Study links inbreeding and pregnancy loss in horses
7 Apr 2024
Mid and late term pregnancy loss among thoroughbred horses appears to correlate significantly with the prevalence of inbreeding, according a Royal Veterinary College study.
Inbreeding, a common practice in the livestock industry aimed at perpetuating traits regarded as desirable by breeders and purchasers, has long been recognised as a potential risk factor for genetic anomalies. It is known to increase the probability of uncovering homozygous recessive genotypes which have previously been associated with an increased risk of retained placenta and lower semen quality in horses.
However, the RVC research, undertaken in collaboration with the US Cornell University is the first to identify its specific impact on equine pregnancy loss. This occurs in 5 to 10 % of early pregnancies as well as a further 7% of pregnancies between day 70 of gestation and 24 hours post parturition.
Dr Jessica Lawson, Alborada Trust Research Fellow at the RVC, and Professor Mandi de Mestre at the Baker Institute for Animal Health at Cornell University led the research team embarked that studied the relationship between genomic inbreeding levels and pregnancy loss in thoroughbreds.
Their analysis of DNA samples from 189 individuals, including a control group revealed thoroughbred pregnancies lost in mid and late gestation (MLPL) had significantly higher inbreeding metrics than for UK thoroughbred adults. However, early pregnancy losses (EPLs) showed no discernible difference in inbreeding metrics compared to adult thoroughbreds.
Lawson emphasised the significance of the study's findings, emphasising the tangible impact of mating highly related individuals on breeding operations.
“The take home from our work should be to carefully consider breeding choices that involve mating of highly related individuals as, ultimately, this may increase the chance of the foal inheriting mutations which may not be compatible with life. We are already working on the next step, looking to identify these changes so more specific advice can be provided in the future,” she said.
By delving deeper into the underlying mechanisms of pregnancy loss, researchers aim to provide breeders with more targeted and effective guidance to optimise breeding practices and ensure the welfare of thoroughbred populations.
Funding for the research was provided by the Thoroughbred Breeders Association, Horserace Betting Levy Board, the Alborada Trust, and partial PhD studentship funding from the Royal Veterinary College's Paul Mellon Trust for Equine Research.
Pic: Jeff Griffith
