The experiment included five studies to show the possible advantage of using soybean meal in a reduced-protein diet compared with substituting soybean meal with competitive protein feedstuffs (canola meal or corn-DDGS) in broiler chickens vaccinated or not for coccidiosis. The results show that partly replacing soybean meal with canola meal resulted in lower weight gain for the birds. Amino acid digestibility was consistently greater in birds that received soybean meal in their reduced-protein diets. Further analysis shows that part of the superior growth response seen in birds receiving the reduced-protein diet with soybean meal could be due to the enhanced immune response observed in the birds receiving that diet. Part-replacement of soybean meal with 10% corn-DDGS produced greater weight gain (though statistically similar to the diet with SBM). Therefore, it is possible that a specific feedstuff combination would enhance the benefit of using SBM in a reduced-protein diet.

This study showed promise in using soybean meal in diets with reduced protein. The reduction in crude protein is the future of the industry. The poultry industry has reduced the quantity of intact protein in poultry diets over the last few decades due to the availability of supplemental amino acids as well as the need to reduce the environmental effects of animal production. As other amino acids become available at competitive prices, the crude protein level in diets will need to be reduced to accommodate these amino acids because of the combination of environmental benefits, governmental regulations, or economic pressure. The current project (and the two that precede it) has built up evidence that using soybean meal in a reduced-protein diet is more advantageous than using the investigated competitive protein feedstuffs.