Effect of nutritional status, age at weaning and room temperature on growth and systemic immune response of weanling pigs

Two experiments were conducted to determine the effect of nutritional status, age at weaning and room temperature on growth and immune response of pigs. In the first experiment, 72 pigs were weaned at either 2 or 3 wk and fed either a complex, simple-adequate or simple-inadequate diet for a 24-d period. Total antibody (TAb) titers in response to injections of human red blood cells (RBC) on either 0, 4, or 16 d postweaning were not affected by age at weaning or dietary treatments even though the nutritional status was compromised to such an extent that pigs fed the simple-adequate diet gained at one-half the rate (.172 vs .349 kg/d) of pigs fed the complex or simple-adequate diets (P less than .01). In Exp. 2, the immunological response of 144 pigs weaned at 3 wk were evaluated at 4 and 8 d postweaning. Pigs were weaned into rooms that averaged either 25 or 18 C, and were fed either a complex or simplex-adequate diet at either ad libitum (AL) or restricted (Res) levels for a 24-d period. Restriction of either the complex or simple diet for the first 16 d of the trial drastically reduced (P less than .01) the growth rates of Res pigs compared with AL pigs (.042 vs .236 kg/d). There were no differences in skinfold thickness (Sf) or TAb, 2-mercaptoethanol sensitive (MEs) and resistant (MEr) antibody titers when pigs were inoculated with phytohemagglutinin-P (PHA-P) or RBC at 4 d postweaning regardless of room temperature, diet source or feeding level.(ABSTRACT TRUNCATED AT 250 WORDS)