Fundamental Studies on the Meat Production of the Domestic Fowl : VII. Postnatal Growth of Skeletal Muscle in Some Body Parts of Barred Plymouth Rock Chicken

In the present study, the postnatal growth of skeletal muscle was investigated in the following body parts of the Barred Plymouth Rock chicken. Those were three large parts, namely a body stem’s, a forelimbs’ and a hind legs’ parts. These three parts were further subdivided into nine small parts altogether, that is, the body stem\u27s into a cervical and a dorsocaudal parts, the forelimbs\u27 into an abdominal, a shoulder girdle\u27s, a humeral and an antebrachial parts, the hind legs\u27 into a pelvic, a femoral and a crural parts exactly. Muscle weight of each part was weighed in the left side of the body at fourteen times between zero and thirty-one weeks of age. The results compared the postnatal growth of the skeletal muscle among parts or between sexes were as follows: 1. There were four periods in the postnatal growth of the skeletal muscle between zero and 31 weeks of age. Every period except the fourth was subdivided into two periods, the former and the latter halves. 2. The skeletal muscle developed very rapidly from zero to two weeks of age, particularly in the shoulder girdle’s, humeral and antebrachial parts. 3. Concerning with the percentage of the muscle weight to the live weight, the forelimbs’ part only showed a rapid rate of increase from zero to two weeks of age. Sex-difference of percentage of the muscle weight was led to an apparent increase after sex-maturing in each part. 4. It was confirmed, especially in the male, that the postnatal growth period of the skeletal muscle was composed of two cycles; these cycles have two peaks, the one appeared at the 9-12 weeks of age, and the-ether appeared at the 15-18 or 18-21 weeks of age. 5. The small nine parts were grouped into three classes according to the growth rate between zero and two weeks, one of them was further subdivided into two groups according to the growth after two weeks of age. 6. It was clearly showed that the grading with age of chicken in the market was closely related to the muscle growth or the changes of the muscle weight distribution with age and the difference of it between sexes. The grading of chicken in the market is very reasonable.本研究ではBPR種を用いて体各部位骨格筋の成長を検討した.その際,計測された体各部位は,大割したときの体幹部,前肢部ならびに後肢部の3部位と,さらに,体幹部を頸部と背および尾部に,前肢部を腹部,前肢帯部,上腕部ならびに前腕部に,後肢部を二部,大腿部ならびに下腿部に小割したときの合計9部位である.これらの各部位の骨格筋重量を求め,各部位骨格筋の成長を比較検討した結果の大要は次のとおりであつた. 1. 骨格筋の成長過程に4期が区分され,さらに,第I,IIならびにIII期は前半と後半に分けられた. 2. 第I期(0～2週齢)での骨格筋成蔓には著しいものがあり,特に前肢帯部,上腕部ならびに前腕部等の成長が著しかつた. 3. 骨格筋の生体重比(％)は第I期(0～2週齢)において前肢部のみが著しい増加を示した.また,性成熟期には雌雄間の差が判然となつた. 4. 骨格筋の成長は周期的変化を示し,特に雄において判然としていた. 5. 小割した9部位を第I期(0～2週齢)の骨格筋成長の相違によつて3つのグループに区分し,さらに,その後の成長によつて,その中の1つのグループを2つに区分した. 6. 市場での食鶏の区分と骨格筋成長の変化との間には密接な関係があることがわかり,市場での食鶏区分の正当性を裏付けた