Acids In Rumen Research Articles

Volatile fatty acid production in the rumen of the grazing sheep: its use as an indicator of pasture value.

1. An isotope dilution method, known to be satisfactory for measurement of volatile fatty acid (VFA) production in the rumen under steady-state conditions, was tested for its applicability where the VFA pool in the rumen could vary irregularly. The method indicated mean production rates closely similar to those obtained when the pool size was virtually constant. Tests carried out in a model rumen confirmed this finding and the method was accepted as suitable for measurement of VFA production in grazing sheep.2. The method, modified to allow continuous sampling of rumen acids by dialysis, was applied to sheep grazing a mixed pasture. Mean rates of VFA production determined in seven sheep during fourteen 3-day periods throughout winter, spring and summer months ranged from 3.4 to 5.3 moles daily, production increasing during the period of growth of the pasture, and declining again with its drying-off.3. The pasture was at all times abundant; the findings are therefore considered to represent the pasture's full potential yield of VFA to the sheep and so to indicate its changing value in this respect as the seasons progressed.4. Results from sheep given roughages and from the grazing sheep indicated that, despite irregular intake, good predictions of mean VFA production rates could be made from mean VFA concentrations in the rumen fluid.

Ruminal acid production in lambs fed pelleted diets containing different levels of concentrates.

Two trials were conducted to determine the effects of pelleting and level of concentrates on rumen pH and volatile fatty acid production in lambs. Diets composed of all roughage or containing 20, 40, 60 and 80% concentrates were studied. Feeding of diets containing 40% or more concentrates consistently lowered the concentration of acids and pH in the rumen. Adding concentrates to the diets lowered the molar proportion of acetate and increased the proportion of propionate, butyrate and branched-chain acids. Pelleting the diet containing 60% concentrates decreased the level of acetate and increased the level of propionate. Higher levels of rumen acids were associated with pelleting the roughage portion of diets containing 20 or 80% concentrates. Pelleting the concentrate portion of a high-concentrate diet narrowed the acetate to propionate ratio to a greater extent than pelleting the complete diet. In vitro studies indicated that rumen microorganisms readily distinguished between levels of concentrate or soluble carbohydrate but could not detect differences due to the pelleting process. Pelleting did not influence the solubility of nitrogen in alfalfa hay or diet containing 20% concentrate. Pelleting tended to increase the solubility of nitrogen in high-concentrate feeds.

Some influences of rumen volatile fatty acids upon carcass composition and performance in growing and fattening steers.

Eighteen crossbred Hereford×Holstein steers were randomly assigned to treatment to investigate the influence of VFA levels on measurements of growth and carcass composition. Three pelleted diets with concentrate: roughage ratios of 0:10, 40:60 and 80:20 were the treatments chosen to produce variations in rumen acid levels. All rumen acids studied except butyric were significantly (P<.01) different due to diet. Means for calculated daily digestible energy intake did not differ significantly for the three diets fed ad libitum, yet carcass fat and protein tended (P<.10) to vary among treatments. The A/P ratio had a simple correlation of −.75 with carcass fat. When carcass weight was held constant, the A/P ratio had a partial correlation of −.73 with fat. Standard partial regression coefficients indicated that the A/P ratio was 5.5 times and approximately 2.5 times as important in regression on fat as carcass weight and daily gain, respectively. Combining carcass weight and daily gain in regression analysis was associated with only 6% of the variance in fat. Grade, dressing percent (P<.01) and carcass weight (P<.05) were negatively associated with the A/P ratio. A negative correlation (P<.01) was also found between the A/P ratio and daily gain.

The rates of production of volatile fatty acids in the rumen. III. Measurement of production in vivo by two isotope dilution procedures

(1) Production of volatile acid in the rumen of sheep fed at 12-hourly intervals on a mixture of wheaten hay and lucerne hay has been measured by two isotope dilution procedures involving continuous infusion of 14C-labelled fatty acid into the rumen and determination of the concentration of 14°C in the rumen acid throughout the feeding cycle. In the first procedure the varying rate of production was matched by a varying rate of infusion so that a constant concentration of label was maintained in the rumen acid. In the second procedure a constant rate of infusion was maintained and a mean value obtained for the concentration of label in the rumen acid during the cycle. Production values calculated from the data from both procedures were similar: approximately 5 moles of volatile acid were produced per kilogram of dry fodder. (2) This same rate of production was found for rations of 360, 450, and 675 g dry fodder fed at 12-hourly intervals.

The value of ethanol as a supplement to diet of straw, urea and molasses for sheep

The experiment was designed to see if any advantage was apparent that would justify the addition of ethanol to sheep diets containing oat straw supplemented with urea and molasses. Four sheep were offered an oat straw diet ad lib. with a molasses urea supplement. The treatment in the 4 x 4 Latin square design experiment consisted of the addition of 0, 4, 8, or 12 g of ethanol daily to the supplement. The following characteristics associated with each diet were measured : digestibility, rate of passage, rate of cellulose digestion in the rumen, food intake, nitrogen balance, and concentration of volatile fatty acids in the rumen. The only significant treatment effect was a faster rate of passage of food residues with the diet containing the highest level of ethanol compared with the diet containing no ethanol.

