Ruminal utilisation of pasture nitrogen in response to increased level
of dietary starch inclusion
E.S. Kolver, L.D. Muller and G.A. Varga
Dairying Research Corporation, Private Bag 3123, Hamilton
Proceedings of the New Zealand Society of Animal Production. 1998,
58: 106-109
Four diets based on high quality pasture were formulated using
additions of starch to contain 12.8, 19.6, 26.3, or 33% total
nonstructural carbohydrate and were evaluated using four continuous
culture fermenters during four 10 day periods. The true ruminal
digestibility of organic matter was not changed by diet but the
digestibility of neutral detergent fibre and crude protein linearly
decreased, and the digestibility of total nonstructural carbohydrate
linearly increased, as the level of starch inclusion increased.
Production of NH3 N was reduced linearly from 35.2 to 14.2 mg/dl
(P<0.001) and the flow of non-NH3 N as a proportion of total N flow
increased linearly from 66% to 83% (P<0.001) as inclusion of starch
increased. The quantity of microbial N and non-NH3 N flowing from
continuous culture was unchanged. The experiment indicated that if the
amount of organic matter digested is not appreciably increased by the
inclusion of nonstructural carbohydrate then the linear increase in
ruminal utilisation of pasture N arises more from a reduced pasture N
intake than an improvement in microbial protein synthesis.
Keywords: NZSAPAB;
Pasture; carbohydrate; microbial protein synthesis; nitrogen
utilisation; continuous culture.
Last Updated 12-09-1998
