Ventricular septal defect (VSD) is a birth defect of the heart where there is a hole in the wall that separates the two chambers of the heart.
Calves with VSD may have difficulty breathing and seem short of breath and trouble drinking milk. Because of the heart defect, they will most likely be lethargic and be short of breath with any exertion. If the hole is small, the calf may only have a heart murmur and the defect would only be discovered with a post-mortem examination. Unfortunately, if the hole is larger the calf will most likely die at which point a vet can diagnose VSD if they perform a post-mortem.