Ruminal Volume Research Articles

Rumen Liquid Dilution Rate in Dairy Cows Fed Once Daily: Effects of Diet and Sodium Bicarbonate Supplementation1,2

Three ruminally cannulated Holstein cows fed total mixed diets of hay crop silage and concentrate (30:70, 50:50, 70:30, 100:0) were used to determine liquid volume ruminal and dilution rate with polyethylene glycol as a marker. Dosing 5h prefeeding produced nonlinear marker dilution curves that were divided into prefeeding, eating, and resting phases, whereas dosing 2h postfeeding produced linear dilution curves. Ruminal liquid volume calculated from either dosing method overestimated liquid volume compared to manual estimates. Mean liquid dilution rates did not differ between methods of dosing, and differences between diets were closely related to dry matter intake. Supplementation with 0, 68, or 114 g/day sodium bicarbonate did not affect ruminal liquid volume or dilution rates. Across diet and buffer treatments, liquid dilution rate during eating (23 to 32%/h) was greater than mean, prefeeding, or resting dilution rates (10 to 21%/h). Correct interpretation of ruminal volume and dilution data requires full details of dosing method, dosing time in relation to feeding, and sampling times.

Effect of Sodium Bicarbonate and Disodium Phosphate on Animal Performance, Ruminal Metabolism, Digestion, and Rate of Passage in Ruminating Calves

With a five-point radial response design, a control group, and several single factor points, effects of dietary sodium bicarbonate (0 to 4.5%) and disodium phosphate (0 to 2.0%) on calf growth, ruminal fermentation, ration digestibility, and rate of passage of liquid and particulate digesta were studied. Growth and intake data were collected age 7 to 14 wk. Rumen and blood were sampled three times. Digestion and rate of passage trials were during age 16 wk. Gains were not affected significantly but were maximized between 1 and 2% sodium bicarbonate and 0% disodium phosphate. Dry matter intake, feed efficiency, dry matter digestibility, volatile fatty acid ratio, ruminal pH, and buffering capacity were not altered by buffers. Ruminal osmolality and concentration of volatile fatty acids were increased by buffers. Digestibility of acid detergent fiber and neutral detergent fiber tended to be higher for rations containing buffers. Dilution rate of ruminal liquid increased by 40% with 2.0% sodium bicarbonate and .75% disodium phosphate, and ruminal volume was decreased. Passage rate of particulate digesta was increased by a similar amount.

Control of intrinsic reticulo-ruminal motility in the vagotomized sheep.

The intrinsic motility of the reticulo-rumen was studied by electromyography in nineteen sheep subjected to bilateral thoracic vagotomy and maintained by intragastric infusion of a complete liquid diet. The influences of distension, temperature and tactile and chemical stimuli on the intrinsic reticulo-ruminal motility were investigated. The level of electrical discharge in the reticulum and rumen in the first 3 days after vagotomy was increased progressively with distension without giving rise to the large group discharges characteristic of the long-term vagotomized sheep, and was reduced by atropine (0.1-1 mg kg-1) but not by hexamethonium (2 mg kg-1). In the long-term vagotomized animals, the frequency of the large group discharges over the reticulo-rumen varied with the degree of reticulo-ruminal distension. The discharges were absent below a threshold rumen volume; above the threshold they increased progressively with volume until a maximal rate of six to seven regular discharges per minute was established at large ruminal volumes. The discharges were abolished by atropine (0.1-1 mg kg-1) or hexamethonium (2 mg kg-1). With the rumen volume below the threshold, in all areas of the reticulo-rumen localized distension stimulated local discharge only and did not induce large group discharge. Replacement of rumen contents with an equal volume of 0.2 M-acetic, -propionic or -butyric acid buffered to pH 4.0 rapidly abolished the large group discharges over the entire reticulo-rumen. Replacement of rumen contents by an equal volume of 0.9% NaCl at 30 degrees C immediately abolished the large group discharges; at temperatures between 35 and 43 degrees C this had no effect. Gentle tactile stimulation increased local discharge in the reticulum and cranial dorsal sac but not in other areas of the rumen and did not affect large group discharge in any region. It is concluded that the intrinsic reticulo-ruminal motility of chronically vagotomized sheep is principally regulated by the degree of reticulo-ruminal distension. Like the C.N.S.-controlled motility of the vagus-intact sheep it is inhibited by high concentrations of volatile fatty acids. Local control mechanisms therefore may interact with central control in the over-all regulation of motility in vagus-intact sheep.

Intake, digestibility, ruminal characteristics and rate of passage of orchardgrass diets fed to sheep.

Four orchardgrass diets ranging in cell wall content from 60 to 78% were fed to sheep, and relationships among intake, digestion, passage and ruminal measurements were determined. As cell wall concentration increased, dry matter intake, digestible energy intake, dry matter digestibility and excretion rate decreased, while cell wall intake rumen volume, rumen cell wall and retention time increased. Indigestible cell wall intake was similar with each diet. It appeared that as digestible energy intake decreased, the sheep attempted to adapt by increasing ruminal ingesta volume, increasing ruminal ingesta cell wall and decreasing rate of passage; as cell wall concentration increased, indigestible cell wall limitation was manifested in decreased levels of feed and energy intake. Rate and extent of digestion appeared to be related to indigestible cell wall and appeared to be key factors in the control of cell wall turnover and feed intake.

Post-Prandial Ionic and Water Exchange in the Rumen

SUMMARY Following the feeding of 350g. of lucerne chaff, changes in ruminal osmolality and solutes were examined. After feeding, the concentration of most ruminal ions and the osmolality rose initially. The ruminal changes were followed by a rise in serum osmolality which was maintained for 8 hr. After the initial period, the concentration of all ruminal ions fell abruptly, this fall being associated with an increase in ruminal volume, a fall in ruminal osmolality and an additional rise in serum osmolality. These changes were ascribed to an inflow of water across the ruminal wall. Ruminal infusions of NaCl and glucose appear to confirm this conclusion. Measurements of ruminal volume and omasal flow rates showed a biphasic pattern and this pattern could be related to rumination. Total daily reticulo-omasal flow (t½ = 3½ hr.) was higher than expected from pen-fed sheep, and this was assumed to be due to the pattern of feeding. After making an estimate of salivary flow it was concluded that there is an inflow of water across the ruminal wall while the ruminal liquor is hyperosmolar and also while it is hyposmolar with respect to serum. The relationship of the post-prandial flow of water into the rumen from the extracellular fluid is discussed in relation to primary ruminal tympany.