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.
本実験では雄鶏の去勢が体格部位骨格筋および個々の骨格筋の発育に及ぼす影響について研究した.供試鶏としては New Hampshire (NH)種と Barred Piymouth Rock (BPR)種の雄鶏と去勢鶏,それにBPRの去勢鶏に testosterone propionate (TP)を26週齢時から31週齢時まで投与したTP処理鶏を用いた.それぞれ計量した生体重,体格部位骨格筋および個々の骨格筋について,雄鶏と去勢鶏間では20,30,31週齢時に,去勢鶏とTP処理期間では31週齢時に比較検討を行った.その大要は次のとおりであった.1)去勢鶏の生体重の変動は両品種とも雄鶏と同じであった.しかし,BPRのTP処理鶏でのTP投与期間中の増体量は雄鶏や去勢鶏より有意に大きかった.2)去勢は体格部位骨格筋の発育に著しい影響を及ぼした.すなわち,30-31週齢時における去勢鶏の頸部,背および尾部,寛部,大腿部および下腿部骨格筋重量は両品種とも雄鶏より有意に小さく,特に大腿部で顕著であった.BPR去勢鶏へのTPの投与は去勢により発育の劣った骨格筋部位の発育の回復を引き起こした.3)去勢は個々の骨格筋の発育にも著しい影響を及ぼした.すなわち,30-31週齢時における去勢鶏の個々の骨格筋重量は後肢を構成する縫工筋,大腿二頭筋,半腱様筋,半膜様筋および大腿四頭筋等で雄鶏より有意に小さく,特に縫工筋で顕著であった.BPRの去勢鶏にTPを投与すると去勢によって発育の劣った個々の骨格筋の発育の回復がみられた.以上のことから,雄鶏の去勢は特に後肢骨格筋の著しい重量低下をもたらしたが,それは精巣Androgenの欠如による特定骨格筋の発育の遅延に起因するものと思われる.