PSX-36 Rumen protozoal dynamics of beef calves along transition from a milk/grass diet to a high-concentrate based diet: effect of tannins or medium-chain fatty acids as additives.

摘要

Changes in rumen protozoal community during adaptation of 5-month-old beef calves from a milk/grass diet to a high-energy diet based on (kg/kg) 0.74 cereal concentrate plus 0.13 wheat straw, both given (C), were studied. Eighteen rumen-cannulated Limousin crossbred male calves were randomly assigned to three experimental diets (C; C plus 0.02 quebracho and chestnut tannin extract, T; C plus 0.006 medium-chain fatty acid mixture, M). Ciliates were quantified and classified from rumen samples taken just before the morning feeding on days 0, 1, 7, 14, 21 and 30. No calves were defaunated at the end of the experiment, but three (one per diet) showed concentrations below 4 log cells/mL after 30 days. Besides, other four calves fed diet M showed absence of protozoa or concentrations below that level along the experimental period but were refaunated thereafter. On average, protozoal concentrations (log cells/mL) were 6.11, 6.35 and 3.81 after 7 days (