Sarcoplasmic and myofibrillar proteins and some selected free amino acids in chickens (Gallus gallus domesticus Linn.)

The physiological and biochemical aspect of the skeletal muscle of commercial broilers and native chickens was studied to determine the factors that contribute to the differences in taste of these two breeds. The sarcoplasmic and myofibrillar protein content of breast and thigh muscles of commercial broilers and native chickens raised under range management and confinement were determined at 6 at 16 weeks of age. The experiments were subjected to Analysis of Variance (ANOVA) in Completely Randomized Design (CRD) using SAS. Differences in treatment means were tested for significance using least square means. Age and breed of chickens influenced the sarcoplasmic protein content of muscles. As the broilers get older, the sarcoplasmic protein decreases while as the native chickens get older, sarcoplasmic protein increases. On the other hand, the myofibrillar protein content is significantly affected by the type of management and muscle. The thigh muscle has significantly higher (P greater than 0.01) myofibrillar protein content than the breast muscle. Likewise, native chickens have significantly higher (P greater than 0.01) myofibrillar protein content than broilers. The sarcoplasmic protein extracts showed the presence of a lot of amino acids than the myofibrillar protein extracts. The presence of a few amino acids in the myofibrillar protein extracts was expected since these amino acids are usually mobilized only during muscle activity especially during exercise or stress. While the sarcoplasmic protein serves as a pool of amino acids utilized in time of excessive work to help replenish the degraded amino acids. The meat of native chicken is tougher than broilers due to increase in connective tissue between fascicles which is necessary to give strength during strong muscle contraction. At 16 weeks of age, the breast and thigh muscles of native chickens have significantly higher (P greater than 0.01) myofibrillar protein content than broilers. The increase in myofibrillar protein content in breast and thigh muscles of native chickens is attributed to stress or exercise as these animals search for food. The meat of native chicken still tastes better than the commercial broiler because of its higher myofibrillar protein content