Interconversions and production of volatile fatty acids in the sheep rumen

1. Sheep fed at a constant rate were infused intraruminally with [1-(14)C]-acetate, -propionate or -butyrate during 5hr. periods. 2. Volatile fatty acids were estimated in the rumen contents and steady-state conditions were obtained. 3. Of the butyric acid carbon 60% was in equilibrium with 20% of the acetic acid carbon, and 2-3g.atoms of carbon were interconverted/day. 4. Little interconversion took place between propionic acid, acetic acid or butyric acid. 5. The net production rates for acetic acid, propionic acid and butyric acid were 3.7, 1.0 and 0.7moles/day respectively. 6. The production of volatile fatty acids accounted for 80% of the animal's energy expenditure.

Influence of Protozoa upon Rumen Acid Production and Liveweight Gains in Lambs

Influence of Protozoa upon Rumen Acid Production and Liveweight Gains in Lambs

Influence of Heat Stress on Rumen Acid Levels and Some Blood Constituents in Cattle

As part of a series of investigations to determine some of the internal body adjustments made by cattle in response to heat stress, studies were conducted in a psychrometric chamber to examine changes in rumen acids, blood glucose, ketones and hematocrit. Holstein cows and yearling Hereford heifers exposed to 90° F. temperature were compared with pair-mates kept under prevailing ambient conditions (36–78° F.). There was also a group of Angus heifers exposed to 100° F. for 7 weeks. Total VFA concentrations were lower at 90° F., with lower acetic acid concentrations being largely responsible. Changes in total VFA concentrations were consistently correlated to a significant degree with rectal temperature (−.49 to −.78**), and rate of respiratory evaporative loss (−.64 to −.71**), but the relationships of VFA levels to dry matter and water intake, blood glucose and blood ketones were quite variable. In the low temperature groups, rectal temperature was positively correlated with hematocrit, but in the chamber groups there was a negative relationship, dependent on the level of ambient temperature (−.22 to −.70**). Hematocrit was also negatively associated with respiration rate (−.59), respiratory vaporization (−.65**), surface evaporation (−.43) and dry matter intake (−.26) in the Holstein chamber group. Hematocrit had a positive but quite variable relation to rumen volatile fatty acid levels. Indications are that the direct effect of the heat stress will bring about some changes in rumen acid concentrations. The extent can not be discerned because of the indirect effects—viz., decreased feed intake and increased water intake taking place concurrently. Results from these studies indicate that changes in rumen acid levels and blood constituents (viz., hematocrit) may be involved in the adjustment to heat stress.

THE EFFECT OF EARLY WEANING ON THE BLOOD SUGAR AND RUMEN ACID LEVELS OF THE GROWING CALF.

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Ration Effects on Rumen Acids, Ketogenesis, and Milk Composition. I. Unrestricted Roughage Feeding1,2

Ration Effects on Rumen Acids, Ketogenesis, and Milk Composition. I. Unrestricted Roughage Feeding1,2

Metabolism of Amino Acids in the Bovine Rumen

Summary Catabolic intermediates of l-arginine, l-lysine, and dl-tryptophan in vivo were compared with previously determined dissimilation products of these amino acids in vitro. The relative concentrations of amino acids and amines of jugular vein-blood plasma were examined at 0, 1, 2, and 4 hr after administration of each amino acid, and rumen ingesta was assayed for amino acids, ammonia, indole, and skatole for a 24-hr period. dl-tryptophan (265.5g), l-arginine · HCl (274g), or l-lysine · HCl (237g) dissolved in one liter of water was mixed with the rumen ingesta of one of two rumen-fistula cows 2 hr after feeding 12lb hay and 8lb grain. Rumen ammonia concentrations were the largest 6 hr following arginine administration (32mg NH 3 -N/100ml), whereas tryptophan and lysine yielded smaller, but detectable, amounts of ammonia. Arginine yielded ornithine; the ruminal concentration of these two amino acids became equal within 6 hr after arginine administration. The ruminal lysine concentration decreased 50% within 6 hr of administration and this decrease was accompanied by an increase in delta-amino valeric acid concentration. Ruminal tryptophan concentrations were not markedly reduced until 8 to 10 hr after administration, at which time indole and skatole concentrations were 3 to 5 μ g/ml rumen fluid. Plasma indole and skatole did not exceed 0.25 μ g/ml through 4 hr. Arginine and lysine supplementation increased the concentration of several plasma amino acids within 1 hr after addition to the rumen, whereas tryptophan had little or no effect. Plasma lysine was markedly increased 4 hr after lysine administration.

