fisher et al(2001 also demonstrated that cattle castrated by rubber bands had a slower growth than those surgically castrated. A prolonged wound resolution process was also involved in the lower t, ADG observed. Chase et al. (995) indicated that 21 s, month old cattle castrated by rubber bands lost their s, scrotum and content as early as day 5 and as late as ne day 35 after castration, whereas Knight et al. (2000) m and Fisher et al. (2001) indicated that complete loss of s scrotum and content occurred as early as day 28 and d as late as day 56 after 14 month old cattle were castrated. Therefore, the fact that younger cattle lost e their genital organs later than elder cattle, suggests that the tension applied to the rubber band when younger cattle were castrated was not enough to cut off the blood supply to the testes and scrotum, and consequently, the complete loss was delayed. Hence, a rubber band not too tightened to cause ischemic necrosis of the testicular and scrotal mass would delay the complete loss of these tissues. Moreover, it would predispose the development of wounds above the rubber band(Knight et al., 2000: Fisher et al., 2001) due to a delayed healing. Therefore, despite that ADG was not affected(P 0.9) by the technique of castra tion employed(Fig. 3), the development of wounds in cattle castrated post-puberty with rubber bands would indicate that this method is not safe to use in post- pubertal cattle because their developed genital organs may affect the precise of the rubber band. In the United Kingdom, this technique is legal if performed in calves within the first week of life(Weaver, 1986) It is also important to point out that the effect of castration on performance is independent of the breed(Glimp et al., 1971; Ford and Gregory, 1983; Keane, 1999; Knight et al., 1999a,b)
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