Estimation of growth curve parameters of Dorper x Tumele sheep under semi-intensive management system using nonlinear models

This study aimed to determine the suitability of the Brody, Gompertz, Logistic, Monomolecular, Negative Exponential, and Von Bertalanffy nonlinear models to the growth curves of Dorper cross with Tumele indigenous Ethiopian sheep breed. The body weight record from birth to yearling was used to drive the growth curve. For different groups of sheep, such as blood levels (50% and 75% Dorper blood level), sex (female and male), and types of birth (single and twin), all functions were compared to estimate the growth curve parameters. In this study, four goodness-of-fit criteria were used to select the best-fitting model, including the Bayesian Information Criterion (BIC), Akaike Information Criterion (AIC), Root of Mean Square Error (RMSE), and coefficient of determination (R 2 ). This study showed that for Dorper x Tumele sheep, the model Brody was the best fit by considering lower BIC, AIC, and RMSE and higher R 2 values. In this model estimation, female sheep had a lower estimated mature weight compared to male sheep, but there was no difference in the initial animal weight and maturation rate between the sexes. However, sheep with 75% Dorper blood level had almost similar asymptotic (mature) weights and initial animal weights compared to those with 50% Dorper blood level. At maturity, single-born lambs were only 1.5% heavier than twins. As a result, applying Brody to describe the weight gain, mature weight, maturing rate, and body weight of animals at any point of the growth trajectory could be important. These findings may help producers and experts perform better feeding, breeding, and overall husbandry practices for this crossbred sheep.