Search

The present study was planned to evaluate a role of nitric oxide (NO) in the regulation of regular ruminal contractions in conscious sheep. Intravenous infusion of S-nitroso-acetyl-DL-penicillamine (SNAP) at doses of 3-30 nmol kg(-1) min(-1)for 30 minutes inhibited both the amplitude and frequency of ruminal contractions in a dose-dependent manner. However, intravenous infusion of Nomega-nitro-L-arginine-methyl ester (L-NAME) at doses of 0.3-3.0 micromol kg(-1) min(-1)did not alter the basal tone of intraruminal pressure and the amplitude of ruminal contractions. The frequency of contractions was slightly inhibited by L-NAME infusion at 1.0 micromol kg(-1)min(-1). The effects of L-NAME were abolished by simultaneous infusion of L -arginine at 30 micromol kg(-1) min(-1). These results suggest that exogenous NO can diminish the ruminal contractions, while endogenous NO is not involved in the regulatory mechanism of basal tone and regular phasic contractions of the rumen in healthy sheep.

Six barrows of an average initial BW 27.5±1.2 kg were used. Each pig was fitted with two cannulas in different segments of the small intestine: pig 1 in the duodenum (C1) and upper jejunum (C2), pig 2 in C2 and the lower jejunum (C3), pig 3 in C2 and C3, pig 4 in C1 and the terminal ileum (C4), pig 5 in C3 and C4, pig 6 in C1 and C4. Pigs were also fitted with one catheter in the vena jugularis for blood sampling and with a second one in the arteria carotis for continuous infusion of 15N-leucine (4.2 mg/kg0.75 BW/d). Pigs were used in a crossover design experiment with three treatments and three periods of digesta collection (36 h) and blood sampling (36 h). Maize starch-based diets that contained: soyabean concentrate (SC), a mixture of toasted and untoasted soyabean meal (mSBM) of a high trypsin inhibitor activity, or rapeseed cake (RC) of a high NDF content were used in the experiment. The flow of endogenous and exogenous N along the small intestine and the net reabsorption rate of endogenous N were estimated. In the C1 digesta of pigs fed on the SC, mSBM and RC diets, total N was 138, 127 and 126% of the ingested N, respectively. Sixteen, 15 and 10% of the ingested N was absorbed up to C1, and 11.1, 11.6 and 9.4 g of endogenous N (Ed-N) per kg DM intake was secreted, respectively. For corresponding diets in the C2 digesta, total N was 126, 117 and 111% of the ingested N. Thirty four, 11 and 31% of the exogenous N (Ex-N) inflow and -32, 1 and -39% of the Ed-N inflow was absorbed. In the C3 digesta, total N was 44, 47 and 43% of the ingested N, while 81, 71 and 71% of the Ex-N inflow and 54, 38 and 49% of the Ed-N inflow was absorbed, respectively. Accordingly, in the C4 digesta total N was 24, 33 and 33% of the ingested N, and 45, 43 and 4% of the Ex-N inflow was absorbed. True N digestibility at the terminal ileum was 94, 88 and 82% for the SC, mSBM and RC diets. The reabsorption rate of endogenous N before the terminal ileum was estimated as 75, 51 and 69%, respectively. It was concluded that regardless of the dietary protein source, the middle segment of the small intestine is the site of the most intense absorption of endogenous and exogenous N. Reabsorption rather than secretion of endogenous nitrogen along the pig's small intestine seems to be influenced by dietary factors.

The stomach and small intestine manifest a myoelectric activity pattern called the migrating myoelectric complex (MMC), which is controlled by both environmental and intrinsic factors. The daily MMC pattern has been little investigated, therefore the purpose of the present study was to study it, in weaned pigs given food twice a day. A wireless telemetric recording system was used for 24-h electromyography of the antrum and duodenum. The activity of the antrum showed little change if any, whereas the myoelectric activity of the duodenum significantly changed with respect to the time of day and feeding in conscious pigs. Namely, there were more frequent and regular MMC cycles occurring in the duodenum at night as compared with that during daytime. This change was due to the shortening of phase II of the MMC cycles that were registered at night. Phase I of the MMC showed transient variability in relation to feeding with no impact on the day/night differences. Phase III of the duodenal MMC cycle as well as the ‘feeding pattern’ did not change along with the time of day and feeding regime. In conclusion, daily variation in the duodenum may provide different conditions for digestive processes in the day and night.