Senior equid research has moved in leaps and bounds in our lifetimes. What is the most important to us and our senior horses, ponies, donkeys, and mules? In this episode of the My Senior Horse podcast, we speak with Pat Harris, MA, PhD, VetMB, DipECVCN, MRCVS, EBVS. She is a past president of the British Equine Veterinary Association and is a European specialist in veterinary and comparative nutrition. She is the Director of Science for Mars Horsecare and Head of the WALTHAM™ Equine Studies Group. 

Harris has spent much of the last 30 years working to help improve the care and nutrition of older horses. She also is passionate about seniors because of her dedication to her own older horses. She also has advised on the care of many other seniors and has authored many articles on their care. Harris’ involvement in several  global senior research teams gives her special insight into some of these studies.

Harris  is also on the Executive Advisory Council for My Senior Horse.

Senior Research Advances

The advances in the knowledge and application of nutrition in equine health has been the top research advancement, said Harris. Research advances range from the use of vegetable oils and highly digestible fibers to how much sugar and starch we should feed.

“My number two top research advancement is our better understanding of—as well as the early detection and management of—the key metabolic diseases in senior horses,” said Harris. “And for me this includes obesity, laminitis, and of course PPID/equine Cushings.”

Harris went on to discuss insulin’s relationship to equine laminitis. “I think we often forget that it’s actually only relatively recently that we’ve understood the importance of insulin in many laminitis cases,” she noted. “This has opened up a whole new area of research, not only with respect to nutritional management, but also risk prediction and importantly veterinary management.”

Her third area of research importance was the all-around improvements in veterinary diagnosis, diagnostics, and treatment for older horses. This especially covers several key conditions that affect senior horses, including arthritis and GI issues such as ulcers.

Survey on Senior Health

“I think the importance of these three areas was actually highlighted to me and to all of us in the results of a survey that was done of nearly 3,000 owners of senior horses,” said Harris. She said the survey took in U.S. horses aged 15 and older. The survey was done by Dr. Alisa Herbst and Dr. Amanda Adams at the University of Kentucky in collaboration with Waltham..

Results from the first parts of this survey have just been released in 2024.

“This study showed that most horses were retired from work or retired completely between 15 to 24 years of age,” Harris noted. “And most of them were retired with health problems being cited as the main reason for their retirement.”

The survey showed that only about one-third of the horses were said to be free of signs of declined health.

The most common veterinary diagnosed condition in this survey of owners was osteoarthritis. The second-most-common condition reported was dental disorders. Other top ones included PPID and laminitis.
“So, I think that survey really highlights the importance of the three areas that I mentioned,” Harris said.

MySeniorHorse.com helps bring these research findings out of the veterinary journals and to horse owners globally.

Senior Research Topics

“I’m really fortunate and privileged to have been able to collaborate with colleagues around the world on the various aspects of feeding and managing the older horse with or without insulin dysregulation and with or without PPID,” said Harris.

She said that and other studies have enabled researchers to “explore aspects that will pick up going forward into digestibility, the microbiome, insulin dynamics, and transport stress.”

Research she has participated in includes looking at older horse protein requirements. She said there was a theory that senior horses had a reduced ability to digest protein.

She collaborated with colleagues at the University of Michigan digestibility of nutrients, including protein, in the equine diet. “We compared a group of healthy older horses with a known history of practices and compared them with younger horses,” said Harris.

They found no difference in protein or energy digestion in senior horses fed sufficient amounts of quality forage.

“So even though we didn’t find a difference in this study, we know from others that protein is really important to consider in our older animals,” said Harris. “Protein quality remains key. We’ve shown that the actual requirements of the protein—specifically key amino acids—will depend on the individual and the workload.”

Senior Horse Microbiome and Nutrition Requirement Research

Harris has been a collaborator on a number of  studies with the University of Liverpool, Michigan, Mississippi State, and Aberystwyth to look at digestibility and fecal bacteria (the microbiome). She goes on to mention some of the findings.

“We found a reduction in the diversity of the microbiome in older horses, but not older ponies of similar age,” Harris said. “This might possibly be linked with postulated differences in longevity between some horses and ponies.”

PPID-positive horses were associated with decreased circulating vitamin B12 concentrations in one study. That research was conducted by the University of Kentucky in collaboration with Harris.

“We showed that even though these animals were being fed recommended NRC levels of vitamins, giving additional vitamin supplementation to older animals may help improve vitamin status.” she said. “Over supplementation is not necessarily, but making sure we don’t forget to provide adequate amounts is so important.”

Final Words

To hear more of what Harris talked about in this podcast, make sure to tune in to this episode. Those topics included:

  • effect of feeding fiber, starch, and oil rich diets on the insulin response (What it showed is that the older animals tended to have a more pronounced insulin response to the high sugar and starch diet. That has led to the current recommended suggested levels for older horses even those without Insulin dysregulation.);
  • laminitis and obesity;
  • why some of the more dominant horses are more obese than others in the herd;
  • how to best use grazing muzzles;
  • body condition score; and
  • predicting laminitis.

Further Reading

Check out these articles authored by Harris on MySeniorHorse.com:

  • Kimberly S. Brown
    Kimberly S. Brown is an award-winning writer and publisher. She is the Editorial Director for My Senior Horse. Brown spent 10 years at Equine Network, parent company of My Senior Horse. Prior to that she worked for three years in equine nutrition after she retired from nearly 30 years working at The Blood-Horse. Brown spent the last 15 years of her time at that organization creating and developing The Horse and TheHorse.com.
    View all posts