Influence of altitude on growth curves in Tibetan chicken and its hybrid

Tibetan chicken is a precious resource in Qinghai-Tibet Plateau.In order to study its growth rhythm and het-erosis of its hybrid,three groups,Tibetan chicken(T),Dwarf Recessive White(D) and Tibetan×Dwarf Recessive White(TD) were reared under the same management at low-and high-altitudes.Measurements were made on body weight and shank lenght,and growth curves were fitted using Richards model.The results showed that the model fitted well with the chickens’growth courses in weight and shank withR2of more than0.99.The high-altitude might retard the growth of chickens,with decreases in inflection point values,final values and maximal growth rates and prolonga-tion of inflection point time.The final weight,inflection point weight,and maximal growth rates of Tibet chicken were1 008.3g,477.9g and11.69g receptively at low-altitude,and525.3g,229.5g,and5.12g at high-altitude.This showed a decline of47.9%,52.0%,and56.8% at the high-altitude;the degree of influence of altitude were less than that of Dwarf Recessive White.The TD had high heterosis in weight gain,and at high-altitude the heterosis of final weight,inflection point weight,and maximal growth rates were59.5%,56.8% and52.3% respectively.Therefore,the Tibetan×Dwarf Recessive White cross was good for improving the Tibetan Chicken.