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12th December 2005

UK Fertility Survey Results
In the UK, a major study on stud farm efficiency conducted by Professor Twink Allen of the Equine Fertility Unit in Newmarket has found thoroughbred mares “are remarkably fertile despite the fact breeders do not select for fertility,” reported racingpost.co.uk.
“However this fertility, combined with advanced veterinarty techniques, obscures the fact some stallions are nearly sub-fertile.”  Allen noted thoroughbred fertility “is challenged by several entrenched industry practices”, including: not selecting for fertility in mares or stallions; imposing an out-of-phase & artificially shortened breeding season; trying to breed from older mares & stallions; & banning the use of modern technologies such as artificial insemination, embryo transfer and sex selection.  However permitted technologies “such as ultrasound scanning & manipulation of the oestrus cycle with hormones such as prostaglandin, regumate & oxytocin, have greatly increased fertility in mares & this is how we’ve been able to treble the number of mares covered by individual stallions.”  Allen conducted 2 studies: the 1st involving 1,349 flat-bred mares in Newmarket; & the 2nd looking at 2,311 flat mares from Newmarket plus 1,056 jumps mares in Leicestershire & Shropshire.  The studies found mares’ fertility decreases with age: while mares aged 3-8 required an average on only 1.7 matings-per-pregnancy, that figure rose to 2.5 in mares ages 14-18.  Allen reported the placenta of an older mare “is less able to nourish the growing foetus than that of a younger mare” and summed up: “My suggestion is this: we shouldn’t be breeding from these very old mares, no matter how much black-type is in their pedigrees.  We’re simply bashing our heads against a wall trying to get a healthy athlete.”  Allen also reported the fertility of flat stallions in Newmarket “varied considerably, ranging from 43%-96% in terms of conception rate per cycle in the mares they covered; however, teh skill of veterinary surgeons in pin-pointing exactly when mares are ready to be covered mitigates the effect of low fertility in stallions”.
Racing Post Nov 30 2005