VPB 121: Veterinary Physiology - II (2+1)

ABOMASAL MOTILITY

• Does not show cyclical rhythmic activity as that of the three compartments. Emptying of duodenum increases abomasal contractions.
• Enteric hormones (secretin, CCK, pancreozymin) produced by duodenal mucosa decreases abomasal activity and secretion.
• Distension of abomasum has negative effect on other three compartments i.e. distension of abomasum decreases the contractions of other compartments and delays the passage of food from omasum to abomasum.
• Duodenal receptors which are sensitive to composition of abomasal contents play a major role in abomasal emptying. Eg. osmolality of gastric chyme is the primary factor influencing abomasal emptying.
• Abomasum is always filled up each time as omasum contracts. Contraction of abomasum spreads through its walls forces the ingesta to move towards duodenum.
• Abomasum has two compartments pyloric antrum, body of the abomasum.  Pyloric antrum of abomasum is more active prior to feeding. Other than vagi, neuromuscular activity in the walls of the abomasum is of importance in maintaining abomasal motility.
• Abomasal motility is ceased when ruminant fed on high concentrate and low roughage diet, due to high VFA production.
• High concentration of butyrate, propionate limits abomasal motility other than the total volume of VFA produced.
• Contraction of abomasum expels abomasal gas back to reticulum.
• Grain feeding increases abomasal methane production. Methane poorly absorbed across the epithelium and is trapped in the abomasum and causes abomasal dysfunction like displacement.