Group-lactation housing from 7 or 14 days post-partum: effects on piglet behaviour

Group-lactation housing may improve sow and piglet welfare by increasing opportunities to move about and express social and maternal behaviours (van Nieuwamerongen et al. 2014). This study tested the hypothesis that piglets reared in multi-litter groups from 7 or 14 days of age would display more positive and less negative behaviours during lactation, and deliver less aggression when mixed post-weaning, compared to piglets reared in standard farrowing crates.

The litters (n = 1551 piglets) of 112 sows (Large White × Landrace, PrimeGro™ Genetics, Corowa, NSW, Australia) were allocated to one of three treatments over four time replicates: 1) Group lactation (GL) from 7 days post partum (GL₇, n = 48 litters), 2) GL from 14 days post partum (GL₁₄, n = 48 litters), or (3) Farrowing crate (FC; n = 16 litters). All dams farrowed in standard farrowing crates, where FC litters remained (with their dams) until weaning. GL₇ and GL₁₄ litters were transferred (with their dams) from farrowing crates to GL pens (one pen of five sows at 8.4 m²/sow and one pen of seven sows at 8.1 m²/sow, per treatment and replicate) at 7 and 14 days post partum, respectively. All treatments were weaned at 28 days post partum. Treatments were balanced for sow parity, weight and litter size, and there were no treatment differences in litter weight and sex ratio, or variation in these variables. Four focal piglets (one average-sized male and one average-sized female from a high and a low parity dam) per GL pen, and two focal piglets per FC (selected as per GL piglets), were video recorded from 0700 to1700 h on the day after mixing (D2) and 2 days before weaning (pre-weaning, PW). Of the four FC litters per replicate, two were video recorded on the same days as GL₇ (FC₇) and the other two recorded on the same days as GL₁₄ (FC₁₄). Piglet time-budgets were observed using point sampling with 5 min intervals. Behaviours were analysed with LMM and GLMM models (SPSS v23.0, IBM, Armonk, NY, USA), with the main and interactive effects of housing (GL v. FC), litter age at mixing (7 v. 14 days) and observation day (D2, PW), as repeated-measures and controlling for pen and replicate as random factors (Table 1). Effects of GL₁₄, GL₇ and FC treatments on aggression following mixing with unfamiliar (ratio 50 : 50) pigs post-weaning was also analysed for one replicate (five pens/treatment, 12 pigs/pen).

Table 1.  Percent of observations piglets recorded performing behaviours, by housing (GL, FC), age of GL litter at mixing (7 or 14 days) and observation day (d 2 post-mixing, D2; 2 days pre-weaning, PW)

Time spent suckling declined over lactation for all housing treatments. GL piglets suckled mostly from their dam at d 2 post-mixing, but mostly from other dams at d 26. The higher incidence of potentially harmful manipulations (manipulating ears, belly/tail) in FC compared to GL treatments at d 26 requires further investigation. No other piglet behaviours were affected by lactation housing. Post-weaning, FC pigs delivered 57 to 72% more single bites/knocks, and engaged in 43% more fights post weaning than GL pigs. The means for GL₇, GL₁₄ and FC piglets were, respectively, 17.0, 11.2 and 39.8 bites/knocks per pig (P < 0.001) and 1.29, 1.48 and 2.45 fights per pig (P = 0.006). This suggests that group-lactation systems can reduce piglet’s aggression post-weaning.