1. It has been shown that under a given feeding régime the concentration of blood urea in the sheep is constant.2. Changes in the diet lead to different levels of blood-urea concentration which can be correlated with different rumen-ammonia concentrations; the change in blood-urea concentration follows increases or decreases in rumen ammonia after a delay period of 4–8 hr.3. Fluctuations in blood-urea concentration in the sheep are not primarily due to changes in the overall nitrogen intake.4. It is suggested that these findings might form the basis of a supplementary test in assessing the value of the protein in a foodstuff for ruminants.

Three organisms, Clostridium kluyveri (Barker and Taha, 1942), Rhodospirillum rubrm (Kohlmiller and Gest, 1951) and an organism isolated from silage by Rosenberger (1952) and identified as Clotridium scatologenes, have been shown to synthesize fatty acids higher than n-butyrate, as end products of fermentative metabolism. In this paper we give an account of the isolation and properties of an anaerobic, gram negative organism which ferments certain carbohydrates and DL-lactic acid with the formation of hydrogen, carbon dioxide, acetate, propionate, n-butyrate, n-valerate, and n-hexanoate. The organism was isolated from the rumen contents of the sheep. MATERIALS AND METHODS Media. Except where otherwise stated the basal medium contained 0.4 per cent yeast extract (Difco), 0.05 per cent K1H2P04, 0.05 per cent NH4Cl, 0.03 per cent MgCl2.6H20, 0.03 per cent thioglycolic acid in tapwater; the pH was adjusted to 7.4. Medium A consisted of the basal medium plus 2 per cent soluble starch. Medium B consisted of basal medium plus 2 vol per cent of 70 per cent DL-sodium lactate. Rumen contents. The samples of rumen contents used were obtained from Scotch Blackface sheep fitted with rumen cannulae, and fed meadow hay and concentrates. Cultural techniques. Liquid enrichment cultures were carried out in 60-ml glass-stoppered bottles completely filled with medium. Agar plates were incubated in desiccators filled with H25 per cent C02 gas mixture and containing a capsule of

Digestibility studies were carried out to establish the inter-relationship between crude fibre and total lipid digestibility in the presence of added calcium or non-ionic detergents. Three levels of calcium, corresponding to daily intakes of 2-3, 4-8 and 22-9 g per sheep, were used in a predominantly ground barley diet (65 to 73 %) to which was added 8 % beef tallow or maize oil. Two non-ionic detergents were used at 0-1 % of the diet: nonyl phenol ethylene oxide and fatty alcohol combined with 3 molecules of ethylene oxide. With a daily intake of 2-3 or 4-8 g calcium per sheep, supplementation with fat resulted in a reduced fibre digestibility. When the intake was increased to 22-9 g, there was a significant improvement (P<005) only for the maize-oil-supplemented diet. Increasing calcium intake, associated with increased calcium digestibility, significantly (P<0-05) depressed total lipid digestibility. Intake of 4-8 g calcium per day was associated with the highest calcium digestibility of 33% digestibility units and the total lipid digestibility of 94%. Maize oil was better digested than beef tallow with the lower level of calcium; the position was reversed with the higher level of calcium supplementation. No advantages were found for crude fibre and total lipid digestibility when detergents were added. A possible mechanism by which the physical wetting of dietary lipids causes decreased digestibility of the fibre component is discussed.