Comparative study of intake and digestion of tropical and temperate forages

Abstract

Specific laws characteristic of intake and digestion of temperate forages have been generalised to tropical grasses. However, no study has confirmed if the laws established with temperate forages can be extrapolated and applied to tropical forages, because of the difficulty to compare these forages experimentally (climatic conditions, specific physiology). Consequently, we conducted a meta-analysis of a database by regrouping publications selected with some criteria (intake, digestibility, chewing time, rumen load…). The general results esta-blished between tropical and temperate forages were confirmed: crude protein, intake and digestibility were higher and cell wall and index chewing were lower with temperate forages than with tropical forages. Moreover, it appeared that at the same crude protein and NDF content, the hierarchies in intake and index of chewing were the same, whereas differences in digestibility disappeared. This result implies that when trying to valorise tropical forage, we have to focus on the improvement of intake and not on the improvement of digestibility. Our work seems to indicate the preponderance of physical mechanisms (chewing) relative to the biochemical mechanisms (cellulolytic capacities in the rumen) in the ingestive and digestive dynamics.