It didn’t get off to a good start.  Shoot ‘em, he said. I was talking to an expert, trying to find a solution for Jenny, who wrote asking about a problem she was having.  “I have horses who are grazed rotationally.  I’ve been finding burnt-out patches in the paddocks which I take are caused by their urine.  Any idea of how to deal with this?”

Moving on, I decided it would be good to talk with some horsey people.  Sandra was a horsey person, having kept them since she was a nipper.  She’d never heard of or seen any burnt patches.  Not that she’d looked closely.  I got in touch with a helpful soul at a Waikato horse stud, who for no real reason didn’t want to be named.  She’s never heard of it either and has been involved with horses for the last 20 years. 

“Mind you, with this weather we’ve been having, my home horse paddocks have gone to dust.”

She wondered if the problem was due to something else, like a fungus or parasite. 

“Horses are fussy eaters, they won’t eat weeds.  If you run only horses in your paddocks, they can get ‘horse sick’.  It’s a good idea to run cattle through after the horses, who tend to eat everything and also fertilise the pasture really well.”

My dairy farmer friend said he’d noticed the opposite effect with cows.  “They tend not to really graze where they’ve urinated.  And if the soil is nitrogen deficient, you might get a green spurt of grass in these areas.”

I got on the phone with AgResearch weed scientist Trevor James, who works from the Hamilton campus.

Again, he’d never heard anything relating to burnt pasture and horses but didn’t rule it out.  “It’s quite likely bare patches in paddocks might be caused by horse urine.  If it’s high in nitrogen it well could cause a caustic reaction, ammonia can be pretty toxic on the grass too.

“Horses create bare patches by kicking up the soil and rolling if given the chance.  It’s very difficult to maintain good pasture with horses.”

The dry conditions aggravate the problem – “it’s probably happening now because of the weather.  Plants have no reserves at the moment.”

Often horse paddocks have a lot of weed problems, such as hemlock and dock.  “The best bet is to combat this by running something else with the horse.  Sheep will eat and help keep on top of the weeds.”

Then I came across a tiny item on the net from the Ontario Ministry of Agriculture.  It said that in hot weather, grass and legumes can be scorched and killed by horse urine.

Dog urine, on the other hand, is well known to cause burned patches on lawns.”  It’s more common during drought and high heat.  One piece of advice is to add salt, under veterinary guidance, to the dog’s diet, which makes the dog drink more and dilutes the nitrogen.  You can also buy various products to add to the dogs’ diet or spray on the lawn and – lateral thinking – a can of green spray paint to cover up the patch.

This is obviously no good for someone with a paddock so it was time to call the vet.  Martin Edelmaier works at the Cambridge Equine Hospital and while he’d never come across it with horses, he knew all about it in relation to the canine population.

“You see it more with dogs, especially if they’re on steroids, and more often with females than males.”

This is because females tend to go to the same spot, where dogs rove about and mark trees.  And he had good advice.

“What we say to people is have a look where your dog is urinating to make sure it is the dog and it’s not caused by various lawn diseases.  So, the first thing to do is make sure it is the horse.”

Simply see where the horse is urinating and mark that spot – a can of spray paint would do the job (not green!) and do no harm to the horse.  “And watch what happens.  This is the easy way of telling you what is doing it.”

Normally, he says, horse urine is quite alkaline.  “Some people think it’s the acid in dogs’ urine that causes bar patches but it’s more to do with the nitrogen levels.  Dogs are on high protein diets, while horses generally don’t get too much protein if they’re just out there grazing.”

Then, if it looks like it is the urine, look at what the horse is being fed.  “And is it just one animal, or all of them?  If it’s one animal in particular you can always get the vet to do a blood or urine test to check everything is normal.”

So, Jenny, it sounds like the problem is actually not unheard of with horses, although well documented with dogs.  It well may be the spell of hot weather we’ve just had.  If it does turn out that the bare patches are caused by horse urine, it might have had something to do with the hot weather we’ve just had.  So hopefully it will resolve itself.  In the meantime, grab a can of paint and mark where your horses are relieving themselves.  And let me know how it goes.

Sandra, the horsey friend, sent a text just as I was finishing this.  “Bloody horses.  Broke my leg thoroughly.  In Ward 16.”  Twenty weeks in plaster.  “Shoot them?”  I asked.  “Oh no.  You and I will both go riding in say, oh, 22 weeks.”