A study of horses – which share many important similarities with humans in their chromosomes and pregnancies – revealed that 42% of miscarriages and spontaneous abortions in the first two months of pregnancy were due to complications from an extra set of chromosomes, a condition called triploidy.

“Over that embryonic period [up to eight weeks from conception], triploidy had rarely been reported in mammals outside of women,” said Mandi de Mestre, the Dorothy Havemeyer McConville Professor of Equine Medicine at Baker Institute for Animal Health and in the Department of Biomedical Sciences at the College of Veterinary Medicine. “The study tells us that over the first six weeks of gestation, this will likely be the primary cause of pregnancy loss following natural conception.”

De Mestre is the corresponding author of Naturally Occurring Horse Model of Miscarriage Reveals Temporal Relationship Between Chromosomal Aberration Type and Point of Lethality published August 5, 2024 in the Proceedings of the National Academy of Sciences.

Human miscarriages occur in 10-20% of pregnancies and are commonly associated with chromosomal errors, but there have been no suitable animal models that truly duplicate the features of the condition. The new research findings will help veterinarians better understand the causes of pregnancy loss in horses, and identifies horses as an excellent model for studying human miscarriage.

“We were able to study the impact of chromosome errors across the entire pregnancy in the horse,” de Mestre said. “We found that triploidy is only associated with losses in early pregnancy.”

In the study, de Mestre’s laboratory at Cornell, and earlier at The Royal Veterinary College, London, received 256 fetus and placenta samples from veterinarians who treated horses with failed pregnancies over a period of 10 years. Using the samples, the researchers were able to investigate the prevalence of different types of chromosomal copy number errors associated with pregnancy loss.

They found that chromosomal errors occurred in 57.9% of pregnancy losses up to day 55 of gestation, in 57.2% of losses between days 56 and 110 and in only 1.4% of losses between days 111 and the end of pregnancy.

Aneuploidy (loss or gain of a single whole chromosome) was mainly associated with miscarriages in the first 10 weeks of pregnancy, while deletions or duplications of only part of a chromosome were found in miscarriages after 110 days. These findings turned out to be remarkably similar to those observed in a number of large studies in women, according to the paper.

Horses are a good model for studying human pregnancies because they have a similar gestation period – 11 months compared to nine months in women – and the embryo develops at a similar rate in the early stages. In addition, horse chromosomes have a very similar genetic content to human chromosomes, which makes them particularly relevant for the study of chromosome errors.

Reasons for miscarriage in women in very early pregnancy have been difficult to determine because most fetuses during this period are lost at home, leaving scientists without material – and data – to study. The study’s findings provide insight into the frequency of chromosome errors over the equivalent period of the first six weeks of human gestation.

Because of the value of horses and the emotional attachment their owners have to them, horses receive a high level of care, with routine tracking of pregnancies, which then provide extensive data for research.

Other animal models, such as mice, are not comparable to human pregnancies. Mice have a gestation period of about three weeks, and natural pregnancy losses in mice are low.

In terms of equine health, the study provides new details about common chromosomal abnormalities that will likely change the clinical management of pregnancies.

For example, if a clinician determines that a horse has a major chromosomal error, they may no longer choose to extend that pregnancy by administering hormones, a common practice in pregnant mares. The study will also point researchers toward the development of new diagnostic tests for chromosome abnormalities in horse fetuses and investigating molecular mechanisms that lead to these abnormalities.

“This research has provided a foundation for understanding the genetic causes of pregnancy loss in horses, often referred to as pregnancy loss of unknown cause,” said Shebl Salem, a postdoctoral researcher in de Mestre’s Equine Pregnancy Lab and a co-first author of the study.

Other co-first authors include Jessica Lawson of the Royal Veterinary College in London, United Kingdom; and Donald Miller, de Mestre lab manager.

The study was partly funded by the Horserace Betting Levy Board and Thoroughbred Breeders Association.

This article originally appeared on the Cornell University "Cornell Chronicle" and is published here with permission.

