Which substance neutralizes the acidity of the stomach contents in the dog's intestine?

The substance that effectively neutralizes the acidity of stomach contents in the dog's intestine is bicarbonate. When food leaves the acidic environment of the stomach and enters the small intestine, it is crucial to neutralize the stomach acid to provide an optimal pH for intestinal enzymes and to prevent damage to the intestinal lining. Bicarbonate, which is secreted by the pancreas, plays a key role in this process. It helps to raise the pH of the chyme (the mixture of food and gastric juices) as it enters the small intestine.

While secretin is involved in the regulation of bicarbonate secretion from the pancreas in response to acidic chyme, it does not neutralize acidity itself. Instead, it stimulates the pancreas to release bicarbonate, which is the actual agent that performs the neutralization. Pepsin is an enzyme that works in the stomach and is inactive in the more alkaline conditions of the intestine, and chloride ions are involved in various physiological processes but do not play a direct role in neutralizing acidity. Thus, bicarbonate is the correct choice for its direct action in combating stomach acidity in the intestines.