Ruminal degradability and intestinal digestibility of protein and amino acids in barley and oats expander-treated at various intensities

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The objectives of the experiment were to study effects of pelleting or expander treatment at various intensities (mild, medium, hard or maximum) prior to pelleting at two temperatures in the mixer-conditioner (60 and 75°C) on ruminal degradation and intestinal digestibility of protein and amino acids in barley and oats, using nylon bag methods. Temperatures achieved were 85–95, 100–110 and 115–125°C at mild, medium and hard intensity, whereas maximum temperature achieved was 125°C for barley and 140°C for oats. Thus, temperatures higher than 130–135°C appeared unrealistic under commercial conditions. Pelleting decreased ruminal degradation of protein, especially at high temperature in the mixer-conditioner. Expander treatment decreased ruminal degradation of protein further and the lowest effective protein degradability (EPD) achieved was 30% for barley and 29% for oats, both obtained at maximum temperature in the expander and high temperature in the mixer-conditioner. These values are low compared to previous results and need to be verified. No negative effects of treatment on digestibility of protein were observed. This indicates that the treatments shifted site of protein digestion from the rumen to the small intestine. Expander treatment did not alter the contents of any individual amino acid either in barley or in oats. Expander treatment reduced ruminal degradation of total amino acids to the same extent as protein. The variation in ruminal degradation among amino acids was considerable. Thus, ruminal degradation of protein cannot be used for determination of ruminal degradation of all individual amino acids. Expander treatment did not increase the content of indigestible amino acids in barley or oats, indicating that amino acids were not heat-damaged.