Every now and then we see a clinical case so “textbook” that we simply have to snap a photo, and this was exactly the case this month for me. Listerial meningitis (or just Listeriosis) is a neurological condition caused by the bacterium Listeria monocytogenes that lives in soil and some plant matter. The above-optimal pH of spoiled or mouldy silage (pH >5) allows for these bacteria to survive and flourish due to incomplete fermentation.

Following ingestion, the bacteria can sometimes gain entry to an important nerve controlling the muscles on one side of an animal’s face, through small abrasions in the mouth (or shed teeth as is often the case in yearlings) before following the nerve up into the brain. Here it is well protected from the immune system and any systemic antibiotics we may administer, requiring prolonged courses of very high dose antibiotics. If any of the symptoms below sound familiar, call your vet to discuss the best treatment option as soon as possible.

This Devon cow pictured had been one of a group of pregnant sucklers due to calve this spring. Due to tight feed stocks (no surprise after this drought summer), the owner was forced to source some emergency silage bales which turned out to have been cut and baled somewhat roughly – to the extent that the owner reported finding visible clumps of soil inside the bales, though he had thought they were eating around them. As you may be able to make out, her right eyelid was ever so slightly drooping relative to the left, and she is clearly drooling from the right side of her mouth. Aside from missing the “classic” droopy ear, we have the early calling cards of Listeria – due to the damage done to a nerve on one side of the face, creating this “stroke-like” facial asymmetry.

When I arrived, she was leaning insistently against this fence post for balance and would not be moved, even as I injected her. Cattle with this condition have a strange “propulsive tendency” and are often found wedged into corners, cubicles, or fences – often pressing their head into walls. As the condition worsens they can also end up circling incessantly. What is not obvious from the photo is the slightly hunched back, leading the owner to wonder if she had bellyache. She may well have done, as they struggle to swallow properly due to the nerve damage, resulting in drooling and saliva loss. The rumen content dries out as a result, leading to rumen impaction and abdominal pain – this can manifest also as teeth grinding and grunting.

It’s beyond this article to fully lecture you all on proper silaging technique but good fermentation is aided through cutting grass at an early growth stage containing high fermentable sugar content, wilting for 24 hours and the use of organic acid or sugar-based silage additives. Ensuring a tight seal on all bales/clamps and care while moving and stacking bales to ensure the integrity of the wrap seal is paramount to preventing aerobic bacterial multiplication within the bale and spoilage. Reduce soil contamination of the silage by rolling grass fields at the beginning of the growing season.