Reproductive efficiency and longevity of gilts and sows in group housing and free-farrowing systems versus...

Group housing systems during gestation and free-farrowing pens have recently been implemented in Thailand. This study aimed to investigate how different housing systems, sow parity number and season affect the following outcomes: the percentage of sows returning to oestrus after insemination, farrowing rate, litter traits, piglet preweaning mortality and the age at which sows are removed from the herd. The dataset included 61066 service records from 15666 Landrace × Yorkshire crossbred gilts and sows across three housing systems within a breeding herd. The service records were categorized based on housing systems into three groups: conventional crate (CC, n = 11020), pen gestation with temporary confinement for 35 days post-mating and 10 days post-farrowing (PC, n = 16689) and pen gestation with temporary confinement for 7 days post-mating and complete free-farrowing (PP, n = 33357). The parity numbers of sows were divided into four groups: 0 (n = 11300), 1 (n = 10203), 2 to 4 (n = 25447) and ≥ 5 (n = 14116). The seasons were classified according to farrowing months into three groups: hot (16 Feb to 15 Jun), rainy (15 Jun to 15 Oct) and cool (16 Oct to 15 Feb).

Sows in the CC group had higher farrowing rates and lower remating rates compared with the PC and PP groups (P < 0.001). Litter size was larger in the PP group than in CC and PC groups (P < 0.001), whereas BW was higher in PC group than in PP group (P < 0.05). A significant housing × parity × season interaction influenced most fertility and litter traits, with PP sows showing reduced farrowing rates, increased remating rates and lower BW, particularly in gilts and primiparous sows during the hot and rainy seasons. Weaning performance (NW and WW) was highest in CC sows, especially in gilts across all seasons (P < 0.001). PWM was lower in CC group compared to PC and PP groups (P < 0.001) and influenced by a housing × season interaction (P < 0.001). Sow longevity differed among housing systems, with CC and PC sows remaining in the herd longer and having higher stayability than PP sows (P < 0.001).

Sows in group housing systems experienced lower farrowing rate and higher remating rate. Sows in group housing with free-farrowing system had higher litter size and higher piglet preweaning mortality rate compared to those in the conventional crate system. Sows in the conventional crate system and group housing with temporary confinement post-farrowing remained in the herds longer than sows in group-housed with complete free-farrowing. Hence, there is a need for interventions and husbandry management for balancing animal welfare with reproductive trade-offs in these alternative welfare-friendly systems.