OMASAL SAMPLING TECHNIQUE FOR ASSESSING FERMENTATIVE DIGESTION IN THEFORESTOMACH OF DAIRY-COWS

A procedure allowing digesta sampling from the omasum via a ruminal ca nnula without repeated entry into the omasum was developed. The sampli ng system consisted of a device inserted into the omasum via the rumin al cannula, a tube connecting the device to the ruminal cannula, and a single compressor/vacuum pump. Eight cows given ad libitum access to a total mixed diet were used in a crossover design to evaluate the eff ects of the sampling system on digestive activity, animal performance, and animal behavior. Results indicated that the omasal sampling syste m has minimal effect on normal digestive and productive functions of h igh-producing dairy cows. Dry matter intake was reduced (24.0 vs 21.8 kg/d; P < .02) and seemed related more to the sampling procedures than to the device in the omasum. Observations of animal behavior indicate d that cows with the sampling device were similar to control cows, alt hough rumination and total chewing times were reduced slightly. The co mposition of digesta samples was biased toward an over-abundance of th e liquid phase, but using a double-marker system to calculate digesta flow resulted in fairly small coefficients of variation for measuremen ts of ruminal digestion variables. This technique may prove useful for partitioning digestion between the fermentative portion of the forest omach and the lower gastrointestinal tract. The omasal sampling proced ure requires less surgical intervention than the traditional methods u sing abomasal or duodenal cannulas as sampling sites to study forestom ach digestion and avoids potentially confounding endogenous secretions of the abomasum.