Effect of full-fat rapeseed on digestibility and rumen fermentation in cattle

Abstract

The effect of whole crushed rapeseed on ration digestibility was determined with three bulls, average live weight 155 kg, and the effect on rumen fermentation with a heifer fitted with a rumen fistula. The basal diet (B) contained 50 % of grass silage and 50 % of rolled barley of total DM. In experimental diets 30 % of barley was replaced with crushed rapeseed fed either untreated (URS) or treated with 1.2% of Gasol solution (GRS). The feeding level was 80 g DM/kg W0.75 for the bulls and 60 g DM/kg W0.75 for the heifer. The average digestibilities of the diets were 73.9 (B), 71.6 (URS) and 72.7 % (GRS) for organic matter. There were no significant differences in apparent digestibility of crude protein or crude fibre. The digestibility of ether extract was higher (P < 0.05) and that of NFE lower (P < 0.01) on rapeseed diets. Nitrogen retentions were 28.4, 30.9 and 33.7 g/d, respectively, for the three treatments. On rapeseed diets the rumen pH was higher (P < 0.05) and the total VFA and ammonia N concentration lower (P < 0.01, P < 0.05) than on control diet. Rapeseed increased the proportion of propionic acid (P < 0.01) and decreased the proportion of butyric acid (P < 0.01) in rumen VFA. The rate of degradation of DM and CP in the rumen was slower for Gasol-treated rapeseed than for untreated rapeseed. Rapeseeds did not have a negative effect on the rate of degradation of silage or hay in the rumen determined by nylon bag method. But replacement of barley with rapeseed tended to decrease the degradation rate of silage crude protein. There were no significant differences between the treatments in blood constituents.