Bovine Abomasal Displacement (LDA and RDA): NAVLE Study Guide

Abomasal displacement is one of the highest-yield bovine GI topics on the NAVLE. The exam loves to give you a fresh dairy cow – high-producing Holstein, within 6 weeks of calving – with decreased milk, inappetence, and a ping. Your job is to know which side, what it means, and what to do about it.

Why It Happens

The abomasum sits on the right side of the abdominal floor in a normal cow. When motility drops, gas accumulates and the abomasum floats upward and migrates left (LDA, ~85% of cases) or stays right and balloons outward (RDA, ~15%). The key predisposing factor is decreased abomasal motility – and almost everything that stresses a fresh cow can cause it.

Risk factors cluster around the transition period. Negative energy balance from high-grain/low-fiber diets reduces rumen fill, giving the abomasum room to move. Concurrent diseases – metritis, mastitis, retained fetal membranes, and hypocalcemia – are the big four. Hypocalcemia directly impairs smooth muscle contractility throughout the GI tract. Retrospective studies show metritis or retained placenta co-occurs in roughly 38% of LDA cases. When the NAVLE gives you an LDA, always think: what else is wrong with this cow?