The Equine Limbic System

In this episode Nancy McLean answers a listener’s question about choosing off-the-track Thoroughbreds (OTTBs) for eventing and reviews recent research on how past racing careers influence post-racing eventing levels. She summarizes Bacon et al. (2025), which found that shorter racing careers and longer race distances are associated with greater likelihood of reaching higher eventing levels, while long track longevity and involuntary retirements (injury/health) reduce that likelihood. Nancy also highlights factors like pedigree, early-life influences, and the importance of the rider–horse relationship. The episode offers practical tips — check racing records (Equibase), prioritize personality and a patient retraining timeline, and consider evidence-based retraining programs such as Kate Fenner’s  Race2Ride. Bacon, E. K., Parnell, D., Muscatello, G., McElroy, J., & Velie, B. D. (2025). How prior racing performance influences competition level in off-the-track Thoroughbred horses' post-racing eventing careers. Journal of equine veterinary science, 154, 105679. https://doi.org/10.1016/j.jevs.2025.105679 Race2Ride link: https://www.race-2-ride.com/a/2148257211/YJ65wKcd  

In this episode Nancy McLean reviews a Tnibar (2025) literature review with seven equine studies showing 2.5% polyacrylamide hydrogel (IPAAG) provides long‑lasting, biocompatible intra‑articular relief for osteoarthritis, often reducing or resolving lameness from one month up to 24 months in many horses. The episode summarizes study outcomes, notes rapid onset in some horses (as early as one week), typical post‑injection management (about one week stall rest with hand‑walking), and highlights effects on joint capsule elasticity and viscous supplementation that may protect articular surfaces. Nancy contrasts 2.5% IPAAG with 4% products, explaining that 4% differs in manufacturing, contains silver ions, and currently has less published evidence and unclear safety compared with 2.5% IPAAG.

This episode reviews cases of steroid-induced laminitis and examines recent research and owner-reported experiences using SGLT2 inhibitors (most commonly ertugliflozin) as an off-label treatment for equine metabolic syndrome and hyperinsulinemia-associated laminitis. An online survey of 342 owners found most horses treated with SGLT2Is showed improved quality of life and reduced pain, with many horses spared from euthanasia; common initial side effects included increased drinking and urination, weight loss, and dullness, which were often dose-dependent or resolved over time. Key takeaways: SGLT2Is show promise as a rescue option for laminitis when combined with strict dietary management and good hoof care, but long-term safety, availability, cost, and further research remain important considerations. Research  https://beva.onlinelibrary.wiley.com/doi/abs/10.1111/eve.14071 https://scholar.google.com/scholar?hl=en&as_sdt=0%2C14&as_vis=1&q=sundra+et+al+2025+Horseowner&btnG=#d=gs_qabs&t=1787417730062&u=%23p%3DSFYkeG9TZt4J Humble Hoof Podcast Episode https://open.spotify.com/episode/4CvEegebGNduL7hNJDAlFc?si=UWRrM3TuRJuXyg0Rxx_vSA&utm_source=copy-link  

Updates on preliminary research findings on steroid use and insulin deregulation in horses.

This episode explores whether horses can experience headaches by examining cervical spine pain, common signs like head rubbing or altered carriage, and how musculoskeletal and nervous system issues contribute to discomfort. Nancy reviews diagnostic options, treatment and rehabilitation strategies, and the need for improved imaging and physiotherapy to restore performance and well-being. Research Link: https://www.mdpi.com/2076-2615/11/2/422  

In this episode Nancy McLean answers listener emails about geldings that chew lead ropes and reins, she explains how cortisol and the HPA axis relate to stress-driven behaviors, and describes how consistent training, handler calmness, routines, turnout, and nutrition can help horses down-regulate stress. The episode also summarizes research on cortisol sampling methods (plasma, saliva, hair) for short- and long-term stress assessment, and closes with a brief update on a new world screwworm outbreak, what has been done historically to eradicate it, and practical steps owners should take if they suspect infestation. Research: https://www.mdpi.com/2077-0472/13/12/2219 https://assets.cureus.com/uploads/review_article/pdf/413141/20251106-69309-xadaoe.pdf  

In this episode Nancy McLean explores a listener question about whether to remount after a fall, using Dr. Stephen Peters’ research and a review by McBride et al. to explain how equine learning, myelination, and long-term potentiation shape behavior. Nancy explains how automaticity, basal ganglia consolidation, and dopamine-driven rewards can help overwrite fearful responses, and she shares a real-life example of calmly remounting to reinforce positive patterns. Key takeaway: when horse and rider are uninjured, a calm remount and rewarded repetition can help redirect the horse’s neural pathways and prevent lasting fear responses.

The core of the equine brain’s emotional center, Nancy describes how the neurological processes of the limbic system take place. She also highlights the reward prediction error (RPE) and the impact it has on equine learning.

This is a continuation of our study on Equine Neurology and Ethical Horse Training and Management.

In this episode Nancy McLean explores Dr. Stephen Peters' book Horse Brain Science, comparing human and equine brain anatomy and function. She explains brain size and cortical folding, then walks through the four main lobes (frontal, parietal, temporal, occipital), the amygdala and hippocampus, and the brainstem. The episode connects these brain differences to horse behavior and training—why punishment fails, how pressure and removal or positive rewards work, and how understanding sensory processing, memory, and fear responses can improve ethical horsemanship.