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A horse can be a great companion. The nature of the association may stem from companionship, riding pleasure, or competing in contests. Assuring the health of your horse requires a dedicated journey of care and attention to detail. This includes giving them the right diet, getting regular check-ups and ensuring they have a suitable living environment and regular exercise schedule. Here is an ultimate guide for keeping your horse healthy.

1. Well-Balanced Diet

A well-balanced diet is key to health, regardless of your horse’s age, breed, and activity level. Having experienced different life stages during their lifetime, and some working harder physically than others, horses are subjected to various requirements.

• Young and growing horses need diets rich in protein and calcium for correct development.
• Older horses may need easily digestible feeds with supplements added to the diet to help maintain health.
• Performance horses need higher energy intake than those used for leisure.

Essential nutrients would include carbohydrates for energy, proteins for the development of muscles, and fats for supplying energy and maintaining good coat condition, with the addition of vitamins and minerals to maintain general health.

Supplementary feeds like salt blocks can complement the required electrolytes. Feeding schedules should stay as close as possible to a horse’s natural grazing habits by providing forage continually throughout the day while sectioning out grains and concentrates to avoid digestive complications and obesity. In some cases, a horse energy supplement may be beneficial for maintaining stamina during training or competition.

2. Hydration

Adequate water intake is essential for overall health, digestion, thermoregulation, and cellular functions in your horse. Access to fresh, clean water should always be available for horses. Horses consume five to 15 gallons of water within a 24-hour period, though this may increase in hot weather or after long rides.

Some signs of dehydration to look for in a horse include reduced skin elasticity, dry mucous membranes, and sunken eyes. It is also crucial not to over-hydrate, since this may cause an electrolyte imbalance. Keep replenishing your water source; heating may be recommendable during the cold months.

3. Veterinary Care and Routine Check-Ups

Regular check-ups allow problems to be identified at the initial stage and solved before it’s too late. Common problems among equines include colic, lameness, or breathing difficulties, which can be sorted out with a regular check by a veterinarian.

Preventative care is the key to good health. Vaccinations will prevent influenza, tetanus, and West Nile virus. Make sure to practice good dental care with regular check-ups and floating (filing teeth) to prevent dental problems that impact feeding and nutrition. Also schedule deworming to give no room for internal parasites to manifest.

4. Exercise and Physical Fitness

A well-rounded exercise program will be important to your horse’s physical and mental health. An appropriate amount of exercise means one that agrees with the size, breed, or age of your horse and their present level of fitness.

Regular sessions help maintain muscle and cardiovascular fitness and joint flexibility, adding to overall fitness. Other exercise benefits for horses include maintaining a healthy weight, improving digestion, and enhancing immune function. Additionally, regular activity strengthens the bond between horse and owner, fostering trust and cooperation. Whether riding, lunging, or turning out in a paddock, consistent physical activity leads to a fit and happy horse.

5. Proper Grooming and Hygiene

Daily grooming practices are necessary for a clean and healthy horse. Good grooming can eliminate dirt, debris, materials, and loose hair. Ensure that you inspect your horse daily for any injuries or skin conditions. Brushing, combing, and hoof picking complement each other as essential tools for grooming. Regular sessions also help bind you to your horse more effectively.

Attention should also be given to a clean and safe living environment. Stables should be dry, spacious, and free of hazards. To stop hazardous bacteria and parasites from growing, clean stables and equipment on a regular basis. A clean atmosphere improves your horse’s overall health by lowering the possibility of respiratory problems or other health problems.

6. Mental and Emotional Welfare

Horses are social animals that want to interact and stimulate their interests. For mental and emotional needs, ensure that your horse has some aspect of social interaction with other horses. Some enrichment activities include providing toys and creating stimulating environments to keep your horse engaged and mentally active.

It’s important to be able to recognize the signs of stress or behavioral problems. Any change in behavior or appetite could indicate that something is wrong. A calm and content horse can be maintained through consistent positive reinforcement, or with the help of an equine behaviorist.

Endnote

Following the best practices mentioned above is the best way to ensure your horse leads a healthy life. Consider what it eats and drinks, along with providing it with regular exercise and maintaining good hygiene. You also need to also prioritize veterinary services to keep their health in check.

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