As a result of placental structure and function, newborn pigs are born devoid of circulating immunoglobulins. A few days after birth, the maternally derived colostral antibodies are decreased in serum while immunoglobulin formation in these young piglets is still poorly developed or immature. Early weaned pigs may be particularly susceptible to disease during the early post weaning phase. At the time of weaning, changes in food and environment accompanied by transportation stress in segregated early weaning pigs enhances the possibilities of infection, hence, piglets may be immuno-compromised. In the segregated early weaning technique in multi site production units, pigs are transported a considerable distance from the farrowing unit to the nursery.
Weight gain is an important component in the economic efficiency of a commercial pig operation.
There is an association between disease and depressed weight gain. The body weight of artificially reared pigs is significantly less than that of sow reared piglets. Body weight at birth is an important component of cold resistance in the early postnatal period. A higher body weight is responsible for higher resistance to cold in the newborn pigs. The light weight at weaning makes pigs more susceptible to cold than pigs with higher weight and weaned at an older age.