I . Four mature Friesian cows were used. For 2 weeks after calving they were fed 3 kg hay (147 g crude protein (nitrogenx 6.25; CP)/kg dry matter (DM)) plus g kg concentrates (177 g CP/kg DM) per d and thereafter 4 kg hay plus 12 kg concentrates/d.2. At approximately the 2nd, 4th and 9th weeks post-partum each cow was given a single intravenous dose of ["Clurea (I mCi) and [baH]glucose (1.5 mCi). Following this, jugular venous blood samples were withdrawn up to 26 h post-injection.3. The log (specific activity) Y. time curves were not linear for either metabolite. Glucose irreversible loss rates (IRL) were calculated by a stochastic procedure. The linear part of the urea log (specific activity) Y. time curve gave the same estimate for urea IRL rate as a stochastic method of calculation, but urea pool sizes were overestimated so that stochastic analysis of results was preferred.4. Mean milk yields at the time of the three measurements were 27.1, 30.8 and 27.9 kg milk/d. 5.Urea IRL was significantly lower (P < 0.05) in the first 4 weeks of lactation than in the gth, and blood urea concentration was lower (P < 005) in the 4th than in the 2nd and 9th week, but there was no close correlation between urea IRL and concentration.6. Glucose IRL rose (P < 005) between the 2nd and 9th weeks post-partum. perhaps due to the increase in feed intake. The results were generally consistent with the relationship between milk yield and glucose IRL established by Paterson & Linzell(1974).7. Urea IRL (y) and milk protein-N (x) production values were used to calculate the dficiency of protein utilization (EPU) as x+(x+o35 y). This assumes that 035 of urea IRL was due to protein catabolism.EPU was found to be 059-0.80 (mean 0.69).8. The possible contribution of catabolized amino acids to glucose IRL was calculated by assuming that 035 of urea IRL was due to protein catabolism and 0 2 of catabolized protein-(= passed through the glucose pool. On this basis the contribution of protein4 to glucosec was < 25 g/kg glucose IRL.Quantitative aspects of protein metabolism in dairy cows have come under close scrutiny with the publication, recently, of revised systems for defining protein requirements for ruminants (Roy et al. 1977). Application of these systems to dairy cows is limited by a general lack of reliable quantitative information on metabolic processes in cows. In particular there are no published values for direct measurements of the net transfer into milk protein of amino acids absorbed from the gut, although this is a critical factor in the new proposals. Oldham (1978) called this factor the efficiency of protein utilization (EPU) and suggested that it might be measured by quantifying the partition of amino acid-N supplied to the tissues between milk-protein N and amino acid-N oxidized to form urea. This paper presents the results of studies we have carried out using this technique.Because of the particularly high glucose demand of the high-yielding cow, and the need to synthesize a large proportion of this glucose via gluconeogeni...

1. Sheep fitted with rumen and re-entrant duodenal cannulas were given diets of approximately 200 g hay and 400 g concentrate mixture alone, or supplemented daily with 40 g linseed or coconut oils free or protected with formaldehyde-casein in a 5 x 5 Latin-square arrangement. Chromic oxide paper was given as a marker at feeding time and passage to the duodenum of neutral-detergent fibre (NDF) and different sugars were estimated from the values for c0nstituent:marker at the duodenum. Contributions of microbial carbohydrates to these flows were estimated from amounts of RNA present.2. The carbohydrate composition of mixed rumen bacteria from sheep rumen digesta were similar regardless of diet. Of the sugars entering the duodenum all the rhamnose and ribose and 0.51,0.24 and 0.35 of the mannose, galactose and starch-glucose respectively, were contributed by the microbes. Virtually all the arabinose, xylose and cellulose-glucose were contributed by the diet.3. For sheep receiving the basal ration, coefficients of digestibility between mouth and duodenum, corrected where necessary for microbial contribution, were 095,0.66,0.67,0.62,0.45 and 0.51 for starch-glucose, mannose, arabinose, galactose, xylose and cellulose-glucose respectively. Corresponding values when free-oil-supplemented diets were given were 0.95,035,0.38,0.55,0.01 and -0.02 respectively. Values for diets supplemented with linseed oil or coconut oil did not differ significantly. Addition of protected oils to the basal feed also resulted in depressed digestibilities of dietary structural sugars but to a far lesser extent than those observed with the free oils.4. Apparent digestibility of NDF was altered in the same direction as those of the main structural sugars, averaging 0.50,O. 17 and 0.29 in animals receiving the basal, free-oil-supplemented or protected-oil-supplemented diets respectively. The reasons for the difference between NDF and discrete carbohydrate analytical totals are discussed.

SummaryThree experiments were conducted to determine the effect of feeding polyunsaturated fish oils to dairy cows receiving rations of high, medium or low roughage content. In the rumen, the decreases in the proportion of acetic acid and increases in propionic acid induced by the oils became greater as the amount of oil given was increased but the magnitude of the response to any dose depended upon the composition of the basal diet. The effects on volatile fatty acids (VFA) proportions of small amounts of the oils (125–150 ml/day) were greatest with the low-roughage rations. With large doses of oil (375–450 ml/day) the responses were variable but it is concluded that, in general, changes in VFA proportions are least with low-roughage rations.The fat content of milk was more sensitive to dietary oil supplementation than were the rumen VFA proportions. When the unsaturated oils were given there was a decrease in milk fat percentage and an increase in the proportion of unsaturated fatty acids in the fat; there was also increased incorporation of fatty acids with more than 18 carbon atoms in the milk fat. The metabolism in the rumen tended to become adapted to the feeding of 150 ml/day of oil, the VFA pattern returning during the second and third week of supplementation to that observed before the addition of oil.

Goats are widespread throughout the world and provide hides, fibre, meat and m::k. In the UK, goats have been kept mainly in very small herds by hobby farmers, but commercial milk production has assumed increasing importance and has highlighted the need for sound nutritlonoi advice. Research is now providing an improved basis for feeding goats and results suggest that the nutrition of dairy goats is very similar to that of dairy cows.

Zusammenfassung Die Anlage von Intestinal‐Fisteln bei Milchkühen und ihr Einfluß auf die Milchleistung Es wird eine Technik zur Anlage von Umleitungskanülen am Duodenum oder von einfachen Duodenal‐ oder Ilealfisteln bei erwachsenen Friesians beschrieben. Die Operation der Tiere erfolgte während der Trächtigkeit. Die Futteraufnahme und die Milchleistung während der nachfolgenden Laktation zeigte keine wesentlichen Unterschiede zu nicht‐fistulierten Kühen bei gleicher Futterration.