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Impact of soybean meal level and β-mannanase in nursery diets on two genetic populations of pigs selected for soybean meal allergenic response
One-hundred ninety two pigs (initial BW = 6.67 ±0.05 kg; 23d of age) were utilized to evaluate the effect of 14 and 28% soybean meal (SBM) inclusion, with or without β-mannanase enzyme on nursery pigs from two genetic lines selected for high (HL) and low (LL) sensitivity to soy proteins. The 14 and 28% SBM diets contained varying amounts of milk products to make the diets similar in key nutrients. Pigs were weaned into group pens and fed a soy-free diet for a 6d adaptation period. Pigs were allocated in a randomized complete block design into mixed gender pens of 4 pigs/pen, blocked by ancestry and BW, assigned to one of four diets in a 2x2x2 factorial design for d0-19 followed by a common diet with or without enzyme for d19-33. Diets were: 28% SBM; 28% SBM + enzyme (0.08 MU/kg); 14% SBM; 14% SBM + enzyme (0.08 MU/kg) from d0-19 and 23% SBM with or without enzyme (0.08 MU/kg) from d19-33. For d0-19 there was a SBM by enzyme interaction (P=0.02) for ADG, 28% SBM enzyme improved ADG by 9.5% while 14% SBM ADG was reduced 6.8% by enzyme supplementation. Pigs fed 28% SBM had increased ADFI (P=0.002) but tended to have reduced G:F (P=0.07). The LL pigs had increased ADFI (P<0.03) but reduced G:F (P<0.01) compared with HL. For d19-33 and overall, there was a line by SBM by enzyme interaction (P=0.05) for ADG. The HL pigs fed 28% SBM plus enzyme supplementation significantly improved ADG (P<0.05) while in all other combinations of SBM level and line were not significant. For d19-33, pigs fed 14% SBM had improved G:F (P=0.01) compared with pigs fed 28% SBM. Overall, there was a SBM by enzyme interaction (P=0.05) for ADFI. Pigs fed 14% SBM, intake was reduced by enzyme addition while 28% SBM ADFI increased with enzyme supplementation. There was a line by enzyme interaction (P=0.007) for G:F, the HL had significantly improved G:F with enzyme supplementation (0.612 vs 0.658) whereas the LL had a slight numerical reduction in G:F (0.620 vs 0.600). Overall, HL pigs had improved G:F (P=0.04) and reduced ADFI (P=0.008) compared with LL. Pigs fed 14% SBM had improved G:F (P=0.01) compared with pigs fed 28% SBM. In high soy-sensitivity pigs fed higher SBM levels, supplemental β-mannanase has the potential to improve nursery performance (ADG and G:F) compared with the low soy-sensitive pigs.
Keywords: Soybean; Allergy; Mannanase; Pigs; Genetic lines