Which species would NOT have a reticular groove?

• A. Horse
• B. Cow
• C. Pig
• D. Sheep

Answer: (A)

Milk routing through the esophageal (reticular) groove is an adaptation seen in newborn ruminants to send milk directly to the true stomach, bypassing the rumen, reticulum, and omasum. This lets the calf, lamb, or kid digest milk efficiently before their forestomach is fully developed. Horses, however, are non-ruminants with a simple stomach, so there is no need for or formation of this specialized groove. Because they lack a forestomach and the associated bypass pathway, horses do not have a reticular groove. Cattle and sheep are classic examples of animals with this mechanism in their early life, which is why they would have the groove, while the horse would not.