Reproductive issues in welfare-friendly housing systems in pig husbandry: a review.

In Europe, housing conditions of sows are currently changing, related with a larger emphasis on pig welfare. As a result, sows are and will be less kept in crates, but more so in loose housing systems (farrowing, lactation) and group housing systems (pregnancy, lactation, weaning-to-oestrus interval). These changes in housing conditions may affect reproductive functioning of the sows. Group housing of sows may decrease farrowing rate and litter size when stress levels rise or when feed intake in early pregnancy is not fully secured. Loose housing during farrowing results in an improved farrowing process, but may increase piglet mortality by crushing during early lactation. Further, group housing during lactation may increase the risk of lactational oestrus. Thus, new - welfare friendly - housing systems require increased attention to management to ensure optimal reproductive performance.