A 12 week feeding trial utilizing four inclusion levels of a low alpha-galactoside soy protein concentrate was conducted with 224 Dekalb-XL chicken laying hens, seven hens per cage, eight cages per dietary treatment. Soy protein concentrate ranged from 0 to 18.65% of the diets. Soybean meal was used to make the diets iso-nitrogenous. Diets with the highest levels of soy protein concentrate resulted in significantly lower feed consumption and egg weights. No significant differences were observed in shell quality parameters.
A 6 week feeding trial was conducted with 240 Arbor Acre × Ross 1-day-old male broiler chicks, eight chicks per cage, six cages per dietary treatment. The four diets differed in the ratio of soybean meal and low alpha-galactoside soy protein concentrate used to provide protein, with soy protein concentrate ranging from 0 to 25.9% of the diets. The diets were formulated to be iso-nitrogenous and iso-energetic. Diets containing the highest amounts of soy protein concentrate resulted in significantly reduced feed consumption and weight gain. Feed conversion was not significantly affected.
Protein utilization studies were also conducted with 2- or 3-week-old male broiler chicks to compare the protein efficiency ratio of soybean meal, ethanol extracted soybean meal, and soy protein concentrates with five chicks per cage, six cages per protein source treatment. Chicks were given the test diets for a 2 week period. Feed consumption and body weights were recorded to compare protein efficiency ratios (PER) of the different protein sources. Ethanol extracted soybean meal resulted in greater protein utilization and amino acid availability than soybean meal. It was speculated that the soy protein concentrates required further heat treatment and methionine supplementation in order to obtain optimal protein utilization by chickens.