The feeding and management of Thoroughbred and Standardbred Racehorses displaying clinical signs of Recurrent Exertional Rhabdomyolysis

Data on the feeding and management of racehorses and the prevalence of trainer identified Recurrent Exertional Rhabdomyolysis (RER) were collected via a cross sectional face-to-face survey of 100 registered Thoroughbred and Standardbred trainers (n= 1,771 horses) in New Zealand. Data were collected 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, turn out time and size of turn out area for both non RER and RER horses. The overall crude RER prevalence was 8.4% (95% CI 7.2-10.8) with no significant difference in prevalence between breeds. Premixed feeds were fed to 98% (1,742/1,771) of the total population, and 99% (148/149) of the horses that displayed signs of RER. Most RER horses had additional ingredients included with the premixes (58%; 86/148), with 65% (56/86) receiving additional grain, 59% (51/86) receiving added fat, and 24% (21/86) receiving both grain and fat. Feeds specially formulated for horses that “tie-up” were fed to 50% (75/149) of horses displaying RER signs. However, 64% (48/75) of these horses had additional grain or a standard racing feed also included in the diet. Average starch levels (% of DE) provided to horses displaying signs of RER were 33.4±1.1%, and only 7% (11/149) of horses displaying signs of RER were provided with dietary starch levels at the recommended less than 20% of energy. Average fat levels (% of DE) provided to horses displaying signs of RER were 17.5±0.6%, and 38% (56/149) of horses were provided with dietary fat levels at the recommended ≥ 20% of energy.