Published online by Cambridge University Press: 27 March 2009
In ruminant animals, it is well known that the physical form of feed considerably affects rumination behaviour, which is considered to be an importantfunction related to the utilization of roughage feed (Balch, 1971; Ørskov, Fraser & Gordon, 1974; Morgan & Campling, 1978). It is also clear that the act of chewing during rumination has an important role in the reduction of particle size of ingested food, and this might facilitate microbial degradation in the rumen (Umezu, 1966). Furthermore, it is also obvious that rumination behaviour is considerably influenced by changes of dietary chemical composition. Campling, Freer & Balch (1962) observed a marked reduction in time spent ruminating when urea was added to an oat-straw diet in cows, and they suggested that there are important interactions between the two factors (chewing and bacterial degradation) responsible for reducing particle size in the reticulo-rumen. Similarly, there are several investigations of rumination behaviour in relation to the digestion of roughage diet in sheep and cattle (Welch & Smith, 1969a; Thomas, Kelly & Wait, 1976; Sudweeks et al. 1975).