The impact of parity, litter size and birth weight variations within a litter on piglet pre-weaning performance

Sows are selected for their prolificacy. Therefore, assessing difficulties that can be associated with large litters is crucial. This review aims to highlight the factors that can affect reproductive performance such as breed, parity, litter size, environment, and nutrition. Understanding these factors can help producers make informed decisions about sow management and other aspects. Higher within-litter variation is the result of a high number of piglets born. It has been determined that large litter sizes pose a risk to animal welfare in the pig industry. Moreover, large litters bring more piglets with low birth weight leading to high pre-weaning losses. Lighter littermates struggle to get enough colostrum due to the competition with heavy littermates, which lowers their chances of survival causing high mortality. Larger litters may cause greater stress and discomfort of the sow. Therefore, applying stress-free environment and treating the sow with anti-inflammatory compounds may enhance the sow performance and consequent survival of piglets. The litter size is positively correlated with the variation in birth weight within a litter, while the average weight at birth is negatively related to litter size. Producers should therefore focus on potential management strategies that can improve piglet performance, survival and welfare such as proper supervision and adequate colostrum intake. This review highlights the historical development of the pig industry and literature on the variation in piglet weight at birth within a litter, factors influencing weight at birth, and the potential effects on the piglet performance before weaning. Also, the difficulties amongst large litters and possible strategies for managing survival in large litters were also reviewed.