INTERRELATIONSHIP BETWEEN HYPERSENSITIVITY TO SOYBEAN PROTEINS AND GROWTH-PERFORMANCE IN EARLY-WEANED PIGS

The objective of this growth trial was to determine the interrelationship between immunological criteria, gut morphology, and performance of starter pigs fed soybean proteins processed by different methods. One hundred twenty-five pigs were orally infused with 6 g/d of either dried skim milk, soybean meal (48% CP), soy protein concentrate, extruded soy protein concentrate, or experimental soy protein concentrate from 7 to 11 d of age and then fed a diet containing the same protein sources from weaning (d 21) to 35 d of age. All pigs were fed a corn-soybean meal diet containing 10% dried whey, 1.25% lysine, and 3% soybean oil for the remaining 21 d of the experiment. Xylose absorption and antisoy immunoglobulin G (IgG) titers were measured on d 6 postweaning, and skin-fold thickness after intradermal injection of protein extracts was measured on d 7 postweaning. A total of 25 pigs (five pigs/treatment) was euthanatized on d 7 postweaning. Villus height and crypt depth from duodenum samples were measured. These measurements were obtained to elucidate a relationship between the hypersensitivity responses to soybean products and growth performance of baby pigs. Pigs fed diets containing soybean meal had a lower (P < .05) rate of gain (d 0 to 14) and villus height, higher (P < .01) serum anti-soy IgG titers, and increased skin-fold thickness (d 6 and 7 postweaning) after intradermal injection compared with those fed dried skim milk. Pigs fed other soy proteins also had lower ADG from d 0 to 14 postweaning; however, pigs fed moist extruded soy protein concentrate tended (P < .09) to have higher ADG and improved feed utilization when compared with pigs fed soybean meal (d 0 to 14). Skin-fold thickness and anti-soy IgG titers (d 6 and 7 postweaning) were correlated negatively (P < .05 and P > 20, respectively) with ADG from d 0 to 14 postweaning. Results indicate that a model including skin-fold thickness and anti-soy IgG titers provided an estimate of nursery pig growth from d 0 to 14 (R2 = .33; P < .01). Villus height was related to ADG at d 0 to 14 postweaning (R2 = .40; P <.01) A combination of skin-fold thickness, anti-soy IgG titers, xylose absorption, villus height, and crypt depth provided the best estimate of growth from d 0 to 14 postweaning (R2 = .65; P < .05) in early-weaned pigs.