雄鶏

Effects of castration on the growth of muscles in different body parts were investigated in this study in cocks. Cocks and capons of New Hampshire (NH), Barred Plymouth Rock (BPR) and capons of BPR treated with testosterone propionate (TP) from 26 to 31 weeks of age were used. Body weights, muscle weights in different body parts and individual muscle weights were compared among the experimental groups at 20, 30 and 31 weeks of age. The results obtained were as follows: 1) There was little difference in body weitht between cocks and capons in NH and BPR breeds during experimental periods However, body weight gain in TP treated capons was significantly larger than those in cocks and capons during the period of TP administration. 2) Growth retardation of muscles was observed in cervical, dorso-caudal, pelvic, femoral and crural parts after castration. Muscle weights of these parts in capons were significantly smaller than those of the corresponding parts in cocks at 30-31 weeks of age. The most obvious retardation of muscle growth was seen in femoral part in capons. As the result of TP administration to capons, muscle weights of these parts were recovered from the weights in capons to those in cocks. 3) Castration had also a remarkable effect on the growth of the individual muscles such as M. sartorius, M. biceps femoris, M. semitendinosus, M. semimembranosus and M. quadriceps femoris. Weights of these muscles in capons were significantly smaller than those in cocks at 30-31 weeks of age. The most conspicuous retardation was seen in M. sartorius in capons. As the result of TP administration to capons, these individual muscle weithts were recovered from the weights in capons to those in cocks. In conclusion, castration had a remarkable effect on the growth of muscle, with the conspicuous depression of the growth of hindleg muscle in particular. It seems that this was due to the retardation of special muscle growth as the result of the lack of androgen secretion from testis.