Thursday, March 28, 2019

Study confirms exercise benefit for dieting horses

New research has shown that even 25 minutes of light exercise may benefit your horse’s health, even if it doesn’t result in additional weight loss.

The study was carried out by Nick Bamford and his colleagues at the University of Melbourne’s Faculty of Veterinary and Agricultural Science, in collaboration with SPILLERS®. An abstract of the research has been published in the Journal of Veterinary Internal Medicine.

A total of 24 obese horses and ponies were randomly divided into two groups; ‘restricted diet only’ or ‘restricted diet plus exercise’. All horses and ponies were fed the same diet of restricted hay at 1.25% body weight on a dry matter basis (no grazing), a small amount of alfalfa chaff and soya bean meal, and a vitamin and mineral supplement. 

The exercise programme, which was designed following feedback from horse owners to help ensure it could be implemented relatively easily in ‘the real world’, consisted of 15 minutes of brisk trotting (with a five-minute walk before and after) five days per week for 12 weeks.

The ‘restricted diet only’ group showed an overall reduction in body weight and body condition score. They had increased levels of adiponectin – a hormone produced by fat cells, low levels of which are a risk factor for laminitis. They had decreased baseline insulin, high levels of which have been linked to an increased risk of laminitis, and decreased leptin, high levels of which are associated with obesity.

Although exercise did not increase weight loss, it did produce additional benefits that were not seen in the ‘restricted diet only’ group, the most important one being improved insulin sensitivity. This is important because high levels of insulin in the blood and/or reduced insulin sensitivity are risk factors for laminitis. Horses and ponies in the exercise group also had decreased levels of ‘serum amyloid A’, a protein that is a marker for inflammation.

“Reducing calorie intake and feeding a diet low in starch and sugar should be the priority for overweight horses and ponies,” said Clare Barfoot RNutr, the research and development manager at SPILLERS®. “However, the results of this study suggest that exercise may offer additional health benefits for obese horses and ponies and/or those with ‘EMS’ that cannot be achieved by cutting calories and weight loss alone.”

She added that the exact amount of exercise required is yet to be established – even if you are unable to follow the exercise programme used in this study, some exercise may still be beneficial.

For more details, see:

Influence of dietary restriction and low-intensity exercise on weight loss and insulin sensitivity in obese equids.
Bamford NJ, Potter SJ, Baskerville CL, Harris PA, Bailey SR.
J Vet Intern Med. (2019) 33:280-286.

Donkeys may provide new tick repellent

A possible new tick repellent has been isolated from donkey sebum (the oily substance secreted by sebaceous glands to keep skin moisturised.)

Amblyomma sculptum, a species of tick found in South America, feeds on animals and humans. It is an important vector of Rickettsia rickettsii, the agent responsible for Brazilian Spotted Fever (Rocky Mountain Spotted Fever in USA) - the most lethal tick-borne pathogen affecting humans.

The horse is a common host for the tick, and although horses may have antibodies to R rickettsii, clinical signs of disease are rare.

Unlike horses, donkeys are resistant to the tick. Researchers at the Federal University of Goiás, Brazil, working with colleagues at the Rothamsted Research in the United Kingdom have been investigating whether this could be due to differences in the secretions of the sebaceous glands in the skin of horses and donkeys.

The researchers collected sebum from donkeys and horses and isolated the volatile compounds it contained. They found five compounds, present in differing proportions in horses and donkeys. However, one compound, ((E)-2-octenal), was found only in donkey extracts and not in horse extracts.

Further tests were carried out with this compound using a Y-tube olfactometer, a technique commonly used in chemical ecology research. A. sculptum nymphs were given the choice between two odour sources to test behavioural preferences,

The research team found that the dry sebum extracts and the five compounds identified in both horses and donkeys had neither attractant nor repellent effects.

Only (E)-2-octenal, the compound found only in donkey sebum, showed a repellent effect. More nymphs preferred the arm containing the solvent control than the test arm.

The researchers report than “even a combination of ammonia (which attracts ticks) and (E)-2-octenal at 0.25M also resulted in preference for the control arm.”

The authors suggest that (E)-2-octenal could be used as a repellent to interfere with ticks locating their host and to help reduce A. sculptum numbers on animal and human hosts.

For more details, see:

Identification of a non-host semiochemical from tick-resistant donkeys (Equus asinus) against Amblyomma sculptum ticks.
Ferreira LL, Sarria ALF, de Oliveira Filho JG, de Silva FO, Powers SJ, Caulfield JC, Pickett JA, Birkett MA, Borges LMF.
Ticks Tick Borne Dis. 2019 Feb 16. pii: S1877-959X(18)30414-X.

Strongylus vulgaris wild horse reservoir

Wild horse populations may act as a source of infection for domestic horses, according to a recent report.

Strongylus vulgaris, (also known as the blood worm) is the cause of verminous endarteritis. The larvae migrate from the horse’s intestines into the surrounding blood vessels and continue to various organs around the body, causing damage as they go.  The resulting thrombi can block blood flow and result in tissue damage and colic.

The parasite has been well controlled by macrocyclic lactones – so much so that from being the most important equine parasite of 30 years ago it is now rarely a problem in domestic horses.

Researchers from the University of Sydney and the University of Tasmania examined 289 faecal samples collected from six separate wild horse herds in south east Australia.

Andrea Harvey and colleagues found a wide range of total strongyle egg counts (ie both “large” strongyles such as S vulgaris and “small” strongyles – such as the cyathostomins) Eggs of large and small strongyles look the same. Appearance cannot be used to differentiate between Strongylus vulgaris and other strongyle-type eggs.

Most of the faecal samples contained S vulgaris DNA. The research team report: “A high prevalence of S. vulgaris DNA in faecal samples was demonstrated across all six populations, with an overall predicted prevalence of 96.7%.”

Over 89% of samples had more than 500 eggs per gram, classing them as “high shedders”.

The researchers suggest that vigilance is required when adopting wild horses, and when domestic horses graze in on land also grazed by wild horses. 

They advise that it would be wise to monitor horses for S. vulgaris using larval culture or DNA testing.

But it's not all bad news. The population of worms in the wild horses also acts as a reservoir of small strongyles that have not been exposed repeatedly to anthelmintics and may be able to play a role in management of anthelmintic resistance.

For more details, see:

Wild horse populations in south-east Australia have a high prevalence of Strongylus vulgaris and may act as a reservoir of infection for domestic horses
Andrea M.Harvey, Maira N.Meggiolaro, Evelyn Hall, Ellyssia T.Watts, Daniel Ramp, Jan Šlapeta
International Journal for Parasitology: Parasites and Wildlife. (2019) Vol 8, pp 156-163