Abstract

Sixteen high (HS) and 16 low (LS) bloat susceptible dairy cows were offered hay or pasture when not lactating and pasture or 75% pasture 25% hay when lactating. There were no significant differences between susceptibility groups in voluntary intake or apparent digestibility of DM, OM, nitrogen or energy on either occasion. There was a trend for HS cows to produce less milk of higher fat, protein and lactose content than LS cows. Rumen digesta studies on 5 HS and 5 LS rumen-fistulated, dry, pregnant cows at a maintenance level of feeding indicated that the proportion of digesta lost from the rumen after feeding was higher for LS cows than HS cows on pasture, but not on hay. There was no significant difference between susceptibilities in post-feeding fluid dilution rate. HS cows tended to have higher rumen fluid osmolality and Na concentration during the post-feeding period on pasture, but not on hay.

KL, Macmillan, HV Henderson, and AM Bryant

Proceedings of the New Zealand Society of Animal Production, Volume 44, , 71-74, 1984