Gastro-intestinal tract function in sheep infused with somatostatin

Area of Science:

• Animal Physiology
• Gastrointestinal Endocrinology
• Ruminant Nutrition

Background:

• Somatostatin is a key regulatory peptide in the gastrointestinal (GI) tract.
• Its precise effects on ruminant digestive physiology, particularly digesta transit and secretion, require further elucidation.
• Understanding somatostatin's role is crucial for optimizing ruminant nutrition and health.

Purpose of the Study:

• To investigate the physiological effects of continuous intravenous somatostatin infusion in anoestrous ewes.
• To determine the impact of somatostatin on digesta mean retention times (MRT) and GI tract segment weights.
• To assess somatostatin's influence on plasma hormone concentrations, abomasal secretion, and water balance.

Main Methods:

• Anoestrous ewes were infused intravenously with somatostatin (4.6 ng min-1 kg-1) for 5 days.
• Digesta MRT was measured using 51Cr-EDTA, 103Ru-phenanthroline, and lignin as markers.
• Plasma hormone levels, GI tract segment weights, digesta accumulation, abomasal secretion, and water consumption were analyzed.

Main Results:

• Somatostatin infusion increased plasma somatostatin, decreased prolactin and thyroxine, but did not affect insulin or glucagon.
• Post-ruminal GI tract weights decreased, with increased digesta accumulation in the abomasum and caecum.
• Total MRT was unchanged, but the proportion of time spent in the abomasum + small intestine + caecum increased, while large intestine and rumen transit decreased. Apparent endogenous abomasal secretion decreased, and water flow into the abomasum increased, alongside decreased voluntary water consumption.

Conclusions:

• Somatostatin directly influences the abomasal to caecal region of the ruminant GI tract.
• Observed effects in the large intestine and rumen may be secondary compensatory responses.
• The study suggests somatostatin's actions are direct and not mediated by other major GI hormones.