Updated September 2022.

Here at SPILLERS we are proud to have been researching senior horse nutrition for over twenty years. This journey began in the early 2000’s with work that investigated age related changes in taste and feeding behaviour in stabled horses. Since then, our research has extended into several areas including metabolism, nutrient digestibility, insulin response and gut microflora. With the health and welfare of senior horses being very close to our hearts, we wanted to share some of our key highlights with you…

Protein Requirements

Original research published in the 1980’s suggested that older horses may require more protein in their diet due a reduction in their ability to digest protein. However it was later questioned whether these findings could have been the result of previous worm damage rather than age. Later research (conducted in collaboration with SPILLERS) in healthy horses known to have received appropriate worming management found no difference in crude protein digestibility between adult and aged horses.

Nutrient digestibility

Have you ever wondered whether ageing affects your horse’s ability to digest nutrients? A recent study found that in healthy horses, ageing did not affect energy, protein, NDF (fibre) or mineral digestibility regardless of the type of diet fed (hay only, hay plus a starch & sugar based feed or hay plus a fibre & oil based feed). However, digestion of minerals from the hay only diet was significantly lower in all horses regardless of age, highlighting the importance of feeding a balancer even for horses that are retired or at rest.

Gut bacteria

The horse’s hindgut is home to complex microbial ‘community’. It’s well known that these microbes are essential for fibre digestion but in recent years, the influence of the ‘gut microbiome’ on health and disease has become an area of increased scientific interest both in human and veterinary medicine. Research published in 2014 found that whilst aging does not affect the structure of the bacterial community in healthy horses, it does reduce bacterial diversity. However this reduction in diversity was not seen when this research was repeated in ponies. Although the reasons for this are still unclear, these results may be related to longevity and suggest that ponies ‘age later’ than horses.

Insulin response

Insulin is a hormone secreted by the pancreas which signals cells, particularly those in the liver and muscle, to absorb glucose from the blood. Insulin dysregulation, a term which includes a hyperinsulinemia (a high level of insulin in the blood), an excessive insulin response and/ or insulin resistance has been associated with an increased risk of laminitis. Two studies which investigated the relationship between age, diet and insulin dysregulation found that ageing results in an increased insulin response to a starch rich or sugar rich meal even in healthy horses. These results suggest that restricting the amount of starch and sugar in the total diet may be beneficial in  all senior horses, even if they don’t have PPID (please contact the Care-Line for specific advice on feeding laminitic horses and ponies including those with PPID).

Diet & PPID diagnosis

Diagnosis of PPID or ‘Cushing’s syndrome’ involves a blood test which measures the level of adrenocorticotropic hormone or ‘ACTH’ in the blood. Diagnosis can be notoriously challenging because ACTH levels can be affected by several factors including the time of year and ageing itself. However recent research has shown that a high starch diet can also increase the concentration of ACTH in the blood which may lead to a false diagnosis of PPID.

Why do we publish scientific research?

We are still far from having all of the answers and the senior horse continues to be a key area of focus in our research programme. In order to support its credibility, research must be independently reviewed before publishing to ensure a suitable level of scientific rigor has been applied to all areas of the study, including interpretation of the results. By publishing our work we hope that we can help to improve the health and welfare of senior horses and ponies throughout the world.

For more advice on feeding your senior horse or pony contact the SPILLERS Care-Line.