The effects of different temporal patterns of post-ruminal energy and protein supply on nitrogen metabolism in growing lambs
The ruminant is less efficient at utilising dietary nitrogen (N) for growth than the non-ruminant. Some of this inefficiency may be due to differences in the timing of energy and N absorption following a meal. In the non-ruminant, both energy and amino acids are absorbed together, relatively rapidly following a meal. By contrast, the ruminant absorbs its nutrients asynchronously and this may lead to reduced post-prandial anabolic stimulus. A series of experiments were conducted in which the effects of different temporal patterns of posts ruminal nutrient supply on whole body and tissue metabolism were assessed. When energy and protein were supplied twice daily in three hour pulses, thus mimicking the non-ruminant, urea production was markedly reduced whilst tissue insulin exposure over the twelve hour infusion cycle was increased. This combination most likely indicates that net amino acid retention was increased by the synchronous infusion pattern. Infusion pattern does not influence protein synthesis in muscle, skin, gut or liver, however, and therefore the changes in whole body urea metabolism are most likely mediated through modulation of proteolytic systems. Maximising the capture of N in the post-prandial period may therefore be a means of increasing the efficiency of ruminant production systems.