Study On The Growth And Development Of Yangyuan Donkey

In order to study the growth and development law of Yangyuan donkey,the body size index(body height,body length,chest circumference,tube circumference)and body weight of 417 individuals of Yangyuan donkey were measured,and their characteristics in different growth and development stages were analyzed.The results showed that the period before weaning of Yangyuan donkey was the period of rapid growth of body weight.By the age of 6 months,the average body weight of Yangyuan donkey had reached 80.1kg,which was 45%of that of adult donkey 28%,with an average monthly gain of 7.82kg.Although the growth trend of body size indexes of Yangyuan donkeys in 6-42 months old is still on the rise,the growth rate is slower than that before 6 months old,and the body size(body height,body length,chest circumference and tube circumference)no longer increases to 33 months old;the growth trend of body size indexes is similar to that of body weight;417Yangyuan donkeys measured are in a balanced growth and development,and the body weight and body size indexes are distributed around the fitting curve Through the analysis of the correlation between body weight and body size,it can be found that body length,body height,chest circumference and body weight have a positive correlation,with chest circumference having the highest correlation,followed by body length;the absolute growth and relative growth trend of Yangyuan donkey’s body weight and body size index are consistent,with a trend of rapid decline to slow growth,and the turning point is around 6 months old.Through the establishment of Gompertz,logistic and bretalanfy models,the growth fitting degree of logistic model is the highest,which is 0.9964,indicating that the fitting degree of logistic model is higher than that of Gompertz and bretalanfy model.At the same time,according to the positive correlation between body weight and body size,the body weight was estimated by chest circumference and body length,and two weight estimation formulas were calculated:Formula 1:body weight=247.92×chest circumference(m)-154.67;formula 2:body weight=65.85×[chest circumference]~2(m)×body length(m)+21.68.There was no significant difference between the two formulas and the measured weight.