The largest worldwide study on X-Rays conducted by the University Of Melbourne has found the most common bone abnormalities revealed in x-rays taken from sales yearlings have no effect on subsequent racing performance, based on number of wins and prize-money earned as 2YOs and 3YOs.
Aushorse Chairman, John Messara, attended last week’s International Breeders’ Meeting where the study was presented and commented; “It just confirms our suspicions that x-ray findings can get in the way of purchasing a proper athlete at yearling sales. It pays to have a qualified vet pass a yearling clinically, rather than buy horses based on x-ray results only.”
Dr Chris Whitton told the veterinary session of the International Breeders’ Meeting in Melbourne: “The bottom line is, radiographic lesions at yearling sales have no or limited effect on future performance.”
The researchers looked at more than 80,000 radiographs taken from over 2,400 yearlings and followed the horses through their 2YO and 3YO careers before drawing their conclusions.
The x-rays examined were held in the repositories at 8 sales conducted by Magic Millions and William Inglis & Son in 2003 (the year repositories, which house yearling radiographs were introduced in Australia). The x-rays included 34 different views of each yearling.
Researchers found 4 types of lesions had “a notable effect on performance”: horses with more severe sagittal ridge OCDs (osteochondritis dissecans lesions) in their hind fetlocks were “10-times less likely to start as a 2YO or 3YO” and “tended to make their debuts later and have slightly fewer starts.” However researchers found no difference in the number of wins and prize-money earned by these horses significantly, Dr Whitton explained; “My reading is that these horses are slower to mature.”
Horses with any OCD lesion of the stifle “performed at a slightly lower rate;” so did horses with a bone formation on their front sesamoid. However the effect was small enough that “it’s hard to get excited about them”, concluded Dr Whitton. There were 8 types of lesions that had no effect on performance “including bony fragments in the fetlock and sesamoid fractures”, added Whitton.
Dr Whitton concluded: “If you see changes in yearlings, they don’t seem to affect performance.” He added it was likely that yearlings with more serious problems were either treated before the sale or not entered, reducing the likelihood of career-threatening defects appearing in yearlings at auction.
In December 2006 Aushorse released a comprehensive booklet based on the US experience exploring OCDs in sale horses.
Extract from Aushorse