Factors Affecting the Utilization of Food by Dairy Cows

Abstract

In any part of the digestive tract the time available for the breakdown and absorption of food is determined by the rate at which food residues pass through that piece of the gut. The reticule-rumen is a major site of digestion in the cow and the digestion of food, particularly the crude fibre fraction, is affected by changes in the rate of passage of the food through the reticulo-mmen, provided there are no compensating changes in the rate of breakdown of the food (Ralch, 1950; Balch & Johnson, 1950). Since undigested food can pass from the reticulo-rumen to other parts of the digestive tract only through the small reticulo-omasal orifice, the movements of this orifice are likely to influence the rate of passage of food.,The material passing through the reticulo-omasal orifice must come from the reticulum and possibly from the anterior part of the rumen. It will, therefore, tend to contain 90-95 yo water (Balch, 1950), particles of solid food and micro-organisms in suspension and substances in solution.Several observations suggest that there is a steady flow of digesta through the reticulo-omasal orifice throughout the day. Paloheimo (1939) slaughtered cows at intervals after giving them chromium sesquioxide, and found that the passage of this very heavy substance to the omasum had begun even in those cows killed immediately after administration. Phillipson (1946) suggested that there must be a constant flow of digesta through the reticulo-omasal orifice because the omasum, abomasum and intestines contain digesta at all times. In sheep the flow of digesta from the abomasum was found to be in gushes with usually less than 15 min. between each gush (Phillipson, 1948), which also suggests a continuous flow of digesta from the reticulorumen. The forces that activate the passage of digesta from the reticulo-rumen to the omasum are not fully understood. Wester (1926) and Schalk & Amadon (1928) considered that the movements of the omasum play an important part in drawing semiliquid digesta through the reticulo-omasal orifice into the omasum, but Phillipson (1946) did not support this contention. Both Wester and Schalk & Amadon described a sudden fall in pressure at the top of the pressure gradient in the omasum, illustrating the fall with kymograph records of varying clarity. Wester also gave a kymograph record of the contraction of the reticulo-omasal orifice.The present experiments were undertaken in order to study, in greater detail than was given by Wester or Schalk & Amadon, the relationship between pressure changes

Relationship Between Respiration and Movements of the Ruminant Stomach

“…Evidence that transfer of digesta from the reticulum most likely occurs during the second peaks of the biphasic reticular contractions is supported by work of Balch et al (1951). These authors skted that passage of digesta from the reticulo-rumen is largely controlled by a valvelike action of the omasum.…”

The mechanism of regurgitation during the process of rumination in the goat

“…These pressures measured by this technique show higher values than those previously recorded, e.g. 95 mm H20 (Quin, Van der Wath & Myburgh, 1938), 2-5 cm Hg (Wester, 1926) and 2-5-3-5 cm Hg (Balch, Kelly & Heim, 1951).…”

Effect of sward surface height on intake and grazing behaviour by lactating Holstein Friesian cows

“…Although there is some animal-to-animal variation, cows at pasture do not generally ruminate for periods longer than 50 min, mean duration being ≈30 min, and successive bouts of ruminating activity are interspersed with periods of jaw movement inactivity of similar duration (Figure 2). The regurgitation reflex during rumination is initiated by the presence within the reticulum and anterior rumen of fibrous material that stimulates the walls of those regions, in particular that surrounding the cardia (Balch, 1952). During the course of a rumination bout this material will become depleted, and the physical stimulus that it provides will be reduced.…”