Proceedings of the New Zealand Society of Animal Production.
1980, 40: 226
Proceedings of the New Zealand Society of Animal Production.
1980, 40: 226
(1) A range of feeds containing more than about 13% crude protein (CP could be divided into two categories: a high solution N group (fresh perennial ryegrass, white clover, a Lotus corniculatus variety (Empire) of low condensed tannin (CT) content and a casein containing feed), and a low soluble N group (dried forage hays, a fresh L. corniculatus variety (Maitland) of high CT content, barley-based feeds and formalin-treated casein containing feed). Within each group the daily NAN flow (% N intake) [Y] was linearly related to the apparent fractional outflow rate of rumen OM pool (FOR = duodenal OM flow rate - rumen OM pool size, d-1) [X]. The relationships for the high soluble N group, Y = 7.5 + 48.6X, and the low soluble N group, Y = 36.3 + 39.1X, showed similar values for the slope but different intercept values.
(2) That the lower NAN flow usually associated with the high protein solubility of fresh herbages can be overcome by the presence of CT in the feed. Thus, in sheep fed fresh L. corniculatus (Maitland) the higher level of CT (1.46 vs. 0.26% DM) resulted in decreased protein solubility and consequently a decreased rumen NH3 pool size; decreased protein degradation in the stomach; and an increase in the proportion of N consumed that was retained by the animal.
(3) Assessment of available low "available" N (i.e., less than about 13% CP or a major proportion of CP as HCHO-treated protein) exhibited greater NAN flows than would be predicted by the above relationship. This is interpreted as being due to influence of N recycling on these diets.
Keywords: NZSAPAB;
