Senior horses are like any mammals—age is it’s not just a number! Feeding and managing horses well in their twilight years requires a balance of art and science. This article sheds light on a few of the studies that have helped to improve our knowledge of how best to care for senior horses.

Of course, there have been others and there will be more to come, so look out for more articles on ‘senior science’ in the future!

Marvels of the Microbiome

The horse’s hindgut is home to trillions of tiny microbes including bacteria, viruses, and fungi that are essential for fibre digestion and helping to regulate the immune system. Research in healthy horses found that ageing was associated with a reduction in the diversity of hindgut microbes, which might make some older horses more sensitive to changes in diet.

Interestingly, no reduction in diversity was seen when this research was repeated in similarly aged ponies. Although the reasons for this are not yet clear, these findings may suggest that ponies ‘age later’ than horses.

Tip: Remember to make all changes in feed and forage gradually wherever possible. As a guide, suggest replacing up to 500g of current ‘bucket feed’ for 500g of new feed every other day for horses, less for ponies. Ideally, changes in forage should be made over a minimum period of 3 weeks.

References: Dougal et al (2014), Morrison et al (2018)

Ageing and Nutrient Digestibility

If you’ve ever wondered if ageing affects the horse’s ability to digest nutrients, you are certainly not alone.

Research published in the 1980s suggested that older horses might require more protein in their diets due to a reduction in their ability to digest it. It was later questioned whether these findings could have been the result of previous worm damage rather than age.

A few decades later (2014), research found that in healthy horses, ‘being senior’ did not affect energy, protein, or NDF (fibre) digestibility. This was regardless of whether they were fed hay only, hay plus a starch- and sugar-based feed, or hay plus a fibre- and oil-based feed.

A followup study showed that age had no effect on mineral digestibility. In fact, mineral digestibility from hay was low in all horses, highlighting the importance of feeding a balancer to those that maintain weight easily on forage alone.

These and similar studies in ponies suggest that age per se doesn’t affect nutrient digestibility, at least for horses and ponies fed appropriate amounts of suitable forage. However, senior horses should still be fed plenty of good-quality protein to help support their muscles.

References: Elzinga et al (2014), Elzinga et al (2017), Morrison et al 2018

Tip: Feeding the recommended amount of a suitable feed or balancer will help to provide the vitamins, minerals, and quality protein needed to balance forage.

Obesity and Immune Health

Obesity carries a host of health and welfare risks for any horse, but it might have additional consequences for senior horses. One issue is exacerbating ‘inflamm-aging.’ This is a term used to describe chronic low-grade inflammation that occurs in association with aging.

In one study, a reduction in fat and bodyweight in senior horses resulted in reduced levels of inflammatory cytokine (molecules that promote inflammation) in the blood, while increased weight and fat had the opposite effect.

Reference: Adams et al (2008)

Tip: Balancers are ideal for senior horses that maintain weight easily on forage alone as they provide essential nutrients while adding minimal calories to the diet.

Diet and PPID Diagnosis

Diagnosing pituitary pars intermedia dysfunction (PPID) or ‘Cushing’s disease’ often involves measuring the concentration of adrenocorticotropin hormone (ACTH) in the blood.

Research published in 2018 found that a high starch diet might increase levels of ACTH in blood, potentially leading to the misdiagnosis of PPID.

Reference: Jacob et al (2019)

Starch and Sugar

While not all horses and ponies with PPID are insulin dysregulated, many of them are. That means they are at an increased risk of laminitis.

However, two studies found even healthy senior horses can have increased insulin response to a meal high in starch or sugar. This suggests that restricting starch and sugar intake might be beneficial for all senior horses, regardless of whether or not they have PPID or a history of laminitis.

References: Jacob et al (2017), Rapson et al (2018)

Tips:

  • Remember, restricting starch and sugar intake from ‘bucket feed’ is sensible for any horse as it helps to support digestive health.
  • Always seek advice from a nutritionist before changing your horse’s diet if they are prone to or have been diagnosed with diet-related clinical conditions such as laminitis, PPID, colic, gastric ulcers, or tying up.

Time to Retire?

In 2023, researchers published results of a survey completed by about 2,700 owners/carers of senior horses (15 years and over) in the U.S. Results shed light on the reasons why senior horses might be retired.

By developing a better understanding of when and why senior horses are being retired, it is hope that eventually we will be better placed to monitor for, prevent (where possible), and treat underlying conditions early on.

  • Most horses (62%) were retired between 15-24 years of age, with health problems given as the main reasons.
  • Horses with owner reported veterinary-diagnosed laminitis, lameness, and degenerative suspensory ligament desmitis had higher odds of retirement than those that did not have these conditions.
  • Around 1 in 6 horses had low muscle mass (muscle wastage), according to their owners. In most cases, owners felt this affected their horse’s welfare and ability to work.
  • Age, sex, osteoarthritis, laminitis, pituitary pars intermedia dysfunction (PPID), and primary use were identified as risk factors for low muscle mass.
  • Retired horses were at higher risk of low muscle mass than horses used for competition or pleasure riding.

Reference: Herbst et al (2023)

How Healthy is the Ageing Horse Population?

In follow-up to the retirement study, the same researchers published further data regarding the health and care status of senior horses in the U.S. Only 36% of owners/carers reported their horses/ponies to be free from veterinary-diagnosed illness. Osteoarthritis (30%), dental issues (15%), lameness (14%), and PPID (12%) were the most common health issues.

In this study, the risk of no health care visits, no dental visits, and being visited by the farrier less than 4 times per year times was found to be around 2 times higher in retired senior horses versus seniors used for pleasure riding.  

Reference: Herbst et al (2024)

Muscle Scoring

While many owners will tell you that their older horses have lost muscle tone, this observation might not be a direct effect of ageing. In fact, a reduction in exercise might have a greater effect on muscle tone than ageing per se.

While some degree of muscle wastage can occur with ageing, it can also be caused by lack of exercise, malnutrition, injury, poor saddle fit, some forms of tying-up, and certain other conditions. 

Muscle wastage can affect health and welfare in a number of ways, including a reduced ability to work or even simply the ability to get up after laying down.

In 2022, researchers published a system for scoring muscle atrophy or ‘wastage’ in horses in the neck, back, and hindquarters. Importantly, the system includes two scales that are based on the body condition of the horse. Did you know horses can have a high level of body fat but low muscle mass or vice versa!

Reference: Herbst et al (2022)

Tips:

  • Contact your vet if you notice your horse has lost muscle, especially if it seems sudden or severe. That might be a sign of injury or disease, particularly if there have been no changes in work or diet. It’s important to not assume muscle wastage is ‘just part of the ageing process’ as it might be due to something that can addressed or treated, such as saddle fit.
  • Check out this article on muscle scoring.

Scientific Resources

Further Reading

  • Sarah Nelson
    As Product Manager for SPILLERS, Sarah Nelson is responsible for the technical management of all SPILLERS products, including recipe formulation.
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