Effects Of Dietary Protein Levels On Production Performance And Nutrient Metabolism Of 7-19 Week Old Bashang Long-tailed Roosters

In order to study the proper protein level of diet for Bashang Long-tail cocks at 7-19week-old,150 healthy Bashang Long-tail cocks at six week-old with similar body weight were randomly divided into five groups,having five replicates per group and six cocks per replicate.The metabolizable energy level in the diets was 11.51MJ/kg.The protein levels in feeds was 14% in Group I,15% in Group II,16% in Group III,17% in Group IV,and18% in Group V,respectively.The adaptation period was one week,and the experimental period was 15 weeks.The growth performance,nutrient metabolic rate,slaughter performance,visceral organ development were determined.The results showed that: 1.The order of body weight for 7-19 weeks was: group V>group IV>group III>group II>group I.The total weight gain and daily weight gain of group III were significantly higher than those of group I and group II(P<0.05).The feed intake of group III was lower than that of group I,group IV and group V,but there was no significant difference among groups(P>0.05).Compared with group I,group II,group IV and group V,the feed gain ratio of group III were the lowest,which were 13.32%,3.21%,1.28% and 0.96% lower,respectively,but there was no significant difference among groups(P>0.05).The shin length of group III in different week-old was the highest,significantly(P<0.05)or extremely significantly(P<0.01)higher than that of group I,significantly higher than that of group II(P<0.05),and there was no significant difference with group IV and group V(P>0.05).The shin circumference of group III was the largest,but there was no significant difference among groups(P>0.05);2.There was a significant positive correlation between energy apparent metabolic rate and dietary protein level(P<0.05),no significant correlation between protein,calcium and phosphorus apparent metabolic rate and dietary protein level(P>0.05);3.At 15 week-old,the slaughter rate and half eviscerated rate of group III were the highest,the chest muscle rate of group III was significantly higher than that of group II and group V(P<0.01),and the leg muscle rate of group III was significantly higher than that of group IV and group V(P<0.05).At 17 week-old,the slaughter rate and half eviscerated rate of group III were significantly higher than those of group I and group II(P<0.05),and there was no significant difference between group III and group IV(P>0.05),but it was significantly lower than that of group V(P<0.05).The total eviscerated rate of group III was significantly higher than that of group IV(P<0.05),and extremely significantly higher than that of group II(P<0.01),and there was no significant difference comparing group I and group V(P>0.05).At 19 week-old,the slaughter rate of group III was significantly higher than that of group I(P<0.05),and extremely significantly higher than that of group II(P<0.01).There was no significant difference comparing group IV and group V(P>0.05).There was no significant difference in half eviscerated rate and full eviscerated rate among the groups(P>0.05);4.There was no significant difference in visceral organ index among groups(P>0.05).The results indicated that at the condition of metabolic energy of 11.51MJ/kg,the level 16% dietary protein can gain the best growth performance.With the increase of dietary protein level,the apparent metabolic rate of energy increased and the apparent metabolic rate of protein decreased.The slaughter performance is the best at 15 week-old.