Group lactation compromises piglet performance and shifts injuries from weaning to lactation

Group lactation systems provide sows with increased movement and the ability to interact with piglets, compared to conventional farrowing crates. The effects of grouping sows during lactation on the welfare and performance of piglets have been studied to a much lesser extent (Li et al. 2012). The nutritional, environmental and social changes that occur during weaning, makes it a stressful period for piglets. This has implications for subsequent post-weaning growth. It was hypothesised that piglets from a group lactation system are better adjusted to weaning and hence would have improved welfare as indicated by growth performance and post-weaning injuries.

Primiparous sows (n = 196) were randomly allocated to one of two treatments; Control sows (n = 49) were housed in traditional farrowing crates for the duration of lactation, and Grouped sows (n = 147) were housed in traditional farrowing crates until 14 days before weaning, at which point they were mixed into groups of three with litters until weaning. On d –14, –12, –1, +1, +7, +14 and +30 relative to weaning, piglets were weighed and assessed for injury score (with the exception of d +14) using a modified injury score (Widowski et al. 2003), which consisted of a four-point scale for scratches around the head and ears of each piglet. Statistical analyses were conducted using a generalised linear mixed model (Proc MIXED) in SAS 9.1 (SAS Institute Inc., Cary, NC, USA) with grouped lactation sows treated as a group. Data are expressed as least-squares means ± s.e.m.

Grouped piglets were lighter following the grouping event. On the day before weaning, Control piglets weighed 0.56 kg more that Grouped piglets (7.2 kg v. 6.6 kg; P < 0.05; Fig. 1) and d 30 post-weaning Grouped piglets were still lighter (by 0.77 kg) but not significantly. Variation in grouped piglet weight increased with age to d +14, but decreased in Control piglets during the same period. Post-mixing on d –12 relative to weaning the number of injuries sustained by grouped piglets was double that of control piglets (Fig. 2). By d +7 post weaning, injuries were highest in control piglets.

Fig. 1.  Pre- and post-weaning piglet growth from control piglets and piglets grouped for the last 14 days of lactation. Day 0 represents weaning.

Fig. 2.  Pre- and post-weaning injury scores from control and piglets grouped for the last 14 days of lactation. Day 0 represents weaning.

Whether piglets are mixed in lactation or after weaning, they sustain injuries most likely attributed to fighting behaviour. This study could not determine whether these injuries were related to competition at the udder or dyadic agonistic interactions. Grouped lactation slows the growth performance of piglets which is not compensated for post weaning.