In 34 lactating ewes (10 fistulated at the rumen and abomasum), herbage intakes were calculated using herbage digestibilities estimated either in vitro, or by using the plant cuticular wax component pentatriacontane (C35 alkane) as an internal marker. Alkane-based herbage intakes in intact ewes rose from 1672g OM/d at 14d of lactation to 2798g OM/d at 42d. In the fistulated ewes, the equivalent herbage intakes were 1736 and 2240g OM/d respectively. Alkane-based and in vitro-based intakes were not significantly different at 14d of lactation in either intact or fistulated ewes. Later in lactation, alkane-based intakes were significantly higher in both groups of ewes. In the fistulated ewes, estimates of the proportion of digested OM apparently disappearing across the rumen and of the efficiency of microbial protein synthesis were calculated from abomasal flows of digesta and microbial protein. These results suggested that the alkane- based herbage intakes were the more accurate.

TG, Harvey, R Haydon, HT Blair, D Daniell, and R Hilson

Proceedings of the New Zealand Society of Animal Production, Volume 50, , 423-426, 1990
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