Effects of Removing the Rumen, Reticulum, Omasum, and Proximal Third of the Abomasum on Digestion and Blood Changes in Calves

Summary Experiments were carried out with calves which had their forestomachs, upper one-third of abomasum with vagi, and spleen surgically removed. Some aspects of the nutrition, physiology of digestion, and levels of blood constituents were studied. Voluntary feed intake was found to be affected by stomach growth, anorexia, and scouring. Diets high in fiber stimulated the rumination cycle. Rate of passage of food was similar to that of simple-stomached animals. Results indicate that the decrease in blood sugar concentration which occurs in normal calves is independent of rumen development, dietary changes, or increased levels of volatile fatty acids in the functional rumen or in the blood. Changes in postprandial acetone body and volatile fatty acid levels were noted. The significance of these findings and the possible relationship between these factors are discussed.

The rates of production of volatile fatty acids in the rumen

The rates of production of acetic, propionic, and butyric acids in the normal rumen of a sheep have been measured from the decline in specific activity of these acids in the rumen after introduction of their sodium salts, labelled with 14C. Polyethylene glycol was introduced into the rumen to permit measurement of the rumen volume. The rates of production were: acetic acid 99 m-moles/hr, propionic 44 m-moles/hr, and butyric 21 m-moles/hr.

Studies on the Relationships between Rumen Acids and Fat Metabolism of Ruminants Fed on Restricted Roughage Diets

Summary The feeding of restricted roughage with high levels of concentrates produced significant declines in milk fat in lactating cows and goats. Associated with the decline in milk fat were a signficant increase in the concentration of rumen propionic acid and a decrease in blood ketone bodies. There was a decrease in arterial-blood acetic acid and in the arterial-mammary difference under conditions of ground and restricted-roughage feeding. The feeding of sodium acetate tended to increase low milk fat, and the feeding of sodium propionate tended to lower it further. An hypothesis regarding a mechanism of milk-fat depression based on the antiketogenic properties of propionic acid is discussed.

Development of Rumen Function in the Dairy Calf. II. Effect of Diet upon Characteristics of the Rumen Flora and Fauna of Young Calves1,2

Summary Twenty-four male calves were placed, at an average age of 3.5 days, on diets representing liberal and limited milk-feeding programs. The calves on limited milk were further divided into those receiving aureomycin in the concentrate mix and those not receiving it. In addition, a group of calves received only milk for 8 of the 12 wk. of the experiment. Rumen samples were taken weekly and analyzed for color, odor, consistency, total bacteria, aerobic bacteria, morphologically characteristic organisms, protozoa, the levels of niacin, biotin, and riboflavin, cellulose digestion, and the amounts of the lower fatty acids (C 2 –C 4 ). For calves fed solid feeds, the general pattern of rumen function development seemed to be a sharp fall in the aerobic bacteria within the first 3 wk., an increase in the total numbers of bacteria, and the establishment of protozoa. The rumen acids were at adult levels by 6 wk. of age; whereas, the protozoal and bacterial numbers approached this point a little later. The establishment of adult-type organisms and cellulose digestion were slowest to develop and were hindered by aureomycin and liberal milk feeding. Biotin, niacin, and riboflavin levels increased up to 7 wk. of age, with an indication of synthesis early in life.

Effect of Feeding Sodium Propionate on Milk and Fat Production, Roughage Consumption, Blood Sugar, and Blood Ketones of Dairy Cows

Summary A double-reversal experiment involving ten cows from the Cornell University Dairy Herd was used to detect the effect of the daily feeding of 1/2 lb. of sodium propionate on milk production, butterfat test, hay consumption, blood sugar and blood ketone levels. There were no significant differences (P In a supplemental experiment, two fistulated steers were fed propionate and control feed, and the fatty acid content of the rumen was determined at regular intervals after feeding. The feeding of the propionate feed resulted in higher levels of all the volatile fatty acids in the rumen for the first 3 hr. after feeding, particularly the propionic. From 3 to 9 hr. after feeding, the concentrations of rumen acids from the two feeds were quite similar. It was calculated that all of the administered propionate had disappeared in 7 hr., and most of it in 3 hr.

Some observations on volatile fatty acids in the sheep's rumen.

Some observations on volatile fatty acids in the sheep's rumen.

The Effect of Chlorobutanol on Certain Members of the B Complex in the Rumen and Blood Plasma Ascorbic Acid Levels

The Effect of Chlorobutanol on Certain Members of the B Complex in the Rumen and Blood Plasma Ascorbic Acid Levels

Rumen Synthesis of the Vitamin B Complex as Influenced by Ration Composition

Summary The addition of urea as a source of nitrogen definitely increased the synthesis of riboflavin, nicotinic acid, biotin and pantothenic acid in the bovine rumen when a readily available carbohydrate was present. Pyridoxine and “folic acid” could not be too closely correlated with ration composition. In the absence of a readily fermentable carbohydrate and probably a low population of microorganisms the synthesis of the members of the B complex is not at a maximum. The data indicate that thiamine may not be synthesized in the rumen. However, it seems more than probable that it is synthesized, but absorbed or destroyed at a rate greater than its synthesis.