Effects of increasing trypsin inhibitor on nursery pig growth performance, fecal dry matter, and nutrient digestibility

Abstract

A total of 360 barrows (DNA 200 × 400; initially 6.1 ± 0.03 kg) were used in a 42-d growth trial to evaluate the effects of increasing trypsin inhibitor units (TIU) in complete feed on nursery pig growth performance, fecal dry matter (DM), and nutrient digestibility. At weaning, pigs were blocked by BW and randomly assigned to pens with five pigs per pen and 12 pens per treatment. There were six dietary treatments formulated to provide 1.4, 2.1, 2.8, 3.5, 4.2, and 4.9 TIU/mg of complete feed. Soy flour (76 TIU/mg) was added at the expense of soybean meal (5.4 TIU/mg) to create the experimental diets. Diet formulation was based on analyzed nutrient values of the soy flour and soybean meal, assuming digestibility coefficients for soy flour were equivalent to those of soybean meal. Experimental diets were fed in three phases: phase 1 from d 0 to 10, phase 2 from d 10 to 24, and phase 3 from d 24 to 42 after weaning. Feces were collected from three pigs per pen on d 10 and 42 to determine fecal DM, and d 42 fecal samples were used to determine apparent total tract digestibility (ATTD) of DM and crude protein (CP). Across all three individual phases and overall (d 0 to 42), increasing TIU decreased (linear, P < 0.001) average daily gain (ADG), average daily feed intake (ADFI), and gain:feed ratio (G:F). Fecal DM on d 10 increased (linear, P < 0.015; quadratic, P = 0.088) as TIU increased, with the majority of increase in fecal DM observed as trypsin inhibitor increased from 3.5 to 4.9 TIU/mg of complete feed. However, there were no differences in fecal DM on d 42. The ATTD of DM decreased then increased (quadratic, P = 0.003) as TIU increased with the lowest ATTD of DM observed at 4.2 TIU/mg of complete feed. The ATTD of CP decreased (linear, P < 0.001) as TIU/mg of complete feed increased. In conclusion, these data suggest that increasing dietary TIU above 1.4 TIU/mg of complete feed linearly decreased nursery pig growth performance and reduced the ATTD of DM and CP. Based on these results, each 1 TIU/mg increase in dietary TIU was associated with a 38 g/d, or a 7.4%, reduction in overall ADG. Overall ADFI decreased by approximately 40 g/d, or 5%, per 1 TIU/mg increase. Overall G:F decreased approximately 3% per 1 TIU/mg increase. Based on the amounts of SBM used in the diets for this study, and its TIU concentrations, soybean meal with greater than 5.4 TIU/mg has the potential to decrease nursery pig performance.