EFFECTS OF EXPERIMENTALLY-IMPAIRED RETICULAR CONTRACTIONS ON DIGESTA PASSAGE IN SHEEP

The aim of the study was to evaluate the functional role of reticular contractions for digesta passage in sheep. Feed intake, mean retention time of fluid and plastic particles in the reticulo-rumen, rumen flui d volume, forestomach motility and particle size distribution in the f aeces were determined in five rumen-fistulated sheep fed on hay ad lib itum (Expt 1). The same variables were determined when reticular movem ents were impaired for 10 d by introducing a silicone-covered lead wei ght (500 g) into the reticulum (Expt 2). As feed intake dropped in Exp t 2 by 27 % compared with Expt 1, the sheep received in an additional experiment exactly the amount of feed which had been consumed during E xpt 2 and measurements were repeated without impairing reticular movem ents (Expt 3). The introduction of the weight did not affect the frequ ency of A- or B-cycles, but elevation of the reticular floor in a cran io-dorsal direction during the biphasic contraction was markedly reduc ed. The pattern of marker excretion indicated a drastically changed co mposition of reticular outflow in Expt 2 compared with Expts 1 and 3. During Expt 2, rumen fluid volume was similar to that in Expt 1 but ab out 25 % higher than that in Expt 3; the amount of large feed particle s in the faeces was increased compared with Expt 1 (+ 49 %) and Expt 3 (+ 76 %). In at least two sheep, abomasal emptying was inhibited duri ng Expt 2, as indicated by an enlarged impacted abomasum, In conclusio n, the results emphasize the central role of reticular motility for th e separation of particles in the forestomach, the outflow of digesta f rom the reticulo-rumen and transpyloric digesta flow.