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Inbreeding leads to thoroughbred pregnancy loss, study finds
Inbreeding is commonly used in the breeding of livestock.

It contributed to mid and late-term pregnancy loss, but not early loss.

A new study has revealed that genomic inbreeding contributes to mid and late-term pregnancy loss (MLPL) in thoroughbred horses.

However the research, conducted by Royal Veterinary College (RVC), found that it had no contribution to early pregnancy loss (EPL).

The study saw researchers from RVC, in collaboration with Cornell University, analyse DNA samples from 189 horses, including a control group. The scientists studied the metrics of thoroughbred pregnancies that were lost in early, mid and late gestation.

Findings revealed thoroughbred pregnancies that were lost in mid and late gestation had significantly higher inbreeding metrics than in UK thoroughbred adults. In contrast, pregnancies which were lost early in gestation had no significant difference in inbreeding metrics to thoroughbred adults.

Inbreeding is commonly used in the breeding of livestock, to ensure that newborns carry desirable traits.

However, excessive inbreeding can increase the likelihood of uncovering homozygous recessive genotypes, which can be associated with a higher risk of retained placenta and lower semen quality in horses.

Five to 10 per cent of equine pregnancies result in pregnancy loss in the early stage of gestation. A further seven per cent are lost between Day 70 of gestation and 24 hours post parturition.

The findings of this study, which is the first to explore the effects of genomic inbreeding levels on late term pregnancy loss in horses. The researchers say that this highlights the importance of informed equine mating decisions to minimise the risk of miscarriages in thoroughbreds.

Dr Jessica Lawson, Alborada Trust Research Fellow at the RVC, said: “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.”

The full study can be found in the Equine Veterinary Journal.

Image © Shutterstock

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Practices urged to audit neutering data

News Story 1
 RCVS Knowledge has called on vet practices to audit their post-operative neutering outcomes.

It follows the release of the 2024 NASAN benchmarking report, which collates data from neutering procedures performed on dogs, cats and rabbits.

The benchmarking report enables practices in the UK and Ireland to compare their post-operative outcomes to the national average. This includes the rate of patients lost to follow-up, which in 2024 increased to 23 per cent.

Anyone from the practice can submit the data using a free template. The deadline for next report is February 2026.

Visit the RCVS Knowledge website to complete an audit. 

Click here for more...
News Shorts
UK's BSE risk status downgraded

The WOAH has downgraded the UK's international risk status for BSE to 'negligible'.

Defra says that the UK's improved risk status recognises the reputation for having the highest standards for biosecurity. It adds that it demonstrates decades of rigorous animal control.

Outbreaks of Bovine Spongiform Encephalopathy, also known as mad cow disease, have previously resulted in bans on Britain's beef exports.

The UK's new status could lead to expanded trade and better confidence in British beef.

Christine Middlemiss, the UK's chief veterinary officer, said: "WOAH's recognition of the UK as negligible risk for BSE is a significant milestone and is a testament to the UK's strong biosecurity measures and the hard work and vigilance of farmers and livestock keepers across the country who have all played their part in managing the spread of this disease.