Non-linear growth pattern for body weight, height at withers and body length of Dorper sheep

摘要

There is a dearth of information on age-weight relationship in indigenous and imported sheep breeds raised in tropical region especially in South East Asia. Growth curve parameters estimated from non-linear function are useful to determine optimum market and slaughter weights. The objective of this study was to estimate mature size for body weight, body length and height at withers of Dorper ewes using Brody and Gompertz growth models. Cross-sectional data of body weight, height at withers and body length of 126 Dorper ewes (birth to 6 y of age) were collected and fitted to growth models for estimation of mature size (A), constant of integration (B) and rate of maturing (k). Gompertz model showed higher R2 values for body weight, body length and height at withers (96.4, 99.6 and 99.6, respectively) compared to Brody (87.7, 88.3 and 90.0, respectively). Mature size for body weight, body length and height at withers estimated by Brody model were 62.81+1.833 kg, 67.18+0.5771 cm and 66.90+1.609 cm, respectively, while Gompertz model estimated 60.34±1.486 kg, 67.06+0.551 cm and 66.90+1.596 cm for body weight, body length and height at withers, respectively. Both models estimated negative correlation between parameter A and k for body weight, body length and height at withers, indicating that animals with faster rate of maturing grow faster towards their mature sizes but with smaller sizes compared animals of slower maturing rate.