Vet on the Moove: Be aware of the risks when co-grazing horses with cattle
Interestingly, co-grazing is a good practice for both ruminants and horses when it comes to parasite control.
Horses and farming have a long harmonious history, and that tradition of horses on farms is certainly alive and well with the number of farmers I met at the Dublin Horse Show.
It made me think about my old pony “Misty” that I had when I was 12 and how she was very much a part of the farm. In my case I saved all my pocket money for my very own pony, it was a dream come true.
I was in the gym a few months ago (yes months) and I was asked by my trainer about any potential risks of co-grazing her aunt's horse with her cattle. Her question, my memories of "Misty" in the calf paddock and the farmers I met at the horse show inspired this particular article.
There is so much talk about mixed species swards, it’s time to talk about mixed species grazing and the risks that need to be kept in mind.
The image of my pony Misty grazing amongst the calves will always be imprinted in my memory, at some points I think she thought she was a calf. Interestingly, co-grazing is a good practice for both ruminants and horses when it comes to parasite control.
They differ in their grazing patterns and the worms do not cross-infect between species. A French study in 2019 showed that horses grazed with cows had reduced egg counts due to the dilution effects of the ruminants eating the equine worm eggs.
The only exception of cross-over parasites is Liver fluke, it can occur in horses, cattle and sheep. Although in horses it is mostly a subclinical disease, it is important to remind your vet of their co-grazing situation if your horse exhibits liver disease.
Routine testing of faecal samples for horses that co-graze is advisable especially in high fluke-risk areas such as wetlands due to higher snail populations, along with the prevention in ruminants.
One co-grazing combination to be aware of is the horse and donkey, equine lungworm can be tolerated much more by the donkey and cross-infection can easily occur. This can be harmful to the horse’s respiratory system, and care with parasite control needs to be taken when grazing both species together.
When co-grazing horses and ruminants it is important to look at what potential poisonous plants or trees are in the fields, some are more dangerous to horses than you may think.
As I drive around the country the yellow hue of ragwort automatically makes me look to see if animals are grazing in the same field. It is one of the most commonly known of poisonous grazing plants and is always on my list of differentials if I see animals with signs of liver failure.
Luckily it has a bitter taste but when wilted and dried into hay it is no longer noticeable and the hay is still palatable. Clinical signs in the horse include weakness, colic, and diarrhoea and can lead to paralysis.
Ragwort causes similar signs in cattle and sheep, however, horses are far more susceptible to its ill effects. When removing from the field it is important to uproot the whole plant and always wear gloves as it can be very irritant to the skin.
This year I noticed an enormous amount of bracken growing in the hedgerows and it can be dangerous to both horses and cattle. It is usually more of a chronic disease that occurs due to regular exposure.
In horses, it can cause weight loss, muscle tremors and seizures. In cows, chronic exposure can cause tumour growth in the bladder leading to red urine and weight loss.
In one of our fields, we have a huge Sycamore tree and luckily I never put Misty in this field as it was too far from her stable. The innocent-looking “helicopter wings” seeds contain a substance called hypoglycin A and they are lethal to horses causing an atypical myopathy.
It is a disorder of the muscular system that can also include muscular organs such as the heart and the diaphragm. Symptoms include sweating, depression, stiffness, tremors, difficulty walking, breathing difficulties, and dark urine.
With early intervention and intensive treatment, they can survive but it is a very serious condition and there is no known antidote. Beware the “Helicopter wings” can live up to their name and travel large distances in the field, so keep horses away completely during the autumn months.
Acorns are another huge risk to horses and, unfortunately, they love the taste of them. Acorns contain tannins which cause acute renal failure and gastrointestinal signs such as severe colic, loss of appetite, and diarrhoea.
Cattle can also be affected by acorn poisoning where they too suffer from renal failure but also show signs of bloat due to ruminal stasis.
If you suspect acorn poisoning please call your vet immediately as this is a true emergency and can be fatal. I remember as a student I saw a case of acorn poisoning in a horse, the vet spotted the oak tress straight away and clicked what was wrong.
Always walk around the perimeter of the field and assess for poison risks. If not grazing the field is not an option, make sure to fence off the risk area beforehand but remember risks like the sycamore helicopters.
Never dispose of lawn clippings or prunings into a field with grazing animals as there is a huge list of garden-based plants that are toxic to both cows and horses e.g. Rhododendrons. If your field is beside a neighbour's garden make sure to inform them of this risk also, they may not be aware.
Another year till my return to the horse show, where that little girl in me wants a pony again, who knows maybe next year.
