Lambing Season and Birth Type Influence on the Relationship Between Ewe Early Growth and Lifetime Lamb Production in Rahmani Sheep

Lifetime lamb production is a crucial measure of ewe efficiency and overall flock profitability. Therefore, the study investigated the relationship between early ewes’ growth traits (birth weight, weaning weight, yearling weight) and lifetime lamb production in Rahmani ewes across lambing seasons and birth types. This study meticulously examined a substantial dataset comprising 2371 records from 880 Rahmani ewes (105 sires and 495 dams). Results revealed significant variability in both growth and reproductive performance. Higher birth weight (>3.5 kg) generally improved further lifetime lamb production, particularly in single-bearing ewes and warmer seasons, while weaning weight showed seasonal-dependent effects. Interestingly, higher yearling weight (≥31 kg) was significantly associated with higher productivity in multiple-bearing ewes. While weaning and yearling weights have little significant impact on the lifetime lamb productivity of single-born ewes, higher weaning and yearling weights are positively associated with better lifetime lamb production, particularly prolificacy traits for ewes born in multiple litters. Genetic analyses indicated moderate heritability for both trait categories and positive genetic correlations between early growth and lifetime reproductive success. Estimated breeding values demonstrated substantial genetic diversity within the flock. Collectively, these findings underscore the complex interplay between early growth, lambing season, and lifetime productivity in Rahmani ewes. They provide valuable insights for developing effective breeding strategies focused on enhancing both growth and reproductive efficiency to improve the economic sustainability of Rahmani sheep production in Egypt.