I .A technique for the separation and colorimetric estimation of z,4-diaminopimelic acid (DAP) using automated ion-exchange chromatography coupled with an acid ninhydrin detection system is described.2. Only traces of DAP were found in rumen protozoa and no DAP was detected in rumen fluid prepared by ultracentrifugation or dialysis.3. The concentration of DAP in rumen bacteria from sheep on a constant feeding regimen, and the ratio of nitrogen to DAP for these bacteria were found to be constant over a 3-month period.4. The method has proved suitable for the estimation of bacterial N in the duodenal digesta of ruminants.5. The contribution of bacterial N to the total N leaving the abomasum of a lactating cow fitted with a permanent re-entrant cannula in the duodenum was found to be 5 0 % .In ruminants a substantial proportion of dietary protein is fermented in the rumen, and the degradation products are utilized for microbial protein synthesis. The protein which becomes available for digestion and absorption beyond the rumen includes unchanged feed protein and microbial protein. ) and may be used to estimate the bacterial contribution to ruminal and duodenal nitrogenous constituents. This paper describes. an improved method for estimating DAP using ion-exchange chromatography and an acid ninhydrin reagent based on the procedure of el-Shazly & Hungate (1966). The method has been used to assess the daily contribution of bacterial N to the total N passing into the duodenum of a lactating dairy cow. K. HUTTON, F. J. BAILEY AND E. F. ANNISON M A T E R I A L S A N D M E T H O D S Experimental animalsA mature Clun Forest wether with a rumen fistula, given I kg hay and IOO g rolled oats once daily, was used as a source of rumen bacteria when samples were required to assess the variation in N : DAP ratio over a 3-month period for an animal on a constant feeding regimen.A 4-year-old lactating Ayrshire cow in the 8th month of lactation and yielding 8.3 kg of milk daily was used for the estimation of bacterial N entering the duodenum. This animal had a rumen fistula and a re-entrant cannula in the proximal duodenum about 7 cm from the pyloric sphincter. The maintenance requirement of the cow was supplied by barley straw and a protein balancer offered at 11.00 and 17.00 hours. Production concentrates (400 g/kg milk) were given at 7.00 and 16.00 hours. The total intake of nutrients was slightly in excess of the minimum requirements recommended by the Agricultural Research Council (1965). Paper impregnated with chromic oxide (72.2 g chromic oxide/zoo g paper) was added to the rumen of the cow once daily as a marker in the measurement of digesta flow. Collection and preparation of digestaRumen contents were strained through four layers of surgical gauze, and about 400 ml of strained liquor were centrifuged at IOO g for I min to remove protozoa and dense food particles, and to yield a bacteria-rich supernatant fluid. This bacterial fraction was centrifuged at 22 ooo g for 10 min to yield clarified rumen liquor (CRL) and a precipi...

Three healthy male subjects 20 years of age were exercised for 2—8 hr riding a bicycle ergometer or walking on a treadmill. Higher heart rates were found with the bicycle rides than with the walking exercises with equivalent oxygen uptakes. The subjects could not work on the bicycle ergometer at oxygen uptakes of 1.8 liters/min for more than 4 hr but could with this uptake walk 8 hr. The results indicated that an 8-hr period of exercise could be completed without undue fatigue whenever the energy cost did not exceed 35% of the maximum oxygen uptake where heart rates, oxygen uptakes, and rectal temperatures remained below 120 beats/min, 1.4 liters/min, and 38 C, respectively. The heart rate appeared to be the important factor for estimating 8-hr work endurance. A rate of 140 beats/min could not be maintained for more than 4 hr or a rate of 160 beats/min for more than 2 hr without extreme fatigue. Submitted on October 26, 1960

SummaryAn experiment was undertaken to examine the effects of the micronization process followed by grinding on the chemical composition of barley and on digestibility and nitrogen (N) retention in the growing pig. Micronization relative to normal grinding increased the dry matter (DM) content and starch availability in vitro and decreased the protein content of the cereal. Retention of N was not affected by the process but apparent digestibility of the DM, N and gross energy was improved. The improvement in digestible energy content of micronized barley over the ground grain was 3·8%. In a subsequent trial 24 pigs were individually and scale-fed a diet containing 75% of barley in ground or micronized and ground form over the liveweight range 33 to 80 kg. Processing treatment did not influence growth rate, DM food conversion ratio, killing-out percentage, deposition of backfat or area of ‘eye muscle’ in cross-section.

SUMMARYUsing phenylmercuric chloride (PMC) as the experimental fungicide it has been shown that spraying trees once in autumn at 0.05% and again just before bud‐burst at 0.01% reduced scab infection on blossom truss leaves by over 99% in the following spring. In another orchard 0.01% PMC sprays in autumn and just before bud‐burst, followed by fungicide sprays in spring and early summer, gave complete control of scab. In a third orchard, which was subject to contamination by ascospores from non‐treated apple trees, infection was reduced by 56.9% by one autumn and one pre‐bud‐burst spray of 0.01% PMC without subsequent anti‐scab sprays.

House, Sharnbrook, BedfidThe factors which control nitrogen metabolism in the ruminant can be separated into two groups. The first includes all factors other than the digestive tract which exert control over the metabolism of N within body tissues. This group includes hormone and protein interrelationships, hormonal regulation of tissue enzyme levels, and the role of the liver, kidney, heart, skeletal muscle and free amino acid pools in the regulation of protein metabolism. These aspects have been extensively reviewed recently (see Munro & Allison, 1964; Munro, 1970) and will not be referred to subsequently in this discussion. The second group is specific to the digestive tract and includes those factors which affect N metabolism within the tract and thereby control the end-products of N digestion. Since the aim of this review is to consider the regulation of N metabolism in the ruminant animal in relation to the manipulation of rumen fermentation, emphasis has been placed on the N metabolism in the rumen and on the ability of the products to meet the N requirements of ruminant tissues. N metabolism in the rumenThe supply of essential amino acids to extra ruminal tissues is dependent on the amount, composition and digestibility of dietary protein which escapes ruminal fermentation, and on the extent of microbial protein synthesis in the rumen. Since the availability of N for microbial cell synthesis is influenced by the recycling of ammonia-N and urea-N between the rumen and the tissues, recent quantitative studies on the dynamic aspects of the metabolism of urea and ammonia are also reviewed.