HIGH-PROTEIN AND LOW TRYPSIN-INHIBITOR VARIETIES OF FULL-FAT SOYBEANSIN BROILER CHICKEN STARTER DIETS

Two broiler growth trials of randomized block design were conducted to evaluate the nutritional quality of two new varieties of full-fat soy beans (SB) in starter diets. Use of the high protein (HP) SB (44% CP) has the potential to replace conventional soybeans in poultry rations and reduce the amount of SB needed. Use of the low-trypsin inhibitor ( LTI) SB may eliminate the cost of heat treatment before feeding to pou ltry. The protein sources were raw SB (39% CP, 70 Trypsin Inhibitor Un its (TIU) g-1 DM), autoclaved SB, autoclaved HP SB, LTI (42 TIU g-1 DM ) and commercially roasted SB. Diets were formulated to be isonitrogen ous and isoenergetic. Supplementation of diets with 0.3% DL-methionine was also studied, as the antiproteolytic activity of the TI makes sul phur amino acids less available for growth. Mean body weight gains, fe ed efficiency, dry matter and crude protein digestibilities and total carcass protein and energy content of the chickens fed HP, autoclaved or roasted SB were superior (P < 0.05) to those fed the raw SB diet. P erformance of the chickens fed the HP SB diet was similar to those on the roasted SB diet. Growth and feed conversion of chicks fed the LTI diet were similar to those fed the raw SB diet. However, mean pancreas weights of the chicks fed LTI were lower (P < 0.001) than those fed r aw SB which could be due to the lower trypsin inhibitor activity of th e LTI beans. Chickens given the methionine supplemented LTI diet made greater weight gains (P < 0.05) than those on the nonsupplemented diet . Heat treatment is required for the LTI beans. Full-fat HP soybeans m ay replace conventional soybean meal in broiler chicken starter diets if the formulation is adjusted for the differences in their protein an d fat contents.