Effect of Roasting and Extruding on Nitrogen Fractions and Ruminal Degradability of Soybean Seed Protein

This experiment was conducted to determine nitrogen fractions and ruminal dry matter and protein degradability of raw or heated (roasted or extruded) soybean seed. Samples were incubated for 2, 4, 8, 16, 24 and 48 h in the rumen of 4 cannulated Kurdish male lambs (50 ± 3 kg BW). N itrogen fractions of samples were measured by chemical methods. Results showed that extruding decreased non-protein nitrogen (NPN) and acid detergent insoluble nitrogen (ADIN) in soybean seed. In compared with raw soybean seed, roasting decreased and increased buffer soluble nitrogen and neutral detergent insoluble nitrogen (NDIN), respectively. Lowest NPN and ADIN were observed in extruded soybean seed. Soybean seed extruding decreased and increased the rapidly degradable fraction (a) and the slowly degradable fraction (b) of protein, respectively. Roasting and extruding significantly decreased the rate of degradation (c). Effective degradability (ED) of soybean seed dry matter and crude protein significantly decreased by heat processing. Roasting and extruding had no effect on degradability potential of soybean seed dry matter and crude protein. The results of this experiment showed that heat processing significantly altered nitrogen fractions and decreased ruminal protein degradability of soybean seed. Also, extruding was better than roasting because it decreased NPN, ADIN, a fraction and ED and increased b fraction of soybean seed protein.