4th Australasian Equine Science Symposium 2012

The 4th Australasian Equine Science Symposium was held from 13th to 15th  of June on the Gold Coast. QLD.  The theme of this years’ symposium was “research for the 21st century horse industry; from genetics to the winning post”

Since 2006 the symposium has been organised biennially with the objective to provide a forum for the exchange of research findings, ideas and information between Australian, New Zealand and other international researchers. The symposium focuses on science, technology and innovation relevant to the Australian horse industry. It promotes excellence in equine science, assists young researchers with their careers and encourages participation from interested horse industry people such as horse owners, trainer and breeders.

Researchers from Australia, NZ, UK, and USA presented a number of papers. There were 12 invited papers and 47 contributed papers divided into 8 subjects; carbohydrates and metabolism, musculoskeletal development and injury, genes, research and Hendra, nutrition, body condition and health, disease and disease control, equine education and therapeutics, reproduction and management and caterpillars and foetal loss.

A brief summary of a selection of papers will be described below – for a more detailed report see the AESS abstract. The proceedings with the listed abstracts can be downloaded from the AESS (http://www.australasianequinescience.com).

Carbohydrate & Metabolism

The prevalence of overweight or obesity has increased considerably in humans as well as companion animals including horses. The reasons that domesticated animals develop obesity are generally similar to those reasons that have been attributed to obesity in humans.  Modern-day husbandry practices are characterised by the imbalances between energy intake (energy-rich feeds) and energy expenditure (inactive horses). In humans, obesity is associated with Insulin resistance (IR), type-2 diabetes and cardiovascular diseases. In horses we also encounter IR, but rarely the other disorders. It is important to realise that obesity can cause IR, but not all IR horses are obese, it can occur in thin horses as well. However, in horses IR has been linked to other specific disorders, such as laminitis, hyperlipemia (hepatic lipidosis), developmental orthopedic disease (osteochondrosis) and pituitary pars intermedia dysfunction (equine Cushing’s syndrome).  IR is a condition in which normal amounts of insulin fail to maintain normal blood glucose because of decreased responsiveness of muscle (glucose uptake), liver (inhibition of gluconeogenesis) and fat cells (inhibition of lipolysis).

That obesity doesn’t necessarily have to cause IR was also supported by one of the contributing papers of the AESS.  Mr. Bamford (Vet Sci student from the Melbourne University) and colleagues looked at the effect of increasing adiposity  (fat deposits) on insulin sensitivity in horses and ponies.  They used 6 adult Standardbred horses, 6 mixed breed ponies and 6 Andalusian-cross horses in their study and two horses of each breed were assigned to one of the three different diets they tested.  The groups of horses were offered a high fat diet (FAT; that was supplemented with vegetable fat/oil), high fat diet +glucose (FAS; to cause a glycaemic and insulinaemic response) and a basal diet with no supplementation (CON). The study period lasted for 21 weeks and they measured the percentage of body fat, body condition score (BCS) and insulin sensitivity (IS) over this time.  The horses from both the FAT and FAS group had a significant increase in percentage of body fat and BCS, while the CON remained unchanged. They also found that the IS did not change significantly in the FAT and CON group, but there was a significant improvement in the SI in the FAS group. The authors suggest that increasing adiposity alone did not cause IR, when animals are fed a high fat, low glycaemic diet.  This has also been seen in humans, not all obese people have IR or diabetes, as not all fat depots contribute to this disease. In human studies they discovered that fat distribution in the body is important for the progress of the disease. Thus, abdominal fat is more important in relation to IR than subcutaneous fat and the reduction in abdominal fat can increase the sensitivity of insulin in humans. This something that is not very clear yet in horses. But the current study did show that short-term glucose/insulin peaks might slightly improve insulin effectiveness in horses. Nevertheless, careful dietary changes have to be made and must go hand in hand with an exercise program to reduce adiposity as obesity may remain a risk factor for horses independent of IR.

Research & Hendra

Also this year there were some papers and updates on Hendra. In particular the status of the Hendra virus vaccine for humans and horses was discussed.

