Effect of volatile fatty acids, sodium and potassium bicarbonate in purified diets for ruminants

Intensive beef production 3. Performance of Friesian steers given low-fibre diets

Two groups of twelve-week-old Friesian steer calves were self-fed to a slaughter weight of 400 kg. on diets composed solely of either 85% rolled barley or ground maize and 15% of a supplement providing additionalprotein, calcium, phosphorus, iron, copper, cobalt, salt and vitamin A and vitamin D.

There were no health problems on the barley diet, but five of the 15 cattle given maize died from bloat.

Surviving animals on the maize diet took 344 days to reach a carcass weight of 231 kg.; comparable data for the barley-fed cattle were 362 days and 222 kg. The tenth rib cuts from the carcasses of cattle given maize contained significantly more fat and less water and ash than comparable cuts from the barley animals. Feed conversion ratio on the barley diet was 4·76.

A comparison between the Friesian steers in the present trials and others given a lower energy diet containing ground roughage showed that with increasing concentration of the ration there was an increase in rate of gain, killing-out percentage and content of ether extract in the tenth rib cut.

Another theory for the action of ruminal buffer salts: decreased starch fermentation and propionate production

Sodium carbonates have been fed to ruminants for more than 20 yr and, in many cases, have alleviated milk fat depression. These effects usually have been ascribed to increased ruminal buffering capacity, but this mode of action has several problems. For the buffering capacity to increase, the concentrations of ruminal bicarbonate, dissolved CO2, and Na have to increase. Ruminal fluid already is saturated with CO2, and the cation concentration of ruminal fluid is regulated closely to prevent hemoconcentration or hemodilution. Based on these latter observations, a significant increase in ruminal buffering capacity is unlikely. The action of bicarbonates is explained more easily by increased water intake, increased ruminal fluid dilution rate, increased flow of undegraded starch from the rumen, and decreased ruminal propionate production.

Growth and nutrient digestion by dairy heifers fed semipurified diets

Holstein heifers, which weighed an average of 154 kg, were randomly assigned to three dietary treatments in a split plot in time design. Differences in diets were fiber source: solka floc, corn cobs, and corn silage. The major source of added protein was corn gluten meal. Total collection metabolism periods were the final 7 d of each of two 30-d periods. Several heifers had simple digestive disturbances, which appeared to be related to low ruminal pH, while consuming the solka floc diet. Average daily gains were .78, .83, and 1.02 kg/d for treatments solka floc, corn cobs, and corn silage, respectively. Gains were within the range of acceptable growth standards and were higher than reports in the literature for semipurified and purified diets. Protein in corn gluten meal appeared to be utilized efficiently by the heifers for growth. The solka floc and corn cob diets are acceptable for growing dairy heifers where a low mineral content is desired but normal growth rates need to be maintained. The solka floc diet might be improved by including a buffer to help stabilize rumen pH.

Effect of a purified or corn-skim milk diet on retention and tissue distribution of manganese-54 in calves

Calves were fed a corn-skim milk or a purified diet to determine if the large differences in manganese metabolism in rats fed such diets also occurred in ruminating calves. The calf purified diet was similar to the rat purified diet but with potassium bicarbonate and sodium bicarbonate added as buffers to be suitable for ruminating calves. In contrast to the huge differences in rats, retention of manganese-54 was the same in calves fed the corn-skim milk diet as in calves fed the purified diet. It is unlikely that the minor differences in the diets caused such large differences in effects between calves and rats. A likely reason for the difference is the functional rumen in the calf. The active rumen may metabolize ingredient(s) that affect manganese absorption in the rat and, therefore, would not be in the small intestine to affect absorption by the calf.

The effect of potassium on the sodium requirements of growing steers with and without alpha-tocopherol supplementation

1. Hereford steers, housed in concreted yards and given demineralized water, were offered ad lib. a low-sodium (0.07 g Na and 4.5 g potassium/kg) basal diet of sorghum grain, urea and minerals, to which 0, 15 or 30 g K as KHCO3/KG diet had been added. Mean daily intakes of K were 26, 107 and 168 g/steer respectively. 2. The steers were given daily supplements of 0, 3.25 or 6.50 g Na as NAHCO3/steer, added to the food; mean daily intakes of Na (food plus supplemental NaHCO3 minus residues) were 0.41, 3.06 and 6.26 g/steer respectively. 3. Rate of gain of body-weight was positively related to the rate of Na supplementation and negatively related to the K content of the diet, but there was no interaction between Na and K contents of the diet. 4. the Na:K ratios for the parotid saliva from steers not given Na supplements was 0.3, whereas steers ingesting either 3.1 or 6.3 g Na/d had Na:K ratios of about 12. Increasing the amount of K in the diet had no consistent effect on the saliva Na:K ratio. The Na:K ratios for rumen fluid reflected changes in the saliva Na:K ratio in response to Na supplements and were inversely related to the amount of K in the diet. 5. The width of the adrenal zona glomerulosa from steers receiving the basal diet, without Na supplements, was significantly greater than that from steers given the Na supplements, but it was not affected by the amount of K in the diet. 6. Both Na supplements and the diet containing 30 g added K/kg significantly increased the Na:K ratio of the plasma. 7. The addition of 200 mg DL-alpha-tocopheryl acetate/steer per d to the diet had no significant effects on the growth rate of the steers. 8. It was concluded that the Na requirement of steers for growth was not signficantly affected by the amount of K in the diet up to 168 g/d.

