The effect of including Colombian rice polishings in the diet on rumen fermentation in vitro

The effect of including full-fat Colombian rice polishings, at 250 or 500 g/kg dry matter (DM) or defatted Colombian rice polishings (at 500 g/kg DM) on the fermentation of a basal diet of dried grass and medium-quality hay, in the rumen simulation technique (Rusitec), was investigated. With diets which contained 0, 0·25, 0·50 full-fat or 0·50 defatted, proportions of rice polishing, values for pH were depressed (7·22, 7·19, 7·11, 7·06 (s.e.d. 0·05)) and total volatile fatty acid concentrations were increased (52·8, 52·5, 75·5, 754 (s.e.d. 2·1) mmol/l) at the high levels of inclusion of rice polishings. Concentrations of ammonia (130, 140, 228, 209 (s.e, d. 64) mg/l) and total bacterial numbers (2·32, 2·70, 3·55, 442 (s.e.d. 0·82) × 10 8 per ml) were elevated by rice polishings inclusion. Numbers of cellulolytic bacteria (2·52, 1·74, 1·84, 2·10 (s.e.d. 0·60) × 10 6 per ml) and protozoa (19·8, 16·2, 15·8, 22·2 (s.e.d. 1·51) × 10 3 per ml were depressed (the latter significantly P < 0·01) by the inclusion offull-fat, but not by defatted, rice polishings.