Another paper that was presented was on pasture availability and the influence of Hendra virus infection of grazing horses. This got some media attention because they suggested that hungry horses could be more susceptible to contracting Hendra virus.

Just some background – HeV is a member of the Henipavirus. Fruit bats or flying foxes (genus Pteropus) are carriers of HeV. Researchers assume that HeV is transmitted from bat-to-horse through the ingestion of infected objects such as fruit, spats and other feed or water sources contaminated with urine, faeces etc. Still, there is a lot of information missing about the progress of the disease, in particular what was the management prior and up to disease occurrence and in what environment where these horses kept i.e. property aspects, horse facilities and design, topography, pasture cover, vegetation, key horse behaviour etc.

Mr. Anderson (Bahrinna Thoroughbred Services) & Prof. Bryden (University of Queensland) collected data from the locations of the HeV infection sites and looked at local climatic conditions prior to infections and assessed the likely forage availability and pasture dynamics in 2011.  The preliminary data showed that Hendra incidences in SEQ/NrthNSW occurred primarily during the non-growing season (June-Oct) when there was low dry matter production. This would significantly reduce the nutrient intake for pastured horses and if not supplemented adequately horse behaviour may be influenced as well as the wellbeing. Stress (of not finding enough foods) may have negative impact on the immune system, making horses more vulnerable for infection. In addition, in the search of more forage, horses may show higher incidence of browsing as well as grazing closer to the ground. The authors showed that some of the pastures where HeV infection occurred where overgrazed with limited biomass left. This may set the scene that horses may encounter and ingest bat related materials in their paddocks. Horses are designed to graze and browse for up to 16h per day, when we are not providing these opportunities the behaviour of horses will be altered. These findings and suggestion are very preliminary, more in-depth research is required to gain some insight into these risk factors. Even healthy well-fed horses that show a curiosity for new edible things may as well ingest bat related material. So don’t start excessively overfeeding your horses during non-growing seasons as you can read above it may create obese horses – another issue we want to avoid!

Nutrition & Health

As already mentioned above foraging and feeding behaviour comprises a large part of the time budget of horses. We are all aware of that horses are grazing herbivores but they also eat a substantial amount of browse (up to 50% of the total diet).  I have been addressing foraging behaviour in earlier articles in the Horses and People Magazine, and this year I was able to present my PhD proposal on this topic at the AESS. As part of this study Mrs Triebe, an honours student from University of New England, examined 2 novel forages (browse) with the aim to determining the preferred forage and to examine the variability in preference exhibited between individual horses. Horse preference for Tagasaste (Chamaecytisus palmensis) and Golden Bamboo (Phyllostachys aurea) was tested on each of 3 consecutive days on 12 properties (20 horses –more testing is currently undertaken). The preliminary results indicated an initial preference for Tagasaste on day 1 followed by a greater preference for Bamboo by day 3. These findings suggest that 3 days of consecutive testing appears to be sufficient time for horses to initiate a postingestive feedback to the novel forages. Future research will further develop this forage preference testing methodology and will test other novel forages (identified through literature review and a horse industry survey).

At first instance horse owners may be a bit wary of using novel forages (browse) as alternative forage and enrichment as they think that having shrubs and trees may be a risk for bat material to land on. However, this may also be the case with your pastures – when bats fly over and drop their spats, urine or faeces. The good thing about browse is that you can use it as a cut-and-carry system. You can carefully wash the browse and provide it under sheltered areas in tubes – a good way to provide horses with more fresh forages especially during the non-growing season or drought.

Bamford, N.J., Potter, S.J., Harris, P.A., and Bailey, S.R. 2012. Effect of increasing adiposity, induced by a high fat low glycaemic diet or similair diet with once daily glucose, on insulin sensitivity in horses and ponies. Proceedings of the Australasian Equine Science Symposium 4; 19.

Anderson, D.L. & Bryden, W.L. 2012. Does pasture availability influence Hendra virus infection of grazing horses? Proceedings of the Australasian Equine Science Symposium 4; 34-35.

Triebe, C., Van den Berg, M. and Brown, W.Y. 2012. Tagasaste versus bamboo: which do horses prefer? Proceedings of the Australasian Equine Science Symposium 4; 41.

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