Effects of pressure toasting on in situ degradability and intestinal protein and protein-free organic matter digestibility of rapeseed

BACKGROUND: Rapeseed is a protein supplement that contains up to 40% crude protein (CP) on a dry matter (DM) basis, but a large part of its protein can be easily degraded in the rumen. Therefore, before inclusion in ruminant's diet, the extent of its protein degradation in the rumen must be reduced without altering its intestinal digestibility. A study was conducted to investigate the effects of pressure toasting (T, 130 °C) at two residence times (1.5 and 10min) alone or in combination with soaking in water (ST, 4h) on ruminal degradability and intestinal digestibility of CP and protein-free organic matter (PFOM) in whole full-fat rapeseed. RESULTS: Regardless of the processing time (1.5 or lOmin), T significantly (P <0.05) increased the fraction of undegraded intake protein (UIP) compared to the untreated rapeseed samples. Soaking prior to further toasting did not improve the rumen degradation characteristics of rapeseed CP. Compared to the untreated rapeseed samples, both T and ST significantly (P <0.0001) improved the true protein digested in the small intestine (DVE) and degraded protein balance (OEB), effects that were more evident in samples heated for 10min. Soaking prior to pressure toasting, however, did not further improve the DVE or OEB in the rapeseed samples in comparison with T treatment. CONCLUSIONS: It was concluded that ruminal protein degradability of rapeseed decreased after pressure toasting, without seriously affecting its intestinal digestibility