Factors affecting diet selection by sheep. 3. Dry matter content and particle length of forage

Abstract

The effects of dry matter content and particle length of forage on potential intake rate and preference by sheep were investigated using six animals held in metabolism cages. In experiment 1, freshly harvested kikuyu grass (Pennisetum clandestinum) in its vegetative state was mixed in different proportions with similar material that had been oven-dried to form 15 diets ranging in dry matter content from 15 to 94%. Intake rate of wet matter decreased from 60 to 14 g/min as dry matter content increased, whereas the intake rate of dry matter increased from 9 to 14 g/min as the dry matter content of forage rose to about 40% but remained relatively constant thereafter. In experiment 2, undried kikuyu grass was eaten faster and formed a greater proportion of total intake than did dried kikuyu when expressed on a wet matter basis, but the amount of dry matter consumed from each forage was similar when they were offered together in separate containers. Kikuyu chopped to 10-mm length was eaten faster and was also preferred over kikuyu cut to 40 mm, irrespective of its dry matter content. Factors other than intake rate such as taste, odour or feel did not contribute markedly to the preference for either undried or dried kikuyu. Equations developed previously using results from dried forages predicted preference from intake rate quite well for dried forage but not for undried forage. It is suggested that the intake rate of dried forages may be a useful predictor of the preference for dry matter with forages containing any proportion of moisture, but further research is needed.