ผลของรูปแบบการเลี้ยงต่อคุณภาพซาก ลักษณะทางกายภาพ และองค์ประกอบทางเคมีของเนื้อไก่เบตง

Abstract

The objectives of this study were to investigate the effect of rearing system on carcass quality, physical properties and chemical composition of Betong chicken meat. Three hundred and sixty 1-day-old chick were randomly allocated to 3 treatment: (1) indoor treatment, housing in an indoor pen (4 birds/m3), (2) chickens were reared in the house with access to the courtyard outside the house (1 bird/m2) and (3) chickens were reared in the house with access to the courtyard outside the house (2 bird/m3), during 5 week of age to slaughter. Each treatment was represented by 4 replications containing 30 birds each. All birds were provided with the same diet and were reared for 24 weeks. This experiment was conducted with completely randomized design (CRD). At 16 and 24 weeks old, sixteen birds of each rearing system were randomly selected and slaughtered for carcass characteristics, physical properties and chemical composition. From the study, rearing system had no significant effect on live weight, warm carcass and chill carcass weight, retail cut and abdominal fat percentage (P>0.05). In terms of carcass characteristics, at 16 weeks the males chicken in semi-free range had higher dressing percentage and yellowness value in thigh muscle than the chicken in the indoor treatment, while the redness value had significantly higher (P<0.05) in the female chickens. In addition, the different rearing system caused higher yellowness value of thigh skin of the female aged 24 weeks old (P<0.05). Nevertheless, rearing system did not show any effect on pH, drip loss, cooking loss and shear force values of breast and thigh muscles (P>0.05). For chemical composition, it was observed that rearing system did not affect moisture, protein, ash, collagen and cholesterol contents (P>0.05). However, at the aged at 24 weeks old, it was indicated that the females had lower fat content of thigh meat and eicosapentaenoic acid (C20:5n3) than the males. In addition, chickens reared under semi- free range had C20:5n3 higher than those reared under the indoor system (P<0.05). Furthermore, the arachidonic acid (C20:4n6) in breast meat from semi-free system was lower than the indoor system (P<0.05). Rearing system did not show any significant difference in the saturated fatty acid, monounsaturated and polyunsaturated fatty acids of both breast and thigh meats (P>0.05). When determing the effect of age or sex on the physiochemical quality of meat, it was found that live weight, dressing percentage, shear value, collagen, fat and n-3 fatty acids contents were increased (P<0.05), while the yellowness value of the skin and meat decreased when the age of chicken increased. Live weight, dressing percentage, shear value, and redness score of the males were higher than the female chickens (P<0.05). Males at 16 weeks of age had similar live weight, chemical fat and n-3 fatty acid contents with the 24 weeks old females. Nevertheless, the ratio of n-6 to n-3 fatty acids in meat was significantly decreased when the age of chicken increased.