In late November last year, on an otherwise quiet weekend on duty I received a rather alarming call out during the middle of afternoon milking for multiple cows down on the yard and race. Any herd level event with collapsed cows is considered a high priority emergency, and is often associated with feed or toxicity.

Upon arrival I found the shed was going, and cows were walking out the exit race without much fuss, but they appeared twitchy and stiff legged. Cows rowed up for milking appeared fine from a distance, but on closer inspection had a subtle head bob that worsened when they turned their heads towatch me. The herd had been absolutely fine in the morning, but in trying to get them to the shed this afternoon some would intermittently fall over on the race and be unable to rise. The same happened on the yard when the backing gate was put on, or when cows pushed to exit the shed. If left alone for long enough the down cows would eventually rise under their own steam and carry on like nothing had happened.

All of this together indicates a simple, but frustrating disease we more commonly see in calves – Ryegrass staggers. Not to be confused with grass staggers (which is caused by low magnesium) ryegrass staggers is caused by a toxin called Lolitrem B, and is characterised by an intention induced tremor. This means that the faster an animal tries to move, the worse the tremors become, but an animal standing still in a paddock will have next to no clinical signs of the disease.

Lolitrem B is produced by a fungal endophyte in many ryegrass pastures. The endophyte is included to reduce insect damage to growing pasture, and the toxin it produces is most highly concentrated in the base of the leaf sheath and in the flower heads. The toxin has no long lasting effecton the nervous system, and once removed from the unsafe pasture cows will return to normal fairly quickly. Most of the damage to stock with this disease process comes from misadventure – animals fall into drains or fences and are unable to get out.

Unfortunately, there is also no easy fix for ryegrass staggers except for removing the source of exposure, which is difficult in a pasture-based system! Affected animals should be moved to new pasture and should not be allowed to graze close to the base of the sward. Increasing the supplement on offer will reduce the amount of pasture eaten.

In any affected mob, move animals slowly and gently, and plan for longer milking and walking times. Frustration is never a good mix with moving stock, but with ryegrass staggers in particular it will only make the ob harder. If cows go down, especially on concrete, the best option is to move away, leave them undisturbed, and allow them to rise in their own time.