Even if there is a big difference in sizes between the pigs within a litter, they will be heavier at weaning if you do not move them to another sow. Use cross fostering to keep litter sizes even, one extra pig in the litter will reduce weaning weights by 0.4 kg per pig. Big pigs naturally do well. Use the management changes that require extra money, time, or labor to help the small birth weight pigs. Put them in smaller litters, on healthy, middle parity sows and provide them with supplements.
Small pigs benefit from split nursing.
When all of the pigs are born, take the largest pigs away from the sow for an hour, leaving the smallest pigs to suckle colostrum without competition. Keep the large pigs in a box, under a heat lamp so they will not get chilled. The age of the sow, the health of the sow, and the size of the litter all affected weaning weights. Compromised litters may benefit from additional supplementation. Pigs nursing sick sows are 0.4 kg smaller at weaning than pigs nursing healthy sows.