Requirement Of Dietary Protein Of Lueyang Black-boned Chicken During The Growing Period

Three experiments were conducted in the present study to evaluate the effects ofdifferent levels of dietary CP on growth performance, carcass characteristics, serumbiochemical indexes, immunity and antioxidation capacity of Lueyang black-boned chickenduring the growing period in order to determine the appropriate CP requirement of them.Then the results can be used as theoretical basis to formulate the raising standard of Lueyangblack-boned chicken. And the production of Lueyang black-boned chicken can also beguided.Trial1was undertaken to assess dietary CP concentration for optimum growthperformance, carcass characteristics and serum biochemical indexes of Lueyang black-bonedchicken. A total of600forty two-day-old Lueyang black-boned chicks were randomlyassigned to five treatments, each treatment contained6replicate pens with10males and10females. The birds fed experimental diets with the same metabolizable energy (12.34MJKg-1) and different levels of protein concentration of12.39%,14.20%,16.60%,18.06%and20.15%from7to12weeks of age respectively. On day of84, weight gain, feed intake,feed:gain were measured, and2chickens (1male and1female) selected randomly from eachpen were slaughtered to evaluate the carcass characteristics and serum selected biochemicalindexes. Dietary CP concentration did not have any significant influence on feed intake(P>0.05). The birds fed the diet with18.06%or16.60%CP concentration exhibited greater(P<0.05) in growth rate, feed conversion rate, proportional breast weight and albuminconcentration in serum than that of those fed other dietary CP concentrations. According tothe results of regression analysis, the CP requirement of Lueyang black-boned chicken from7to12weeks of age for optimal weight gain or feed:gain was17.52%and17.18%,respectively.Trial2was undertaken to assess the effect of dietary CP concentration on growthperformance, carcass characteristics and serum biochemical indexes of Lueyang black-boned chicken. A total of600eighty five-day-old Lueyang black-boned chicks were randomlyassigned to five treatments, each treatment contained6replicate pens with10males and10females. The birds fed experimental diets with the same metabolizable energy (12.34MJ Kg-1)and different levels of protein concentration of12.39%,14.20%,16.60%,18.06%and20.15%from13to18weeks of age respectively. Growth rate, feed intake, feed:gain were measured atday105and126. And on day126,2chickens (1male and1female) close to the averageweight of all birds in each treatment were selected from each pen and slaughtered to evaluatethe carcass characteristics and serum selected biochemical indexes. The results were as follow:(1)13~15weeks: During this period, it was clear that dietary CP did have significantinfluence on feed intake, growth rate and feed:gain in male chickens (P<0.05). There was nosignificant difference in growth rate (P>0.05), but the effect of CP level was significant forthe feed intake and feed:gain in female birds (P<0.05).(2)13~18weeks: The CP level had nodifferential effect on growth rate in male chickens (P>0.05), while feed intake and feed:gainshowed a significant downward trend as the CP level increases (P<0.05). Dietary CP did nothave any significant influence on growth rate and feed:gain in female birds(P>0.05)，while CPlevel significantly affected on the feed intake and uric acid concentration in serum (P<0.05).Based on comprehensive effects of dietary CP level on growth performance, carcasscharacteristics and biochemical indexes in this experiment with a similar ME value (12.34MJkg-1), the present results suggest that the optimal CP requirement of Lueyang black-bonedchicken from13to15weeks of age was16.60%to18.06%. And the optimal CP requirementof Lueyang black-boned chicken from13to18weeks of age was16.60%to18.06%.Trial3was undertaken to assess the effect of dietary CP concentration on immunity andantioxidation capacity of Lueyang black-boned chicken. A total of180forty three-day-oldLueyang black-boned chicks were randomly assigned to three treatments, each treatmentcontained5replicate pens with12chicks. The birds fed experimental diets with differentlevels of protein concentration of12.39%,16.60%and20.15%from7to12weeks of agerespectively. On day56,70and84,1chicken close to the average weight of all birds in eachtreatment were selected from each pen and slaughtered to evaluate the serum immunity indexand serum and hepatic antioxidation index. The results were as follow:(1) Dietary CPconcentration did not have any significant influence on serum immunity index from7to12weeks of age (P>0.05).(2) The birds fed the diet with16.60%and20.15%CP concentrationexhibited greater (P<0.05) in T-AOC concentration in serum on day56and SODconcentration in serum on day70than that of those fed12.39%CP concentrations. And MDAconcentration in serum on day84showed a significant downward trend as the CP levelincreases (P<0.05).(3) CAT concentration in hepatic showed a significant rise as the CP level increases on day56and70, but it was not significant on day84. In conclusion, theantioxidation capacity of Lueyang black-boned chickens showed an enhanced trend with theincrease of CP level.