LAUSR

The in vitro fermentation pattern of five sources of carbohydrates of differing nature (maize grain, MZ; sucrose, SU; wheat bran, WB; sugarbeet pulp, BP; and citrus pulp, CT) under conditions of high concentrate diets for ruminants was studied. A first 8 h incubation trial was performed under optimal pH using inoculum from ewes given a fibrous diet, to compare fermentative characteristics of substrates. As planned, incubation pH ranged within 6.3 to 6.6. The gas produced from CT was higher than MZ, SU and BP from 4 and 6 h onwards, and at 8 h, respectively ( p 0.05) on total volatile fatty acid (VFA) concentration, nor on acetate or propionate proportions, but butyrate was lowest ( p< 0.05) with CT and BP. The second incubation trial was performed in a poorly-buffered medium, with inoculum from ewes given a concentrate diet. All substrates showed a gradual drop of pH, being lowest with SU after 4 h ( p <0.05). Throughout the incubation, gas production was highest with CT and lowest with MZ and BP ( p <0.05). Total 8 h VFA concentration was higher with CT than BP, SU and MZ ( p <0.05). Acetate proportion was higher, and that of propionate lower, with BP than WB ( p <0.05), butyrate proportion being higher with MZ and WB than with BP and CT ( p <0.05). Lactic acid concentration was higher ( p <0.05) with SU than WB and BP. Fermentation characteristics and acidification potential of feeds depend on the nature of their carbohydrate fraction, and must be considered for practical applications.