Effect Of Dietary Protein Levels On Production Performance, Slaughter Trait And Partial Meat Quality In Chickens

Shaobai chickens at the age of 4 weeks were randomly divided into group 1, 2, 3,and 4, and each group was 80 chickens which had 40 male and 40 female chickens. Thechickens of group 1, 2, 3 and 4 were fed the diets which protein levels were 20％,18.5％, 17.0％and 15.5％respectively at 4～7 weeks of age, and the diets which proteinlevels were 18％, 17％,16％and 14％respectively at 8～10 weeks of age. Productionperformance, slaughter traits, inosinic acid content and content of breast muscle fat atdifferent dietary protein levels were measured. The results showed that:1. There were no significant differences of body weights among group 1, 2 and 3chickens at 10 weeks of age (P＞0.05). Body weights of group 4 were no significantdifference than that of group 3 (P＞0.05), and extremely significant higher than that ofgroup 1 and 2 (P＜0.01).2. The growth law of Shaobai chickens was studied using logistic curve, and thecoefficient of determination of the logistic model (R~2) was 0.9974. The result indicatedthe logistic curve could fit Shaobai chickens very well.3. The weights of dressed chickens of group 1, 2 and 3 were extremely significanthigher than that of group 4 at 10 weeks of age(P＜0.01). The weights of dressed chickensof group 1 were significant higher than that of group 2 and3 at 10 weeks of age(P＜0.05).There was significant difference of half-eviscerated weight between group 1 and group 4(P＜0.05). There were significant difference of eviscerated weight between groupl andgroup 3, 4 (P＜0.01). Eviscerated weight of group 2 was significant difference than thatof group 4 (P＜0.05). There were no significant differences of weights of breast muscleamong group 1, 2, 3 and 4 (P＞0.05). Weights of leg muscle of group 1 were significantdifferences than that of group 2, 3 (P＜0.05), and extremely significant difference thanthat of group 4 (P＜0.01). Skin fat thickness of group 2 was significant difference than that of group3 (P＜0.05), and extremely significant difference than that of group 4(P＜0.01). Skin fat thickness of group 1 was extremely significant difference than thatof group 3 and 4 (P＜0.01). There were no significant differences of weights ofabdominal fat and width of breast muscle fat strip among four groups (P＞0.05).4. There were extremely significant correlation among live body weight, weight ofdressed chicken, half-eviscerated weight, eviscerated weight, breast muscle weight andleg muscle weight of Shaobai chicken at 10 weeks of age, and there were no significantcorrelation between those characters and content of breast muscle, skin fat thickness(P＞0.05). The correlations of slaughter traits in male group was different than that offemale group, which were smaller than that of whole group.5. Content of breast muscle fat in group 1 was significant difference than that ingroup 3 and 4 (P＜0.05) at 10 weeks of age. There was no significant difference betweencontent of breast muscle fat in male and that in female (P＞0.05). Content of breastmuscle fat in group 3 was the highest among four groups. There were no significantdifferences of inosinic acid content among four groups(P＞0.05). The result reflected thatdietary protein levels did not effect on inosinic acid content.