Consistency is key: interactions of current and previous farrowing system on litter size and piglet mortality.

Global interest in alternative indoor farrowing systems is increasing, leading to a growing number of farms utilising such systems alongside standard crates. There is evidence that interchanging sows between different farrowing systems affects maternal behaviour, whilst the subsequent effect of this on piglet mortality is unknown. The current study hypothesised that second parity piglet mortality would be higher if a sow farrowed in a different farrowing system to that of her first parity. Retrospective farm performance records were used from 753 sows during their first and second parities. Sows farrowed in either standard crates (crates), temporary crates (360s) or straw-bedded pens (pens), with mortality recorded as occurring either pre- or post-processing. Inter- and intra-parity sow consistency in performance were also investigated. Overall, total piglet mortality reduced from the first to the second parity, being significantly higher in the crates and higher in the 360s during the first or second parity, respectively. In the second parity, an interaction of the current and previous farrowing systems resulted in the lowest incidence of crushing for sows housed in the same system as their first parity for the crates and pens, but not the 360s. Post-processing mortality was significantly higher in the crates if a sow previously farrowed in the 360s and vice versa. Sows which previously farrowed in a pen had a significantly larger litter size and lower pre-processing mortality from crushing in their second parity than sows previously housed in the crates or the 360s. No inter-parity consistency of sow performance was found, whilst intra-parity consistency was found in the first but not second parity. In conclusion, returning sows to the same farrowing system appears to reduce piglet mortality, whilst farrowing in a pen during the first parity significantly increased second parity litter size without increasing piglet mortality.