Bovine Bloat and Choke Study Guide

Overview and Clinical Importance

Ruminal tympany (bloat) and esophageal obstruction (choke) are critical gastrointestinal emergencies in cattle that require rapid recognition and intervention. Bloat is an overdistension of the rumenoreticulum with fermentation gases, while choke refers to obstruction of the esophagus by foreign bodies or feed material. Both conditions can be rapidly fatal if untreated and represent significant causes of sudden death in beef and dairy operations. These topics are high-yield for the NAVLE due to their clinical prevalence and the need for immediate, decisive treatment.

Ruminal Tympany (Bloat)

Bloat is defined as overdistension of the rumenoreticulum with gases of fermentation. It is predominantly a disorder of cattle but can also occur in sheep and goats. The condition occurs when the normal eructation mechanism is impaired, leading to accumulation of carbon dioxide and methane in the rumen. Annual mortality rates from bloat can approach 1% in dairy cattle and up to 20% in severe pasture bloat outbreaks.

Classification of Bloat

Pathophysiology

Normal Eructation Mechanism

Under normal conditions, ruminants produce 30-50 liters of gas per hour through microbial fermentation. This gas (primarily CO2 and methane) rises to the dorsal gas cap in the rumen and is expelled through eructation (belching). The eructation reflex requires: (1) stimulation of tension receptors in the reticular wall by gas, (2) relaxation of the cardia, and (3) coordinated rumen contractions to move gas toward the cardia. Cattle normally eructate 15-20 times per hour.