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Racehorse feeding practices and prevention of tying up

Thoroughbred racing and breeding is the largest equine industry in New Zealand, and along with the Standardbred industry, contributes significantly to the country’s economy.

However, around half of all Thoroughbred and Standardbred horses bred don’t make it to a race. While this is mainly due to voluntary trainer decisions associated with poor performance, many are also due to involuntary reasons such as injury or ill health. Much of the data available on these involuntary reasons focusses on musculoskeletal reasons. There is little research available on the number of horses retired due to myopathies such as Recurrent Exertional Rhabdomyolysis (RER), or “tying up”.

RER refers to a specific type of tying up, or muscle cramping, that occurs in response to exercise. Numerous variables including temperament, genetics, and feeding and management practices contribute to the prevalence and severity of the condition – and young female Thoroughbreds and Standardbreds are more frequently affected. Studies have shown that adopting a diet that is low in starch and provides energy through fat and fibre has significant improvements on tying up symptoms. Dietary recommendations are to limit starch sources to less than 20 percent of daily energy and include at least 20 percent of energy requirements as fat for horses in intense work.

To discover the prevalence of trainer identified RER, and to more thoroughly assess feeding and management practices of racehorses with RER in New Zealand, a data collection study was carried out in 2018. Data was collected via a cross-sectional, face-to-face survey of 100 registered Thoroughbred and Standardbred trainers on the number of horses in full work, number displaying signs of RER, gender and age (≤3 or >3 years) of each horse, amount and type of roughage available, weights of all roughage and concentrates added to a standard racehorse diet, turn out time and size of turn out area for both non-RER and RER horses.

The overall crude RER prevalence in New Zealand was 8.4 percent, which is higher than the prevalence found in Thoroughbreds in Australia, the UK and the USA. The study also revealed that a small 7 percent (11/149) of horses displaying signs of RER were provided with dietary starch levels at the recommended less than 20 percent of energy, and average starch levels as a percentage of energy provided to RER horses was 33.4 percent. More RER horses were provided the recommended amount of fat, with 38 percent (56/149) provided dietary fat levels at the recommended more than or equal to 20 percent of energy. However, total average fat levels as a percentage of energy provided to horses displaying signs of RER was lower than the recommendations at 17.5 percent.

While further research in this field is required, the results of this study represent a need for education and a demand for appropriate feeds for RER horses. McMillan Muscle Relieve is a low starch, high fat and fibre racing feed that has been scientifically designed to assist horses with the condition.

For assistance with feeding plans for racehorses to avoid tying up, consult with an experienced Equine Nutritionist.

Article supplied by Luisa Wood, Equine Nutritionist.