Crude protein and amino acid digestibility values in broilers for different soybean varieties and/or maturity groups

Abstract

Soybeans are the primary protein ingredient source in poultry diets fed as soybean meals (SBM). In a typical corn-soy-based poultry (broiler) diet, SBM contributes up to 70% of dietary crude protein (CP), which dictates the significance of quantity and quality of protein/amino acids (AA) in SBM in dietary formulation. The objective of these studies was to evaluate different varieties of soybean from different maturity groups based on amino acid and protein digestibility in vitro and in-vivo experiments. The soybean varieties that are considered in this study were from different MGs, including MG 3, MG 4, MG 4.5, and MG 5, which are mostly grown in the southeastern region of the United States. First, an in vitro study was conducted using a multi enzyme approach mimicking broiler gut digestion processes to evaluate the digestibility of soybean meal (full-fat and defatted SBM) from 12 different varieties. Second, an in-vivo study with four varieties representing four different maturity groups was selected. A total of 144 birds (Cobb 500) were randomly divided into 4 dietary treatments in cages (six replicate cages per treatment). Semi-purified treatment diets were formulated as follows: TRT1, diet formulated with MG 3 soybean meal; TRT2, diet formulated with MG 4 soybean meal; TRT3, diet formulated with MG 4.5 soybean meal; and TRT4, diet formulated with MG 5 soybean meal. For both experiments, one-way ANOVA and Tukey's multiple range test was conducted. The in-vitro results showed the highest digestibility values for amino acids for variety 7 of MG 4.5 group than other varieties (P < 0.05) for full-fat soybeans. The in vivo results showed that the feed conversion ratio (FCR) was lower in TRT3 and TRT4 groups compared to the TRT1 and TRT2 (P = 0.002). Both in-vitro and in-vivo findings implied that soybeans from MGs 4.5 and 5 could have favorable nutritional significance.

Keywords: Soybean varieties; amino acid digestibility; broilers; maturity group.