Effect of defaunation and refaunation of the rumen on rumen fermentation and N-flow in the duodenum of sheep.

In order to confirm earlier fragmentary results, the effect of defaunation and refaunation of the rumen on the fermentation pattern and flow of N-components in the proximal duodenum of two sheep was investigated. Defaunation had no effect on acetic acid as a proportion of the total volatile fatty acids in the rumen, while the proportions of propionic acid increased with a concomitant decrease in butyrate. Refaunation resulted in lower acetic acid and higher butyric acid proportions. The concentration of ammonia N in the rumen was clearly decreased after defaunation, already indicating an effect of the elimination of protozoa on nitrogen metabolism in the rumen. Defaunation also increased significantly the flow of total N, non ammonia N and individual and total amino acids in the proximal duodenum. Defaunation resulted in higher bacterial growth efficiency, significantly in one sheep, but the decrease after refaunation was statistically significant for both sheep. Determination of rumen digestibility of organic matter and acid detergent fibre (ADF) revealed lower values in the absence of the protozoa, while total digestibility was only influenced to a much lower extent. This indicated a shift of digestion from rumen to the lower digestive tract. Finally, earlier work is discussed in the light of the present findings.

Stomach emptying of milk diets in pigs. A mathematical model allowing description and comparison of the emptying pattern.

The effect of doubling the nutrient intake in pigs fed a liquid cow's milk diet was investigated. This was done, either by doubling the volume given, or by doubling the dry matter content of the milk. There were two experiments in which the cumulative outflow of fresh contents, dry matter, crude protein and total carbohydrates, relative to the intake, was studied as affected by the treatments. This was done using pigs equipped with a simple duodenal cannula and an occluding balloon. The cumulative outflow curves indicated that the emptying process was biphasic both for the fresh contents and the nutrients emptied. A rapid emptying, followed by a period during which the emptying was inhibited was seen during the first emptying phase, the so called initial emptying. Thereafter the emptying was resumed again during the second phase: the final emptying. The individual emptying patterns were described very accurately by an adapted mathematical function with four parameters: y = c (1-2-(at)b)+dt3. The parameters c, b and a describe the initial emptying which is intrinsically exponential while d is descriptive for the final emptying. The appearance of the outflowing material, changing with time from unchanged milk, whey plus clot fragments, pure whey to whey with granular clot fragments indicated that the clotting of the milk was complete after about 15 min. The clotting certainly was responsible for the biphasic appearance of the emptying pattern. The emptying pattern of fresh contents was not related to the emptying pattern of dry matter and nutrients. Due to the rather high variability, there were no significant differences between the emptying patterns of dry matter and nutrients studied, although there were clear indications that crude protein was emptied at a slower rate than the other nutrients. Doubling the nutrient intake either by doubling the volume given, or by doubling the dry matter content of the milk did not change the initial emptying pattern to a great extent, except in the first experiment, where doubling the volume increased the relative amount of dry matter and nutrients emptied. A difference of gastric capacity related to a difference in age between the pigs used in the two experiments is thought to be the reason for this discrepancy. The relative amounts of dry matter and nutrients emptied during the final emptying phase on the other hand were inversily related to the amount of nutrients given.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of monensin on fermentation pattern and soybean protein degradation in the rumen of sheep.

The effect of a daily dose of 30 mg Monensin on rumen fermentation pattern and degradation of the crude protein fraction of soybean meal was investigated with sheep. Degradation parameters for soybean meal were measured by the nylon bag technique. Monensin increased propionic acid percentages in the rumen, with a concomitant decrease in acetic- and butyric acid proportions, thus confirming earlier work. Ammonia N concentration in the rumen was also lowered, indicating an inhibitory effect on rumen protein breakdown. However, no effect on degradation rate, degradability and effective degradability (only with one sheep) could be observed. Possible reasons for these findings are discussed. Amino acid analysis on the residues in incubated bags revealed slight changes in amino acid composition, but these changes were considered to be nutritionally unimportant.