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VET CLINIC

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AMMONIA RISKS, VET NEWS

WINTER COATSWHEN a horse or pony’s finer and shorter summer coat hairs are replaced by longer, thicker winter hairs, it provides warmth when the seasonal temperature is lower. Once the winter coat is grown, it tends to look more unkempt and dishevelled until it is shed in spring.

Scientists in Poland took 12 warmblood geldings and 12 Felinski ponies, which are quite fine ponies. They divided them into two groups, six of each breed in each, and kept them from December to May in two different stable blocks. One block had an average air temperature that ranged from 7.5°C to 9°C over 24 hours, the other an average of 4°C to 7.5°C.

The animals were out in paddocks for two hours daily then stabled on straw and fed identically. At regular intervals the scientists collected and measured hair from various sites: the shoulder, sternum, back and belly.

Hair continued to grow in length right through from December to May and its length was strongly correlated with air temperature. The warmbloods showed less difference between the two stable blocks than the ponies did and the hair on their backs hardly grew at all — even in the colder stables. The ponies showed adaptation to colder stables across their body and to a greater extent.

The group that had been stabled in colder air shed their winter coat about three weeks earlier than the group in the warmer stables. The longer, thicker coat generated in response to the cold was making them too warm when the weather started improving.

STRESS ON THE STREETS?VETS in New York have investigated whether the carriage horses that take visitors on rides around the city centre, including Central Park, are suffering from unreasonable stress.

Cortisol in saliva is a reliable indicator of very recent stress; cortisol in dung gives a good idea of average stress over the previous 24 hours and eyeball temperature shows whether the horse is currently distressed. The vets measured these parameters in 13 carriage horses at work in the city and also in five New York carriage horses turned away at pasture in Pennsylvania. The study was undertaken in August when heat, fumes, noise and city-centre clamour were at their worst.

Surprisingly, there was no difference in the dung cortisol between the horses at work and those on holiday, indicating that the working horses were not suffering chronic stress. The eyeball temperature of the working horses only rose in line with the ambient temperature of the hot summer days. The salivary cortisol was only slightly elevated after the jog back to the stables in the evening, not by the daytime work — a normal response to increased exercise.

By all measurements, the carriage horses seem to be like human New Yorkers — laid-back and unflustered by the hubbub of city centre life. H&H

• NEXT WEEK: hock fusion

WHAT’S NEW in the veterinary world?From coat growth to stress experienced by carriage horses — Peter Green MRCVS highlights the latest in scientific research

Sniffing out a problemAn eye-watering odour in the stable could point to high levels of ammonia — with associated health risks. Andrea Oakes reports

THE pungent smell that can burn your nostrils and throat as you muck out is ammonia, a colourless gas

produced by degrading urine. Dr Kieran O’Brien of Penbode

Equine Vets in Devon explains that a horse urinates five to eight times a day, producing around 15 litres — the equivalent of a large bucketful. Bacteria present in droppings, in soiled bedding and on the stable floor convert the urea within urine into ammonia gas.

“The trend for using rubber stable matting with minimal bedding means that urine can become trapped underneath the mats, where it stagnates and releases ammonia,” he says. “High ammonia levels can irritate the horse’s respiratory system and cause inflammation and excess mucus production, which can interfere with oxygen uptake as he works.

“Foals are especially at risk as

they spend a lot of time asleep with their head at floor level,” he adds. “Ammonia in the bedding is also known to damage horses’ feet, predisposing them to thrush and white line disease.

“The Health and Safety Executive has set the maximum permitted eight-hour workplace exposure ammonia level for people at 25ppm (parts per million), yet the level in stables can be as high as 250ppm or more. If you can clearly smell ammonia in the stable or on your clothes, the level is likely to be at least 100ppm. Some stabled horses are forced to breathe this for up to 23 hours per day.”

The solution is two-fold: to decrease ammonia production and to allow adequate ventilation to dilute the level in stable air. Kieran adds that horses can be taught to urinate on command and the urine caught in a long-handled muck scoop. One way is habituating a horse with a certain sound (for

The VetPENBODE Equine Vets provides care for horses throughout Cornwall and Devon. This independent, XL Equine practice, offers the complete stableside service with the back up of extensively equipped clinics at Holsworthy and Tavistock. penbodevets.co.uk

7 STEPS TO CLEAR THE AIRTo reduce ammonia levels, Kieran recommends:

1 Use more bedding. A thick layer, spread over a wider

area, will absorb urine run-off and allow more complete removal. Soft rubber mats are sometimes associated with unacceptably high ammonia levels. A sloping floor with a channel should allow urine to run away, but the low volume passed means this tends not to happen.

2 Use absorbent materials. Finer bedding materials

such as sawdust (from pellets) and shavings result in the smallest urine footprint, though sawdust can work into the gaps between the mats and cause them to lift and separate. If you use straw, use a more absorbent alternative underneath. Remove as much soiled bedding as possible at least twice a day.

3 Muck out when the stable is empty. Exposing the wet

bedding and floor will raise the ammonia level. Leave the stable empty afterwards, preferably with the door open.

4 Use a stable disinfectant. If the bedding is pushed

back every day, sprinkle the urine footprint with powdered (not granular) garden lime, or a powdered stable disinfectant, both of which inhibit the action of the bacteria.

5 Seal between mats. Lifting mats and

disinfecting underneath is an onerous task that’s rarely done often enough; liquid disinfectant such as Virkon can be brushed into the cracks as a stop-gap measure.

6 Reduce protein. Protein fed to excess results in

more urea being excreted in the urine and consequently more ammonia production.

7 Improve ventilation. Every stable should have two air

inlets/outlets. Removing window glass, opening doors and using a door chain will improve airflow and dilute the ammonia level.

example whistling) every time the horse urinates. Once this command is learnt he can be taken to an area of a paddock where he has urinated before and urination induced.

“They soon learn that is why they have been taken to that place and will often urinate without being asked,” says Kieran.

“Alternatively, use the reluctance to urinate on bare floor to your advantage. Stand your horse on a bare floor for an hour or so, for example when being fed, after bringing him in from the field. Then scatter bedding and catch any urine that is passed.” H&H

Pees and q’s: horses urinate up to eight times a day, producing the equivalent of a large bucketful of urine. Use thick layers of fine bedding such as sawdust or shavings to reduce ammonia levels, and muck out as often as possible

Further readingHair growth: Animal Science Journal (2017) 88, 339-346Carriage horses: JAVMA (2017) 316-321