Microwave irradiation of whole soybeans in ruminant nutrition: Protein and carbohydrate metabolism in vitro and in situ

Whole soybeans serve as one of the main sources of protein in ruminant nutrition. Different processing methods have been employed for ruminal protein protection. The present study was conducted to determine the effects of microwave irradiation [900 W; 2, 4 and 6 min] on quality, ruminal degradability and estimated in vitro intestinal digestibility of availability soybean crude protein. This experiment was performed in a completely randomized design with seven treatments including control (no processing), along with 2, 4 and 6 min of microwave irradiation on whole and ground soybeans. Protein and carbohydrate fractions were determined according to Cornell Net Carbohydrate and Protein System (CNCPS). Triplicates of the samples were incubated in the rumen of three cannulated Holstein steers for up to 48 hr. Microwave irradiation increased neutral detergent insoluble nitrogen, metabolizable protein content and resulted in a lower effective rumen degradability and in vitro gas production. Nevertheless, longer processing time led to higher unavailable protein and carbohydrate fractions. In the main, microwave irradiation of ground samples for 4 min increased metabolizable protein content, without negative effects on protein and carbohydrate availability.