Intestinal macromolecular transmission in underprivileged and unaffected newborn pigs: implication for survival of underprivileged pigs.

Passive immunisation of the newborn pig depends upon intestinal macromolecular transmission to the blood, which ceases within 18 to 36 hours after birth in fed pigs. Macromolecular transmission in newborn, unsuckled pigs was tested by gavage feeding bovine serum albumin and fluorescein isothiocyanate-labelled dextran (molecular weight 70 kDa) together with sow colostrum. Serum levels measured four hours after feeding showed that underweight pigs under 1.0 kg, both apparently normal and weak, had a greater capacity for transmission than did apparently normal pigs over 1.0 kg (unaffected). Weak pigs 1.0 kg, or more, had a transmission equivalent to that of unaffected pigs, indicating that they may be otherwise normal animals affected by birth. Splayleg pigs and their clinically unaffected littermates also showed a greater capacity for transmission than unaffected pigs; splayleg apparently involves the entire litter, although the expression of the syndrome varies. The capacity for transmission in the unaffected pig increased with litter size and decreased with an increase in weight and age after birth. In addition, it was shown that transmission was greater in pigs with higher glucose, insulin and alpha-fetoprotein concentrations and lower haemoglobin, cortisol and alpha 2-macroglobulin f concentrations at birth. It was concluded that immature pigs have a greater capacity for intestinal macromolecular transmission at birth than unaffected pigs over 1.0 kg. Since the capacity for macromolecular transmission decreases with age, the probability of their survival depends very much on the husbandry practices in the herd.