Omasal sampling technique for assessing fermentative digestion in the forestomach of dairy cows.

A procedure allowing digesta sampling from the omasum via a ruminal cannula without repeated entry into the omasum was developed. The sampling system consisted of a device inserted into the omasum via the ruminal 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 effects of the sampling system on digestive activity, animal performance, and animal behavior. Results indicated that the omasal sampling system has minimal effect on normal digestive and productive functions of high-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 indicated that cows with the sampling device were similar to control cows, although rumination and total chewing times were reduced slightly. The composition of digesta samples was biased toward an over-abundance of the liquid phase, but using a double-marker system to calculate digesta flow resulted in fairly small coefficients of variation for measurements of ruminal digestion variables. This technique may prove useful for partitioning digestion between the fermentative portion of the forestomach and the lower gastrointestinal tract. The omasal sampling procedure requires less surgical intervention than the traditional methods using abomasal or duodenal cannulas as sampling sites to study forestomach digestion and avoids potentially confounding endogenous secretions of the abomasum.

Evaluation of some commercial media for the cultivation and enumeration of Clostridium perfringens from the chick intestine.

Four commercial media marketed for the detection and enumeration of Clostridium perfringens were found to adequately support the growth of a pure culture (ATCC 13124) of this species but enumeration of colony-forming units was difficult on Clostrisel and lecithin-lactose-agar base (LLA) media. Colonies of C. perfringens on LLA had typical opalescent zones, a distinctive feature that can aid in presumptive identification. Colonies on sulfite-polymyxin-sulfadiazone and tryptose-sulfite-neomycin (TSN) agar media were morphologically similar but black colonies were observed on TSN incubated at 46 C. Extreme difficulty was encountered in enumerating enteric bacteria from the chick intestine on Clostrisel medium because of the pinpoint size of the colonies and on LLA because of the opacity of the medium. Morphological characteristics of bacteria picked from colonies which formed after these media had been inoculated with chick intestinal contents were in sharp contrast to those of the pure culture of C. perfringens. Numbers of colony-forming units were higher than documented levels of C. perfringens in the intestine of chicks. These observations led to the conclusion that these formulations are inadequate for the selective cultivation and enumeration of this bacterial species from the intestine of healthy chicks, unless used in combination with further tests for specific identification.