Endoscopic observation of the reticulo-omasal orifice of cattle

Abstract

A variety of factors influence the voluntary intake of ruminants including reticulo-rumen fill or distension (Campling & Balch, 1961; Welch, 1967; Grovum, 1979) and rate of passage of digesta through the gastrointestinal tract (Bines & Davey, 1970). The exit point of the reticulo-rumen, the reticulo-omasal orifice, potentially serves as a control site in regulation of particle movement from the rumen.However, little definitive information on the functional behaviour of this anatomical location is available. Therefore, a fibre-optic endoscopic technique was designed to allow visual observation of the reticulo-omasal orifice in conscious, fed cattle.America, New Hyde Park, NY) and a 35 mm camera (Olympus 0M-2N with 1–9 focusing screen) was attached. Photographs were taken at a shutter speed of 1/30 or 1/60 sec. The film used was Kodak (ASA 160) tungsten balanced slide film. Prints were generated from slides using the Cibachrome P30 process. An Olympus CLK-3 cold light source, having a colour temperature of 3200 °K, provided the illumination for projection through the endoscope. Opening and closing of the reticuloomasal orifice were photographed using this procedure.

Faecal particle size distribution in captive wild ruminants: an approach to the browser/grazer dichotomy from the other end

“…The measurement of relatively larger openings in the RR in browsing ruminants (Hofmann 1973;Demment and Longhurst 1987) led to the conclusion that these animals do not retain ingesta in the RR as efficiently as GR (Hofmann 1989). However, it has been shown in cattle that the size of the ROO has no influence on the size of particles that escape -the ROO, when fully open, is much larger (five-to tenfold) than the critical particle size (McBride et al 1983). On the contrary, Nygren et al (2001) found that faecal particle size increased seasonally in the summer in free-ranging moose as the aperture size of the ROO decreased.…”

Factors Affecting the Mean Retention Time of Particles in the Forestomach of Ruminants and Camelids

“…The internal diameter of the ROO when fully open is five-to tenfold larger than the CPS (Bueno 1972-Bueno andRuckebusch 1974;Welch 1982;McBride et al 1983). This would suggest that the CPS may not be deter mined by the ROO and, further, that it might be possible for particles larger than the CPS to pass out of the RR.…”

Current understanding of the role of the reticulum and reticulo-omasal orifice in the control of digesta passage from the ruminoreticulum of sheep and cattle

“…These results indicate that reticular contractions have a role in discriminating between particles of the same length but with different densities and in preventing large particles from escaping from the RR. This suggestion is plausible when it is realized that the size of the opening of the ROO may not entirely be responsible for the small amount of large particles which ultimately escape from the RR (McBride et al 1983(McBride et al , 1984. In addition, and Dardillat and Baumont (1992) speculated that small dense particles may be trapped in the reticular cells.…”

“…However, a review of the literature shows that there is no unanimity regarding the relationships between the ROO and digesta flow (Mathison et al 1995). For example there is no agreement as to the exact timing of outflow through the ROO or when the orifice is open (Balch et al 1951;Stevens et al 1960;Ohga et al 1965;Ruckebusch 1970;Ehrlein 1980;McBride et al 1983;Dardillat 1987;Harmeyer and Michalowski 1991). In addition, although it is generally accepted that outflow from the RR occurs in association with the second of the diphasic reticular contractions (Baumont and Deswynsen 1991), we have recently reported that at least in solid-meal-fed compared with milkfed sheep the inactivity (relaxation of the ROO) may not be coincidental with reticular contractions Okine and Mathison 1996).…”