The use of field beans as a feed for broiler chickens

The chemical composition and physical characteristics of ten different UK grown field bean cultivar samples from the same harvest year were determined. Compositional variation existed between the beans. In the first experiment, diets that included each bean sample at 200 g/kg were used to compare broiler growth performance and determine available energy and nutrient utilisation. Relationships were examined between the nutritional variables measured in broilers and the laboratory characterisation of the field bean samples. Findings showed differences (P < 0.05) among the bean cultivar samples for feed efficiency, available energy and amino acid digestibility. A step-wise regression technique indicated that crude protein and ash content of the beans were the explanatory variables that significantly affected the previously unexplained variation in metabolisable energy and amino acid digestibility. The second study tested whether the addition of exogenous xylanase, phytase and protease, alone or in combination could improve the feeding value of beans for broilers. The enzymes had little or no effect on energy and nutrient availability for broilers. The third experiment looked at the use of a tannase-containing enzyme product (that additionally had α-amylase, xylanase, and pectinase activities) on the feeding value of a high tannin field bean cultivar. The enzyme increased (P < 0.05) dietary metabolisable energy, nutrient utilisation coefficients and also reduced the weight of the pancreas. The fourth experiment examined the impact of tannase-containing enzyme product on the feeding value of field beans with different tannin contents. The enzyme improved (P < 0.001) feed efficiency, energy, nutrient availability and reduced ileal digesta viscosity, despite tannin level in the beans. The fifth study demonstrated that micronising did not improve the nutritional value of beans for broilers. It was concluded that supplementation with the tested tannase containing enzyme mixture can improve the overall energy and nutrient availability of chicken diets, but not field beans specifically.