Influence of pig weight classification at cross-fostering on the performance of the primiparous sow and the adopted litter

The objective of this study was to evaluate the effects of piglet weight and variation in weight at cross-fostering on piglet and sow performance. Primiparous sows were allocated in three groups: group A (n=31)-litters with 14 Light piglets (1.0-1.2 kg); group B (n=32)-litters with seven Light piglets and seven Intermediate piglets (1.4-1.6 kg), and group C (n=31)-litters with 14 Intermediate piglets. Sows were weighed within 24 h after farrowing and on days 7, 15 and 19 of lactation. Feed intake was measured daily during lactation. Subsequent weaning-to-oestrus interval (WOI), farrowing rate and litter size were evaluated. Piglets were weighed at cross-fostering and on days 7, 15 and 19 of lactation. Average daily feed intake, body reserves at farrowing and weaning, and body reserve losses of sows during lactation were similar among groups (P>0.10). Litter weight differed among groups, at all moments of evaluation, with the higher weight being observed in C group (P<0.05). Daily gain of litter was similar among groups (P>0.10). Survival rates up to 7 and 19 days were similar among groups (P>0.10). The percentage of sows showing oestrus until Day 7 after weaning was lower (P=0.03) and WOI tended to be higher (P=0.08) in group C compared to group A. Farrowing rate and second litter size were similar among groups (P>0.10). Sows with WOI>7 days had similar number of weaned piglets, feed intake and body reserve losses (P>0.10) to those with WOI≤7 days. However, long WOI sows had heavier litters at weaning and higher lactation efficiency than short WOI sows (P<0.05). In conclusion, WOI can be compromised in sows suckling litters composed entirely of Intermediate piglets compared to litters composed of Light piglets. This effect seems to be mediated by a greater intensity of sucking by heavier piglets rather than by greater body reserves mobilisation.