EFFECT OF REPRODUCTIVE STATE AND CONCENTRATE SUPPLEMENTATION ON LIQUID AND PARTICULATE TURNOVER IN THE RUMEN OF EWES GIVEN AMMONIA-TREATED STRAW

Rates of passage of liquid and particulate markers (Co-EDTA, Or mordan ted fibres and Yb) were measured in ewes at late pregnancy lactation a nd non-breeding status. Animals were given ammonia treated barley stra w ad libitum supplemented daily with 250 and 550 (pregnancy), 550 and 850 (lactation) and 250, 550 and 850 (non-breeding) g of concentrate. The effect of the reproductive state was analysed only on ewes fed on 550 g of concentrate. Lactating ewes showed a higher voluntary straw i ntake (970 g/day) than pregnant or non-breeding ewes (720 and 790 g/da y respectively), but there were not significant differences in the OM digestibility (OMD) among reproductive states. Increasing concentrate supplementation promoted significant decreases in the voluntary intake of straw, associated with an enhanced OMD (P < 0.05). Fractional outf low rates (FOR/h) were higher in pregnant and non-breeding than in lac tating ewes, although differences were only significant (P < 0.01) for Chromium derived values. Ewes given 250 g of concentrate showed lower (P < 0.05) FOR than those given 550 and 850 g/day. Results support th e idea that in ruminants fed on low quality roughages, voluntary dry m atter intake is mainly restricted by rumen capacity, although the ener gy status of the animals might influence the extent of this restrictio n.