Fermentation in the rumen of cows given rations containing hay and flaked maize or rolled barley in widely different proportions

Substrate and nitrogen metabolism of ruminant muscle was studied in vitro using a perfused sheep hemidiaphragm preparation. Glucose, acetate, propionate and butyrate were taken up by the perfused muscle at a constant rate over 2 h. Rate of acetoacetate uptake declined over the perfusion period. Net production of 3-hydroxybutyrate over the perfusion period was observed.Release of alanine and glycine by the perfused muscle could not be accounted for by protein breakdown, implicating muscle as a site of synthesis of these amino acids. The perfused muscle metabolized aspartate and arginine to a considerable extent, but the branched-chain amino acids only to a small extent. Only a small proportion, approximately 5 %, of the alanine produced by the perfused muscle was derived from glucose.In the presence of amino acids, at twice the concentration found in plasma, and insulin, some amino acids showed a net uptake by the diaphragm but when cysteine was omitted from the perfusate, all amino acids with the exception of arginine showed a net output. Evidence was obtained that protein synthesis was reduced in the absence of cysteine. The output of NT methylhistidine by the preparation was much higher than could be accounted for by estimates of protein breakdown using isotope dilution techniques. These data are, however, consistent with the view that NT methylhistidine is not a good index of muscle protein breakdown in sheep.

Section: Methodsmentioning

confidence: 99%

Metabbolism of perfused ruminant muscle

Coward

Buttery

1982

“…Volatile fatty acids in rumen fluid were determined by gas-liquid chromatography as described by Sutton & Johnson (1969).…”

Section: Methodsmentioning

confidence: 99%

The effect of protected lipids on nutrient intakes, blood and rumen metabolites and milk secretion in dairy cows during early lactation

Bines¹,

Brumby²,

Storry³

et al. 1978

Supplements of protected soya-bean-tallow were incorporated at 0, 1-7, 3-0 or 5-0 kg/day into a hay-concentrate diet and fed ad libitum to Friesian cows during the first 13 weeks of lactation.Intakes of supplement during weeks 1-6 were 0,1 • 34, 2-25 and 3-18 kg/day and during weeks 7-13, 0, 1-64, 3-10 and 4-24 kg/day on each of the respective treatments.As the lipid supplement increased there was a reduced intake of hay and concentrates, giving rise to reduced intakes of total, protein, and particularly 'carbohydrate' (non-protein, non-fatty-acid) energy. Apparent digestibilities, particularly of fibre, decreased as fatty-acid intake increased. After correcting for endogenous losses, true digestibilities of organic matter, carbohydrate, protein, non-fatty-acid lipid, total energy, calcium, magnesium and phosphorus were unaffected by the amount of supplement given, whereas fibre digestibility was reduced by increasing the supplement. Fatty acid digestibility was little affected up to an intake of 1-4 kg/day but above this there was a sharp reduction.Yields of milk, milk energy, protein, fat and lactose were increased at low lipid supplementation but reduced at the highest supplementation when amounts of protein and carbohydrate digested were lowest.Lipid supplementation reduced concentrations of rumen total volatile fatty acids in association with reduced, proportions of butyrate and. increased proportions of propionate. Plasma ^-hydroxybutyrate and magnesium were reduced and plasma free fatty acids increased in cows given lipid supplemented diets. There were no differences between treatments in plasma glucose, lactate or calcium nor in live-weight changes.

“…Samples were taken twice from each cow, at about 09.00 and 14.00 h, and were then stored at -20 °C. Subsequent analysis for molar proportions of volatile fatty acids (VFA) was by gas-liquid chromatography (Sutton & Johnson, 1969).…”

Section: Rumen Fermentation Studiesmentioning

confidence: 99%

Complete diets for dairy cows: a comparison between complete diets and separate ingredients

Phipps¹,

Bines²,

Fulford³

et al. 1984

One hundred and ninety-four lactating British Friesian cows were used over a 2-year period to determine the effects of mixing diet ingredients on dry-matter (D.M.) intake, animal performance, digestibility coefficients, rumen fermentation and efficiency of food utilization. Four treatments were imposed in both years and were complete diet and separate ingredients at ad libitum and restricted levels of feeding.In Expt 1 a complete diet at ad libitum and restricted levels of feeding was compared with separate ingredients. The diet consisted of 60 % concentrates and 40 % forage and contained 20, 20, 10 and 50 % on a D .M. basis of maize silage, lucerne silage, dried sugarbeet pulp and dairy compound, respectively. Method and level of feeding were the same in Expt 2; however, the diet in the 2nd year consisted of 50 % concentrates (40 % dairy compound, 10% dried sugar-beet pulp) and 50% grass silage.In Expt 1 cows fed the complete diet ad libitum consumed 16-5 kg D.M./day which was significantly more than the 14-3 kg/day consumed by those offered the separate ingredients ad libitum. Intakes in Expt 2 were not significantly affected by method of feeding. Much of the difference in Expt 1 was attributed to the fact that many cows rejected lucerne silage when fed in an unmixed form and therefore to keep the concentrate to forage ratio constant other diet ingredients were reduced proportionately.Mixing diet ingredients did not significantly affect milk yields, which were for the complete diet ad libitum and restricted and the separate ingredients ad libitum and restricted 22-2, 22-2; 22-1 and 20-7 kg/day in Expt 1 and 23-6, 20-8; 24-2 and 21-5 kg/ day in Expt 2, respectively. In Expt 1 when the concentrate to forage ratio was 60:40, cows fed the complete diet ad libitum produced milk with a significantly higher milk fat concentration (39-2 g/kg) than those fed the separate ingredients (31-6 g/kg). Similar effects were not recorded in Expt 2 when the concentrate to forage ratio had been reduced to 50:50. Changes in milk protein concentration were more closely related to changes in intake rather than method of feeding. Mixing diet ingredients tended to decrease live-weight loss in early lactation and accelerate live-weight gain in midlactation.In vivo digestibility coefficients determined in lactating dairy cows showed that in Expt 1 the D.M. and organic-matter digestibility coefficients for the complete diets fed ad libitum (0-689 and 0-713) were lower than those recorded (0-712 and 0-732) for the unmixed diet ad libitum. Although the digestibility coefficient of the acid-detergent fibre of the complete diet was markedly higher at 0-519 compared with 0-478 for the separate ingredients, the difference was not significant. In Expt 2 the only difference in digestibility coefficients was that for nitrogen, which for the complete diet was significantly higher than that of the separate ingredients at both levels of feeding.At an ad libitum level of feoding in Expt 1, the molar proportions of acetate and butyrate were 620 and 11...