What is the purpose of fixing piglets to specific teats for nursing?

To make all the piglets in a litter grow evenly and stay strong, within 2 days after birth the piglets should be given manual assistance so that each piglet nurses from a fixed teat. The specific method is: after the sow has finished farrowing and is about to let down milk, let the piglets find teats on their own; after most of the piglets have found teats, make individual adjustments for the weak and the strong piglets, placing the weak piglets on the front teats, which have more milk, and the strong piglets on the rear teats, which have less milk. If there are few piglets and many teats, the strong piglets may be allowed to suckle from two teats with less milk. Generally, the teats are fixed in about three days.