In this study, the forelimbs' muscle, one of the important parts of chicken body for meat production, was compared quantitatively with its weight among various breeds and sexes. Males and females of Rhode Island Red (RIR), Barred Plymouth Rock (BPR), White Leghorn (WL) and males of White Cornish (WC) were used. The experimental period was from 2 to 18-19 weeks of age. Weighing of skeletal muscle was done in the forelimbs' part and its four different subparts (shoulder girdle, brachium, antebrachium and abdomen). Regression equations of males and females of each breed were calculated between the muscle weight of these parts and live weight or total muscle weight. And these equations were applied to the study of ability of meat production. The results were as follows: Specific individual ability of meat production in the forelimbs' part and its four subparts was observed among all breeds and sexes. This individual ability was controlled by two factors: one was the rate of increase of the live weight, and the other was the rate of increase of the individual muscle percentage weight against the live weight. In males, it was supposed the ability of meat production of the forelimbs' part was best in WC among all breeds. Although the percentage weight of forelimbs' muscle of WL exhibited about the same high value as that of WC until 2kg of live weight, it was not always said that WL was a good meat producer in the forelimbs' part, for its rate of increase of live weight was smallest of all breeds. RIR and BPR showed the smallest rates of increase of the muscle percentage weight. But these breeds seemed to be better meat producers in the forelimbs' part than WL because of those larger rates of increase of live weight. In females, the results were as same as those of males among all breeds. Between sexes, the percentage weight of forelimbs' muscle of females increased more rapidly than that of males in all breeds. The percentage weight of forelimbs' muscle to total muscle weight did not change in WL females, and decreased in WL males and all other breeds. This suggests that the ability of meat production of forelimbs' part falls behind that of other parts in the body. When forelimb was divided into four subparts, the ability of meat production of each subpart was also discussed. The percentage weight of shoulder girdle's muscle to live weight increased conspicuously in WC and WL, but that of brachial and antebrachial muscles was more increased in RIR than in other breeds. The percentage weight of shoulder girdle's muscle to total muscle weight increased in WL females and did not change in males of WC and WL and in females of BPR and RIR. It seemed that shoulder girdle's muscle developed slightly larger than other subparts' in forelimb.
鶏の前肢部は重要な精肉生産部位である.この前肢部とその中に4部位を細分し,それぞれの部位の骨格筋成長に関して,品種および雌雄間の差異を検討した.使用した品種はWhite Cornish種(WC)雄, Rhode Island Red種(RIR)雌雄, Barred Plymouth Rock種(BPR)雌雄およびWhite Leghorn種(WL)雌雄鶏であつた.鶏体の前肢部およびその中の4部位での骨格筋重量を2週齢から18~19週齢まで計測し,これらと生体重および総筋肉量の間に回帰方程式を求めた.この回帰方程式に基づき,各品種および雌雄間で前肢部の産肉能力を比較検討した.その結果,前肢部とその中の4部位の産肉能力は品種および雌雄に特有の筋肉量の生体重比と生体重の増加速度によつて規定された.雄ではWCの前肢部で産肉能力が最も高かつた.WLの前肢部は筋肉量の生体重比でWCに次いで高い曲線を示したが,生体重の発育で著しく劣り,必ずしも産肉能力が高いとはいえなかつた.RIRやBPRの前肢部は最も低い生体重比曲線を示したが,生体重の発育はWLより勝り,また産肉能力も勝るものと思われた.雌の品種間での傾向も雄と同様であつた.雌雄間では雌の方が前肢部筋肉量で大きな生体重比を示した,前肢部筋肉量が総筋肉量に占める割合はWL雌を除き,他はすべて総筋肉量の増加とともに減少の傾向を示し,前肢部骨格筋の発育がその他の部位にやや劣ることを示唆した.WL雌ではほとんど変化しなかつた.小割した4部位の中では,WC,WLの前肢帯部筋肉量の生体重比が,RIRの上腕部筋肉量,前腕部筋肉量の生体重比がそれぞれ他の品種のそれらより大きかつた.また,前肢帯部筋肉量の総筋肉量比はWL雌で増加の傾向を示し,WC雄,WL雄,BPR雌およびRIR雌でほとんど変化しなかつた.このことは前述の前肢部筋肉量の結果と比較したとき,前肢帯部筋肉量の増加率が前肢部の中の他部位筋肉量のそれより少し勝ることを示唆するものであろう.