In ruminants, gastric juice is produced in the

In ruminants, gastric juice is produced in the abomasum. The abomasum is the fourth chamber of the stomach in ruminants, and it is functionally similar to the stomach of monogastric animals. It is also known as the "true stomach" because it is the site of protein digestion, which is not efficiently digested in the rumen or reticulum. The abomasum secretes hydrochloric acid and proteolytic enzymes such as pepsin, which break down proteins into smaller peptides and amino acids. The other options listed (omasum, reticulum, and rumen) are not primarily involved in the production of gastric juice. They are involved in the fermentation and absorption of nutrients from plant material, which is characteristic of the digestive system of ruminants.