Sulfate reduction by a Desulfovibrio species isolated from sheep rumen

Several dissimilatory, sulfate-reducing bacteria were isolated from the rumen fluid of sheep fed purified diets containing sulfate. One isolate, strain D, was selected for characterization. This organism is a nonsporeforming, obligately anaerobic, mesophilic, nonmotile, gram-negative, straight rod. Cell-free extracts show absorption maxima for cytochrome c(3) and desulfoviridin, characteristic of Desulfovibrio. Carbohydrates, as a sole carbon source, will support growth. Lactate supports growth in the presence of sulfate, not in its absence, whereas glucose or pyruvate support growth either in the presence or absence of sulfate. The isolate has a deoxyribonucleic acid base composition of 61.2% guanine plus cytosine, which is similar to that of several other species of Desulfovibrio; however, it differs from previously described species in morphology, motility, and carbon source utilization. Cell-free extracts of this bacterium exhibit adenosine 5'-triphosphate-sulfurylase, adenosine-5'-phosphosulfate-reductase, and hydrogenase activity. After incubation of cell-free extracts with adenine 5'-triphosphate and (35)SO(4) (2-), adenosine-5'-phosphosulfate rather than 3'-phosphoadenosine-5'-phosphosulfate was shown to be labeled, indicating that the pathway of sulfate reduction in this organism is similar to that of other dissimilatory sulfate reducers. This is the first report of a Desulfovibrio sp. isolated from the rumen.

Utilization of salts of volatile fatty acids by growing sheep. I. Acetate, propionate and butyrate as sources of energy for young growing lambs

1. An experiment was conducted in which sodium and calcium salts of acetic, propionic and butyric acids were given to groups of eight lambs as additions to basal diets of hay and concentrate. Two control groups were included, one group which received only the basal ration and one high-level control group which received sufficient additional concentrate to achieve growth rates greater than those of the groups receiving volatile fatty acid (VFA) salts. 2. With rumen-fistulated sheep, the effect on the rumen VFA composition and the pH of the rumen liquor, of diets supplemented with VFA salts given twice daily, was also investigated and compared with the effect of the basal diet alone. 3. The lambs receiving the VFA salts grew faster and achieved significantly greater empty body and carcass weights than those receiving only the basal rations; the high-level control group had significantly greater empty body and carcass weights than groups receiving salts of VFA. 4. There were no differences approaching significance in the efficiency of the three VFA in promoting gains in live weight, empty body weight and carcass weight. There appeared to be equal efficiency of utilization of the gross energy of the VFA and of the calculatedmetabolizable energy of the concentrates. 5. The effect of twice-daily feeding on the rumen VFA composition was that the concentration of the supple- mentary acid was greatest shortly after feeding, and about 5–6 h after feeding the effect was difficult to detect. There were no differences in the pH of the rumen liquor between animals given diets containing VFA salts and those given the basal ration.

THE ADDITION OF BUFFERS TO RUMINANT RATIONS: I. EFFECT ON WEIGHT GAINS, EFFICIENCY OF GAINS AND CONSUMPTION OF RATIONS WITH AND WITHOUT ROUGHAGE

A total of sixty-eight beef steers were used in three feeding trials to determine the effects of adding buffers to ruminant rations. The buffers used in these trials were sodium propionate and mixtures of sodium bicarbonate, potassium carbonate and calcium carbonate (as ground limestone). They were fed at levels varying from 2 to 9 pounds per 100 pounds of the concentrate ration. Data on feed consumption, weight gains and efficiency of feed conversion are presented.The addition of buffers to a ration containing timothy hay fed ad libitum did not prove beneficial. Buffers at the highest level (9 pounds per 100 pounds) were detrimental in the hay-concentrate ration. When the hay was removed from the ration there were highly significant decreases in weight gains and T.D.N. consumption. These decreases were partially offset by the addition of buffers to the all-concentrate rations. The results may have a practical application in the feeding of low-roughage rations.