Obesity and insulin dysregulation, effects on mare reproduction and foal health

The effects of obesity and insulin dysregulation on mare reproduction, pregnancy, and foal health: a review

Front. Vet. Sci., 20 April 2023
Sec. Animal Reproduction – Theriogenology
Volume 10 – 2023 | https://doi.org/10.3389/fvets.2023.1180622

Isa Hallman1*, Ninja Karikoski2 and Maria Kareskoski1
1Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
2Department of Equine and Small Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
Conclusion
Maintaining optimal body condition remains critically important in broodmare management. According to this review, it is clear that obesity has the potential to create changes in both the reproductive function of the mare and the health and athletic outcome of the newborn foal. Since maternal obesity has been documented to cause structural and functional changes in the pancreas of the newborn foal and possibly predispose the neonate to osteochondral lesions later in life, the welfare aspect should not only be focused on the mare. Moderate overconditioning, or obesity without insulin dysregulation seem to be tolerable and even favorable to the mare from a fertility point of view. However, the magnitude and clinical relevance of the changes related to disturbances in insulin regulation described in this review are still uncertain. A noteworthy aspect is that while reproductive success does not seem to be greatly altered, insulin dysregulation may bring other clinical problems, such as laminitis, that are detrimental to the health and wellbeing of the mare.

Although measurable changes have been reported in several parameters related to reproduction, it is challenging to make definite, clinically reliable conclusions on a population level. Acquiring a large enough study population with long enough surveillance time is challenging in equine studies. Additionally, data is often published only on immediate changes and there are no long-term studies on large horse populations to fully elucidate the effect of high BCS or metabolic disturbances on the future generations. Obesity and insulin dysregulation/resistance are often grouped under one term, even though a clear distinction should be made between them, as obesity does not necessarily result in ID, and both can exist without the other. While the effect of obesity and elevated BCS have been studied rather widely regarding reproductive success, essentially only a minority of the studies have evaluated the insulin status of the horses. More studies are warranted to understand the role of ID on the reproductive processes of the mare and the health of future generations.

Obesity and insulin resistance will most likely continue to be a growing concern, as the horse populations in general have experienced a shift from working and athletic sport animals to hobby and leisure horses. One of the most important questions is the possibility of carrying the effects of obesity over generations and predisposing our future equine population to a cycle of disturbed energy metabolism.