Effects of Synchronizing the Hourly Release of Energy and Nitrogen in the Rumen on the Metabolism and Performance of Growing and Lactating Sheep.

Abstract

The combinations of rate and extent of carbohydrate and nitrogen (N) release in the rumen on microbial protein synthesis and the production and metabolism of growing and lactating sheep was studied. In trial one the rate of release of organic matter (OM) and N in the rumen for 14 feed stuffs was characterised. The chemical composition and degradation characteristics varied between ingredients and also between batches of the same feed stuff. Using this data four diets were formulated and offered to growing lambs during experiments two, three and four. The diets were predicted to supply similar levels of metabolisable nutrients to the host, but differ in their predicted degree of synchrony of OM and N release in the rumen. Diets were offered at a restricted level during trials two and three to male lambs and ad libitum during trial four to ewe lambs. Rations were slow energy and synchronous, slow energy and asynchronous, fast energy and synchronous and fast energy and asynchronous. It was concluded from experiment two that there was no effect of hourly rumen synchrony on N retention however there were indications that there were differences in microbial growth and whole body energy metabolism. Trial three evaluated the rations for lamb growth rate, growth efficiency and carcass characteristics. It was concluded that diets supplying a synchronous release of energy and N to the rumen increased growth rates and growth efficiency of lambs, and that this may be due to differences in energy metabolism. It was concluded after experiment four that a synchronous release of energy and N in the rumen increased feed conversion efficiency of lambs, but not as a result of increased carcass weight. The aim of experiment five was to assess rumen synchrony on milk production and feed intake of Friesland ewes. Three diets were formulated to be synchronous, intermediate and asynchronous. It was concluded that rumen synchrony may offer a method to manipulate milk quality, and there were indications of differences in energy metabolism.