Australasian Equine Science Symposium 2010

By Mariette van den Berg BAppSc. (Hons), MSc. (Equine Nutrition) www.mberg.com.au

The third Australian (renamed Australasian) Equine Science Symposium (AESS) was held on the Gold Coast, Queensland from June 3-5, 2010. 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 5 invited papers and 53 contributed papers divided in 9 themes; foetal loss, caterpillars and placentitis, reproduction efficiency, foal care and infectious disease, vitamin and lipid metabolism, nutrition and insulin sensitivity, nutrition, management and the environment, OCD and musculoskeletal injury, therapeutics and drug testing and Hendra virus infection.

A summary of a selection of papers will be described below. The abstracts of the presented papers are all listed on the website of the AESS (www.australasianequinescience.com)

Foetal loss, caterpillars and placentitis

In 2004 a number of abortions in mares were reported from Thoroughbred studs in the Hunter Valley region of New South Wales. The condition was named equine amnionitis and foetal loss (EAFL). EAFL cases showed an unusual and constituent pattern of clinical and pathological signs including; inflammation of the placental membranes and bacterial infections. EAFL has similar description of abortions as seen with Mare Reproductive Loss Syndrome (MRLS), which was first described in 2001 in Kentucy, USA. MRSL is linked with the exposure of pregnant mares to Eastern Tent caterpillars (Malacosoma americanum). In Australia, a similar hairy caterpillar, processionary caterpillar (Ochrogaster lunifer), was found in large numbers on various studs and farms where EAFL abortions were diagnosed.

A series of experiments were conducted to determine if caterpillars were the cause of the abortions seen on the farms. The results of the experiments show that whole processionary caterpillars as well as shed exoskeleton can induce EAFL in pregnant mares. The caterpillar’s setae (bristle or hair structure) causes a wide spread inflammatory reaction in the digestive system and body of the mare which may result in abortion.

Current research is focussing on understanding the role of the caterpillar’s setae and possible toxins in the development of EAFL and designing an animal model for EAFL as an alternative to using pregnant mares. You can find more information about this research on the RIRDC website (http://www.rirdc.gov.au  publication no. 09/155).

Nutrition and insulin sensitivity

A number of speakers from Australia, USA and UK talked about a more common problem in horses; insulin resistance and obesity.

One of the studies looked at glycemic/insulinaemic response to feeding hay with high and low non-structural carbohydrates (NSC) content in horses with Polysaccaride Storage Myopathy (PSSM). The results showed that horses that were fed high carbohydrate hay had a higher insulin response compared to horses that were fed medium and low carbohydrate hay. PSSM horses had lower insulin responses to high carbohydrate hay than healthy control horses. This outcome is consistent with higher insulin sensitivity in PSSM horses. However results may have been influenced by higher palatability and more rapid intake of high carbohydrate hay, which may increase insulin response and glucose uptake after feeding of the hay. They suggest that feeding hay with an NSC >17% to horses with PSSM or conditions related to insulin resistance should be avoided and that hay with an NCS <11% is considered safe.

psyllium husks

Another study from the USA looked at the effect of Psyllium on blood glucose and insulin concentrations in horses. Psyllium (seed husks) is a dietary fibre that is used in humans for controlling diabetes. The metabolic effects of feeding Psyllium daily to horses are unknown and hence this study. Sixteen normal, non-obese and unexercised horses were used in the experiment. Three levels of Psyllium (90g/day, 180g/day and 270g/day) were fed with a twice daily grain and hay ration for 60 days.  Glucose levels were significantly lower at 90 and 120 minutes after feeding in horses that received Psyllium compared to the control horses. Insulin concentrations were significantly lower at 90 min and 300 min after feeding in horses fed Psyllium compared to horses that didn’t receive treatment. The results showed that all three levels of Psyllium caused a similar response. The findings suggest that Psyllium may benefit horses that have insulin resistance or are prone to developing laminitis. Further research is needed to confirm the beneficial effects in this group of horses.

OCD and musculoskeletal injury

One of the keynote speakers was Professor Sarah Ralston, from the Rutgers University in the USA. She spoke about genomics (study of an organism’s hereditary information; DNA profile) and developmental orthopaedic disease. The study she presented focussed on understanding the different metabolic profiles of horses that have Osteochondrosis dessicans (OCD) and horses that don’t. By metabonomic analyses of the Nuclear Magnetic Resonance (NMR) spectra of blood serum samples they revealed clustering due to repeatable differences in metabolic profiles of horses that had OCD and those that didn’t. These results suggest that you may be able to indentify metabolic pathways in genetically predisposed foals and detect foals at risk before OCD lesions appear. Further studies are undertaken to determine this possibility.

Hendra virus infection

Due to the resent new outbreak of Hendra virus (HeV), there was a big interest in the latest information and research on HeV. Professor Nigel Perkins presented an overview of the HeV and discussed changing behaviour to manage Hendra risks. Principal Biosecurity officer Fiona Thompson presented the latest information about biosecurity and risk management for horse properties and events.  Dr. David Lovelle from the Redlands veterinary Clinic shared his personal experiences with HeV when the clinic was stricken by an outbreak of HeV in August 2008.

HeV is a member of the Henipavirus. Fruit bats or flying foxes (genus Pteropus) are carriers of HeV. Flying foxes live in large groups and roost on tree branches. Due to changes in their ecosystem, flying foxes populations are declining and form smaller more dynamic populations which makes them more common in pre-urban areas. Transmission of the HeV occurs through infected foetal fluid, placenta, urine, faeces and saliva. The potential pathways are from bat-to-bat and from bat-to-horse (or other animals). 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.  Horse-to-horse and human assisted transmission may have also occurred in those cases where more horses at one locations where kept.  The transmission from horse-to-human is not known. Human cases of HeV had direct and close contact with horses that were infected. Close contact with mucous membranes of infected horses may be associated. The incubation time (time from exposure to appearance of first clinical signs of disease) in horses is 5 to 16 days. This means that infected horses that don’t show signs of the disease yet can potentially shred the virus. This is an important aspect and supports that PPE (personal protective equipment) and biosecurity measures may be effective in minimising or preventing exposure to HeV when people interact with horses that may be infected.

HeV is susceptible to a wide range of disinfectants and detergents. Simple hygiene procedures as hand washing and disinfection are effective in destroying the virus. HeV is killed when exposed to direct sunlight, but can survive for couple of days under optimal conditions (moist fruit juice, bat urine in moist areas without sunlight).

Ongoing research is focusing on the transmission of the HeV through various pathways and development of vaccines and other therapeutic options for horses and humans. More information about HeV and biosecurity measures can be found on Biosecurity Queensland website (http://www.dpi.qld.gov.au) and on the Queensland Horse Council website (http://www.qldhorsecouncil.com).

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