Which animal species has an effective mechanical barrier that prevents vomiting?

Horses possess a highly effective mechanical barrier in the form of a strong lower esophageal sphincter, which is crucial in preventing the reflux of stomach contents into the esophagus and, consequently, vomiting. This anatomical feature is especially important for horses, as their digestive system is designed for a continuous grazing lifestyle, and the act of vomiting would be counterproductive to their gastrointestinal physiology.

In horses, the presence of this robust sphincter reflects their evolutionary adaptations to their herbivorous diet and the need to process fibrous materials efficiently. Unlike other species, such as dogs and cats, horses lack the ability to vomit, which is a significant aspect of their digestive health. Understanding this mechanical barrier's role is vital for recognizing the differences in gastrointestinal function across various animal species.