Early prediction of lamb reproductive and growth potential: breed and maternal effects on body and testicular traits

This study examined the variation in body weight, body measurements, and testicular measurements of male lambs from the Cukurova Meat Sheep (CMS) and Awassi breeds, in relation to breed, birth type, dam age, and lamb age. The research included 36 male lambs (18 Awassi and 18 CMS) raised in the Cukurova region. Body weight, body measurements, and testicular measurements were recorded monthly from 1 to 4 months of age, and the effects of breed, birth type, dam age, and lamb age were evaluated with a linear mixed-effects model. The results showed statistically significant differences between breeds in many morphometric traits and some testicular measurements, with CMS lambs generally having higher values. Single-born lambs had higher values in both body and testicular size compared to twin-born lambs. The effect of dam age was limited, while lamb age had a pronounced and significant impact on both body and testicular size. Additionally, positive and generally strong correlations were found among body measurements, testicular measurements, and body weight. In particular, the relationship between scrotal circumference and testicular volume was very strong. In conclusion, early-life measurements of body and testicular traits can be considered reliable indicators for the selection of breeding males, and these traits may be effectively used in sheep breeding programmes.