In situ ruminal degradation and intestinal digestibility of dry matter and protein in expanded feedstuffs

Barley, oats, soybean meal (SBM), rapeseed meal (RSM), a cereal mixture containing barley, oats, SBM and RSM (40 : 40 : 10 : 10) and a protein mixture containing barley, oats, SBM and RSM (10 : 10 : 40 : 40), were expanded (Kahl-expander) at three treatment intensities; mild (130°C), medium (155°C), and high (170°C). Ruminal degradation of dry matter (DM) and protein, and intestinal digestibility of protein was measured with nylon bag methods (in situ). In addition, particle loss of protein associated with washing of the nylon bags, and aspects concerning the assessment of protein value of individual feedstuffs for feed mixtures, were studied. The expander treatment tended to reduce effective DM degradability (EDMD) in barley, oats, SBM and the cereal mixture, but not in RSM and the protein mixture. The expander treatment considerably reduced effective protein degradability (EPD) in barley, oats, SBM, the cereal mixture and to some extent in the protein mixture. In RSM, expander treatment reduced EPD only at high treatment intensity. The intestinal digestibility of protein was not reduced by the expander treatment in any of the feedstuffs. The expander treatment will therefore shift the site of protein digestion from the rumen to the small intestine. The particle loss of protein was high in barley and oats, but was reduced by the expander treatment, especially in oats. In SBM and RSM, expander treatment tended to increase the particle loss. Except for oats, correction for the particle loss did not reduce the effect of the expander treatment on EPD. In the mixtures, EPD predicted from individual feedstuffs was higher than measured EPD, but predicted reduction in EPD from individual feedstuffs by the expander treatment was in agreement with the measured values. Differences in EPD between expander-treated feed mixtures, and corresponding mixtures of feedstuffs expanded individually, were small. This result indicates that feed mixtures can be expanded as a whole and that there is no need for expanding each ingredient separately.