Effect of lambing season, sex, parity, and litter size on growth performance in lambs—a review

Poor pre-weaning and post-weaning mortality in lambs is common in communal sheep productions due to the use of extensive management practices. Communal sheep producers often lack the resources to address poor performance issues associated with extensive production systems. Non-genetic factors present a potential tool for communal farmers to identify animals prone to poor performance in advance. By using these factors as indicators, farmers can prioritise limited feed additives for lambs at higher risk of poor performance. Key non-genetic factors such as lambing season, sex, parity, and litter size can help identify lamb groups prone to mortality. However, these factors have contrasting effects on pre-weaning and post-weaning lamb performance. Therefore, there is a need to summarise the individual effects of non-genetic factors on lamb performance for the identification of their current trends. Thus, the objective of this review was to assess the effect of lambing season, sex, parity, and litter size mainly on birthweight (0 d BW), weaning weight (90 d BW), and post-weaning weight (180 d BW), as well as pre- weaning (0-90 d BW) and post-weaning (90-180 d BW) average daily gains (ADGs) in lambs.