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Impact of level of soybean meal and β-mannanase in nursery diets on two genetic populations of pigs selected for soybean meal allergic response
A trial was conducted to evaluate 14 and 28% soybean meal (SBM) inclusion, with or without β-mannanase (Hemicell-HT® 1.5x, 0.08 MU/kg mannanase) enzyme on nursery pigs from two genetic lines selected for high (HL) and low (LL) sensitivity to soy proteins. Forty-eight pigs (initial BW = 6.35 kg (SD=0.86); 23 d age) were weaned into group pens with free access to a soy-free corn-milk product based diet. After a 4d adaptation, pigs were allocated in a randomized complete block design into individual pens, blocked by ancestry and BW, assigned to one of four treatments in a 2 x 2 x 2 factorial arrangement. Experimental diets consisted of: 28% SBM; 28% SBM + enzyme; 14% SBM; 14% SBM + enzyme. Feed intake and BW were recorded at d7 and d13. Data were analyzed using PROC MIXED in SAS. Interactions were removed from the model at P > 0.20. Feed efficiency was not normally distributed, so it was analyzed by logistic regression. For week 1, there were no differences between SBM levels for ADG, ADFI or G:F (P > 0.5). Pigs fed mannanase had greater (P < 0.01) ADG (181 vs 113 g/d) and G:F (0.585 vs 0.363). During week 2, pigs fed 28% SBM had greater (P < 0.02) ADFI than pigs fed 14% SBM, (500 vs 382 g/d) . During week 2 there was no difference for ADG (P > 0.05) for mannanase-fed pigs. The HL pigs had a 22% lower (P < 0.05) ADFI for the second week (0.463 vs 0.566 g/d). Overall there was no effect of SBM (P > 0.3) on ADG or G:F and 28% SBM tended to have greater ADFI (P = 0.07). Mannanase-fed pigs had a tendency for greater final BW (P < 0.06), ADG (P = 0.08), ADFI (P = 0.10) and G:F (P = 0.12) d 0-13. Overall, the LL pigs tended to have greater BW and ADG than the HL pigs (P = 0.09), however LL pigs had ADFI of 389 vs 326 g/d for HL (P = 0.05). Hemicell HT 1.5x had a positive effect on growth performance of weaned pigs fed soybean based diets, regardless of genetic sensitivity or level of SBM in the diet from day 4 to 17 post-weaning.
Keywords: Soybean; Allergy; Mannanase; Pigs; Genetic lines