title: Weaning pigs at an early age decreases cellular immunity.
abstract: An experiment involving 118 pigs was conducted to evaluate the influence of weaning pigs at four different ages on in vivo and in vitro cell-mediated immunity. One-half of each litter was weaned at 2, 3, 4 or 5 wk of age; the other one-half remained with the sow as nonweaned controls. Phytohemagglutinin skin-test responses were determined on all pigs. Blastogenic responses of mitogen-stimulated lymphocyte cultures were determined before and after weaning. The intradermal response to phytohemagglutinin was reduced (P less than .001) in pigs weaned when 2 or 3 wk old and was suppressed (P less than .05) in those weaned when 4 wk old. In vivo cellular immunity was not altered by weaning in 5-wk-old pigs. The capability of lymphocytes to undergo blastogenesis in response to phytohemagglutinin was decreased in pigs weaned at 2 and 3 wk of age (P less than .001 and P less than .01, respectively). Pokeweed mitogen-stimulated blastogenesis was lower (P less than .01) in pigs weaned at 2 wk of age. Mitogen-stimulated lymphocyte blastogenesis was similar (P greater than .10) in control pigs and those weaned when 5 wk old. These data suggested that weaning pigs when younger than 5 wk old causes physiological changes detrimental to cellular immune reactivity. Those changes could alter disease susceptibility in young pigs.
mesh_terms: D000818:Animals; D007111:Immunity, Cellular; D007428:Intradermal Tests; D008213:Lymphocyte Activation; D013552:Swine / Q000276:immunology*; D014886:Weaning