Differences between sheep and cattle in digestibility, voluntary intake and retention time in the rumen of three tropical grasses

Abstract

In the assessment of the nutritive value of feeds for animals, measurement of digestibility has been a basic index since 1860 (Schneider & Flatt, 1965). In this laboratory, measurements of digestibility and voluntary feed consumption using sheep have been the basis of feed evaluation procedures for over 20 years (e.g. Milford, 1960). The plants with which our group is concerned, however, are mainly grazed by cattle, and it is important to establish the degree to which extrapolation of results from sheep to cattle is justified for tropical pasture species. Many comparisons between sheep and cattle in terms of digestibility of dry matter and other aspects of feed utilization have been made using temperate pasture species hays, silages, grains and mixed rations; this area has been thoroughly reviewed by Schneider & Flatt (1965). Very few such studies have been made using tropical species, and most of those in Australia have involved the native species Heteropogon contortus (Siebert & Kennedy, 1972) or mixed H. contortus and Bothriochloa decipiens (Playne, 1978), providing material of low quality, containing less than 1% nitrogen. Playne (1970) used one introduced tropical species, buffel grass (Cenchrus ciliaris), and in that work only one of three harvests contained over 1% nitrogen. In the present work three introduced tropical species have been examined, covering a wider range of quality than has been reported previously.