CHEWING ACTIVITY OF RUMINANTS AS A MEASURE OF PHYSICAL STRUCTURE - A REVIEW OF FACTORS AFFECTING IT

Sheep not only spend longer eating and ruminating kg-1 DM than cattle, but also react differently according to the quality of the feed. Variation in chewing activity within species is very high and mainly due to differences in ingestive capacity and body weight. Animals with a greater intake capacity seem to chew feed more efficiently, while heavier animals can cope with relatively more fibre, because the relationship of rumination capacity and body size is near unity. Heavily pregnant animals need more time to chew feed. Influence of physiological stage seems to depend on the nature and level of the ration fed. Transition from limited to full access time to feed or from restricted to ad libitum feeding is generally accompanied by a decrease of eating rate, which usually is partly compensated for by an increase in the rate of rumination. Protein content of the ration has a positive effect on chewing rate. With a decreasing forage percentage in the diet, chewing time kg-1 DM declines proportionally up to 50%, beyond this level, the rate slows down and can even reverse. © 1990.