The use of an artificial rumen to assess low quality fibrous feeds

Abstract The results of two fermentation experiments conducted with an artificial rumen (rumen simulation technique—Rusitec) are reported. The first experiment compared the fermentation characteristics of a medium quality hay with those of untreated or urea—ammonia treated rice straw. Urea-ammonia treatment increased the digestibility, Volatile Fatty Acid production and microbial dry matter output compared with untreated straw. While the dry matter disappearance continued almost at the same rate up to 72h with urea supplemented straw, it levelled off after 48 h in the case o f ammoniated straw. The second experiement examined the effects of level of feeding and different roughage: concentrate ratios on fermentation characteristics of urea-ammonia treated rice straw. The output of VFA increased with the increase in feed intake and the level of concentrate in the diet. This was also accompanied by a steady decline in the acetate: propionate ratio. The ratio of VFA production: methane production was slightly lower for the high straw diets compared with in vivo values reported for good quality hay. However, increasing the quality of the overall diet by increasing the proportion of concentrate tended to increase this ratio to accepted values . It is clear that although Rusitec is an in vitro technique it has advantages over other in vitro techniques as it can provide much more information on rumen fermentation characteristics of a given feed. It is concluded that Rusitec is a valuable technique for evaluating fibrous residues and testing new diets before undertaking large-scale animal experiments.