Cross-fostering with up to two surplus piglets relative to sow functional teats: effects on performance and preweaning survival

In modern sows, litter size often exceeds the number of functional teats. Therefore, many farms retain surplus piglets within the litter. The present study evaluated the effect of cross-fostering biological litters with up to two surplus piglets relative to functional teats, allowing piglet replacement until day three of lactation. Females were selected (n = 201) at farrowing and evenly distributed among treatments: +0 (number of piglets equal to functional teats), + 1 (one surplus piglet), and + 2 (two surplus piglets). Biological litters were formed three to 12 h after farrowing (day 0). Piglets that died or were removed (low viability) during the first three days of life were weighed and replaced. Piglets in the + 2 group tended to have lower immunocrit values than those in the + 0 group (P = 0.06). Although the + 2 group exhibited the highest overall piglet loss rate across lactation (P ≤ 0.01), litter sizes in the + 1 and + 2 groups were larger than those in the + 0 group (P < 0.01). Piglets in the + 2 group also had reduced average daily gain compared with piglets in the + 0 and + 1 groups (P < 0.01). Facial and joint injuries were more frequent in the + 1 and + 2 groups on D5 (P < 0.01). No differences among treatments were found in udder injury scores, number of functional teats, sow body condition at weaning, daily milk production, or subsequent reproductive performance (P ≥ 0.10). Cross-fostering litters with up to two surplus piglets increased the number of piglets weaned without impairing sow performance, although individual piglet growth and early lesions were negatively affected.