Comparative analysis of growth and development characteristics of two Dezhou donkey strains

Dezhou donkey, divided into Wutou and Sanfen strains, is one of the largest local breeds in China, famous for its tall and muscular body. Information regarding the growth and development indicators in Dezhou donkeys is limited. The present study explored the growth and development pattern of body weight (BW) and body measurements in the growing Dezhou breed donkey. The linear and non-linear models fitted the growth curve for Dezhou donkeys, and the stepwise regression equations for estimating BW were also developed. Both the birth weight and body height (BH) of Wutou were greater than Sanfen donkey (P < 0.05). With the age and BW increasing, the body measurements, including BH, body length (BL), thoracic girth (TG) and cannon bone girth (CG), increased accordingly. The Brody model was selected as the best model for fitting the growth curve with the highest R2 (0.991) and lowest AIC (2418.7) and RMSE (5.12). The parameter 'k' of the Sanfen donkey was lower in comparison with the Wutou donkey, suggesting that Wutou achieved asymptotic weight earlier than the Sanfen donkey. The stepwise regression analysis was conducted to obtain the best prediction equations for BW of Dezhou donkeys from body measurements: 1.34 × TG + 0.59 × BH + 0.45 × BL + 2.45 × CG –170.3 (R2 = 0.962, P < 0.01). In summary, the present study provided evidence that the growth rate of the Wutou donkey is faster than that of Sanfen, and both of them fitted the Brody growth curve from birth time to 18-month-old.