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Effects of Heat Treatment on Soybeans With and Without the Gene Expression for the Kunitz Trypsin Inhibitor: Chick Growth Assays |
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L. L. Burnham, I. H. Kim, J. D. Hancock, A. J. Lewis |
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| Abstract |
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A total of 864 broiler chicks were used at Kansas State University and the University of Nebraska to determine the effects of heat treatment of two soybean genotypes on the growth performance. The soybeans were Williams 82 variety with (+K) and without (-K) gene expression for the Kunitz trypsin inhibitor. Heat treatment (autoclaving at 121째C and 1.1 kg/cm2) was applied for 0, 3, 6, 12, 18, and 24 min, resulting in a 2횞6 factorial arrangement of treatments. Station and station treatment effects occurred, indicating that response in nutritional value of the soybean genotypes to heat treatment varied from year to year and location to location. However, the interactions were in magnitude of response rather than direction of response, with greater reductions in trypsin inhibitor concentrations for the soybeans heat processed at the Nebraska location. Pooled data indicated that -K supported greater (p<0.001) ADG, ADFI and gain/feed than the +K genotype. As the length of heat treatment increased, the ADG, ADFI, and the gain/feed ratio increased for chicks fed both soybean genotypes (p<0.0001). However, heating the -K soybeans resulted in a greater response in ADG, ADFI, and gain/feed than heating the +K soybeans (genotype heat treatment interaction, p<0.001). Pancreatic weights (mg pancreas/g of BW) of chicks fed -K soybeans were reduced compared to those from chicks fed +K (p<0.001). Increasing heat treatment decreased pancreas weights in chicks fed both soybean genotypes (p<0.001). Chicks fed heated soybeans in the Nebraska experiment had lower pancreatic weights than chicks fed heated soybeans in the Kansas experiment (station heat treatment interaction, p<0.0001). Chick growth performance was improved and pancreatic weights decreased by feeding raw -K soybeans versus raw +K soybeans, and by increasing heat treatment of both soybean genotypes. However, the response to heat treatment was not independent of genotype. Both +K and -K soybeans heated for 24 min supported similar ADG, ADFI, gain/feed, and pancreas weights, although chicks fed raw +K soybeans had lower growth performance than chicks fed -K soybeans. In conclusion, raw -K soybeans supported greater growth performance in broiler chicks than raw +K soybeans, although this advantage was lost when both soybean genotypes were heated for 24 min. Heat treatment of +K soybeans supported similar growth performance to heated -K soybeans, even though +K soybeans supported lower rates and efficiencies of gain than -K soybeans when fed raw. |
| Keywords:
Soybeans; Trypsin Inhibitor; Heat Treatment; Chicks; Growth; Pancreas |
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