Research confirms effectiveness of grazing muzzles

Using a grazing muzzle appears to be more effective than restricting access to pasture, for reducing the amount of grass eaten by ponies, according to a recent study.

Pasture intake by the ponies grazing for three hours without muzzles averaged 0.8% (with some eating close to 1%) of their bodyweight, which is the equivalent of up to two thirds of the recommended daily dry matter intake  for many ponies on restricted diets.

In contrast, the pasture intake of the ponies when wearing muzzles was around 0.14% of bodyweight over three hours, representing an average reduction of 83% compared to when they were not wearing muzzles.

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Making sense of flexion tests

Flexion tests are often used as part of a prepurchase examination or a lameness work-up to evaluate lameness or assess the likelihood of future lameness problems. But what does a positive flexion test tell us about which structures are involved?

Research published in the Equine Veterinary Journal suggests that the fetlock is probably responsible for a positive response to flexion test of the lower limb. Structures below that joint are less likely to be involved.

Dr Clodagh Kearney and colleagues conducted a study on eight warmblood horses. These were all clinically sound, but had gone lame after being subjected to a flexion test of the lower limb. Flexion tests were performed under standardised conditions.

The response to the flexion test was assessed after performing various nerve blocks, which desensitised different regions of the limb. One clinician performed the nerve blocks; others performed the flexion tests and assessed the degree of lameness. So the clinicians assessing the lameness did not know which nerve block had been carried out (or on which leg).

They found that a nerve block of the palmar digital nerves, just above the cartilage of the distal phalanx, had minimal effect on the lameness induced by the flexion test. A nerve block just below the fetlock at the level of the distal abaxial sesamoid bones produced a similar response. However, there was a marked improvement in flexion test induced lameness following a low four point block just above the fetlock.

The researchers conclude that the fetlock joint and surrounding structures contribute strongly to the outcome of a flexion test of the lower limb in a non lame horse. "From a clinical point of view, it is reasonable to suggest that the flexion test of the distal limb may be sensitive for investigating the metacarpophalangeal joint region, but may be less relevant for structures distal to this joint."

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Treponemes found in canker lesions

Japanese research has found evidence of treponemes in equine canker by looking for specific portions of RNA characteristic for the organisms.

Canker is a chronic proliferative condition of the horse's foot - affecting the frog and bars and sole. In severe cases it may extend to involve the hoof wall. Similar conditions in cattle and sheep have been shown to be associated with spirochete bacteria - in particular treponemes.

Dr Kyaw Kyaw Moe and colleagues examined samples from lesions in two horses and compared them with samples from an unaffected horse.

They found spirochetes in microscopic sections of the canker lesions. They also found 114 clones in the affected horse samples and none in samples from normal horses.

The clones could be classified into 19 separate groups - corresponding to many different treponemes, including those implicated in bovine papillomatous digital dermatitis.

Despite this the researchers were unable to culture the organisms. This is not surprising as treponemes are slow growing and are often overgrown by more rapidly growing bacteria.

The research confirmed the presence of treponemes in canker lesions in two horses and their absence in a normal horse. However, as the study was based on only a couple of cases, the researchers could not confirm that treponemes are the cause of canker - further work is required involving more cases.

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Effect of psyllium on glucose and insulin

Psyllium, a sort of "super-bran", is already used in horses, particularly for treatment and prevention of sand colic. When mixed with water, it swells to up to 10 times its original volume, turning into a jelly-like substance which is thought to ease the passage of sand through the digestive tract.

Researchers at Montana State University conducted a trial to see if adding psyllium to a horse's diet had an effect on glucose and insulin metabolism. It had been noticed previously that psyllium had a beneficial effect on insulin sensitivity, when taken by people with insulin resistance. So they wanted to investigate whether a similar effect occurred in horses.

They used 16 healthy horses (8 mares and 8 geldings), which they divided into 4 groups of 4, each containing 2 mares and 2 geldings. All horses were fed a diet of mixed grass hay and a commercial whole grain feed twice a day. Psyllium pellets were added to the grain ration of three groups at 90g, 180g, or 270g daily. The fourth group received the same diet, but without added psyllium.

On the 60th day the researchers withheld food from the horses overnight. In the morning they collected blood samples before the morning feed and then every 30 minutes for six hours, to monitor the blood glucose and insulin concentrations.

The researchers found that on average, horses that had been receiving psyllium for 60 days had lower average peak glucose levels after feeding and lower average glucose levels. Psyllium-fed horses also had lower peak insulin levels and lower average insulin levels after feeding compared with horses that had not received psyllium.

Dr Shannon John J Moreaux, Assistant professor of Equine Science at Montana State University, and one of the research team commented. "Psyllium could be especially beneficial to obese, insulin-resistant horses, or horses that are predisposed to developing laminitis because of metabolic syndrome". He added that it was commercially marketed and readily available to horse owners, and when fed daily, may help to maintain lower post-feeding blood glucose and insulin levels.

This was a small study carried out using normal horses. Before we can conclude that psyllium will benefit insulin resistant horses, further research is needed using affected horses.

However, if it proves to be effective in insulin resistant horses it could provide a useful addition to the strategies available for managing this condition.

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