R.J. JONES and P. BARNES¹

Division of Tropical Crops and Pastures, CSIRO, Townsville, Queensland, Australia
¹Present address: Animal Research Institute, Achimota, Ghana, West Africa

Abstract

In vitro dry matter digestibility (IVD) studies using a modified Tilley and Terry (1963) technique were conducted using either strained cattle rumen fluid or the liquid from fresh cattle faeces as sources of inoculum. The dried leaves of 14 tropical leguminous shrubs in the genera: Acacia, Calliandra, Gliricidia, Leucaena and Zapoteca were used as substrates together with 3 standard forages of known in vivo digestibility.
The IVD values from using faecal fluid were linearly correlated with those obtained with rumen fluid (r = 0.982; P < 0.001).
The faecal fluid gave significantly (P < 0.001) lower digestibility values than those obtained with rumen fluid (by 3.5 percentage units).
Shrubs differed greatly (P < 0.001) in IVD with a range of 22–80%. There was no significant interaction in IVD (P > 0.05) between legume substrate and inoculum source.
On the basis of these results, it was concluded that the liquid fraction of cattle faeces provides the same precision as rumen fluid for in vitro digestion studies to rank tropical leguminous shrubs on the basis of their digestibility. In many situations, it may be easier to use faeces rather than to collect rumen fluid as an inoculum source for IVD studies, especially in developing countries.