Primary (Frothy) Bloat 

In frothy bloat, the normal gasses produced during fermentation become trapped in small bubbles within a stable foam, preventing eructation (belching). As gas pressure increases, the rumen expands, pressing against the diaphragm and lungs, which can suffocate the animal if not relieved. 

Causes and Risk Factors

• Lush, legume-dominant pastures: Especially alfalfa, ladino, red and white clover. 
• Succulent forages: Reduced saliva production and increased soluble proteins (like saponins and hemicellulose) promote foam formation. 
• High protein and rapid digestion: Fast-digesting forages release fine particles that trap gasses. 
• Feedlot diets: Finely ground grains and low roughage intake increase foam stability. 

Low risk legumes such as sainfoin, crown vetch, milk vetch, fenugreek, and birdsfoot trefoil contain tannins that bind proteins and reduce the risk of foam formation.

When it occurs

• Most common when cattle are first placed on lush legume pastures, particularly in the vegetative to early bud stages of growth. 
• Can also occur when feeding high-quality legume hay or during feedlot transitions. 

Symptoms

• Sudden, severe abdominal distension, especially on the left side. 
• Tight, rounded flank that may protrude above the backline. 
• Labored breathing, open-mouth breathing, or grunting. 
• Restlessness, frequent urination, or collapse if untreated. 

Treatment

• Frothy Bloat: Administer antifoaming agents (e.g. poloxalene, mineral oil, or dimethicone) orally or via a stomach tube. 
• Emergency Relief: In life-threatening cases, a rumenotomy (surgical incision into the rumen) may be necessary to release gas. 
• Prevention: Provide gradual adaptation to lush pastures, supply dry hay before turnout, and cons bloat-preventive supplements or blocks.