Abstract

Five successive trials were conducted using eight adult rams (Sudan desert sheep) to study the effect of restriction of water intake on some aspects of digestion and nitrogen metabolism. The feeds used in this study were berseem hay (Medicago sativa), lubia hay (Dolichos lablab), maize hay (Zea mais), a concentrate mixture, and dry desert grasses (hummra) (a mixture of Dactyloctenium aegyptium, Schoenefeldia gracilis, Eragrostis pilosa, Aristida funiculata and Aristida spp.).Restriction of water did not affect the digestibility coefficients of organic matter, crude protein and crude fibre significantly. The digestibility coefficient of ether extract was significantly reduced whereas that of nitrogen-free extract was slightly higher when water was restricted.The concentrations of ammonia and volatile fatty acids in the rumen and of urea in the blood were recorded before and 3 h after feeding. Increases in rumen ammonia and blood urea nitrogen concentration were reduced by water restriction except when hummra was fed.Restriction of water intake also slightly increased the in vitro rate of fermentation of rumen contents which is taken as a measure of microbial activity in the rumen, and the retention of nitrogen. These results are interpreted as indications of more efficient nitrogen utilization under conditions of water restriction.There were no significant effects of the treatments on changes in the concentration of volatile fatty acids.The significance of these findings in relation to the management of desert sheep in the arid parts of the Sudan is discussed with special reference to the effect of the level of dry-matter intake on nitrogen balance.

The digestion and retention times of milled hay diets were first studied in three sheep fitted with rumen and abomasal cannulae. The hay was milled through 5, 20 or 40 mm screens. Solubility of dry matter (D.M.) in water and rate of loss of D.M. from hay in nylon bags suspended in the rumen increased with fineness of grinding. Apparent digestibility of D.M. within the gut tended to fall with fineness of grinding, as did mean retention time (MRT) of a particulate marker, [ I03 Ru]phenanthroline ([ 103 Ru]phen), within the gut and of [ I03 Ru]phen and a liquid marker, [ 61 Cr]EDTA, within the rumen. Dry-sieved abomasal particles were much smaller than particles of any of the hay preparations, most passing through a 0-6 mm screen.A second experiment was made on four other sheep, fitted with rumen cannulae and given a similar hay, chopped to 50 mm or milled through 2, 5 or 20 mm screens. Apparent digestibility of D.M. within the gut fell significantly with fineness of grinding, from 55% with the chopped hay to 46 % with the 2 mm hay, as did MRT, from 45 to 40 h respectively. Rumen pH at 1 h after feeding decreased with fineness of grinding.In a third experiment, using the four sheep given chopped or 2 mm hay, retention times of particulate matter and of fluid in the reticulo-rumen and in the caecum-colon were measured. [ 103 Ru]phen and [ 51 Cr]EDTA were dosed together into either the rumen or the terminal ileum, and the rates of decline of marker concentration in rumen samples or faeces respectively were used to calculate the appropriate half times(

No abstract

The suitability of stained food and [ 103 Ru]phenanthroline-treated food as markers for measuring dietary retention time was examined in sheep. The digestibility of oat husk, assessed by incubation of samples contained in nylon bags in the rumen, was greatly depressed by staining with brilliant green, and slightly depressed by basic fuschsin. The latter effect appeared largely to be due to boiling rather than the stain itself.When milled hay treated with both basic fuschsin and [ 103 Ru]phenanthroline was introduced into the rumen, the mean retention time estimated with the stain was about 40% longer than that estimated with [ 103 Ru]phenanthroline.