09/12/2020
https://www.facebook.com/plantsforhorses/posts/1755603727938405
Please don't over rug this winter, your 'Good Doer' will thrive on surviving.
A ‘good doer’ is a pony or horse that can survive on fresh air, he is a survival expert, but with our modern management are we providing our good doers with a healthy environment or are we predisposing them to metabolic dysfunction? Good doers possess alternative energy systems to help them survive in harsh environments, every now and again they need a harsh environment to re-establish or balance energy metabolism.
What is a harsh environment? We may not like to see horses in a field, without a rug, with a hairy coat, very little grass and only low grade hay/straw to eat, but is this better for the native pony good doer than to have a life time of EMS leading to laminitis?
‘Cresty’ necks are unsightly lumps of fat found on the neck of an overweight or obese horse and there is a growing awareness amongst vets and horse owners that having a ‘cresty neck’ predisposes it to laminitis.
Some breeds are more prone to having a ‘cresty’ neck than others, native breeds such as the Welsh, Connemaras, Highlands and Shetland ponies are among the more susceptible as they require less food with lower sugar/starch than many of the other breeds, they also have a natural leaning towards insulin resistance because they have evolved from an environment where food supplies are often scarce and available nutrients change from season to season. Susceptible ponies (and cross breeds) are called ‘good doers’ and they possess an insulin resistant genotype as a survival mechanism which makes them more likely to develop insulin resistance, a good thing as it helps them to survive their native harsh mountain/moorland environment. These ponies naturally have a higher level of insulin secretion and a slower glucose disposal rate which is a positive adaptation for sparse food rations.
During the harsh winter conditions when glucose is unavailable or scarce the ‘good doer’ will switch to an alternative energy system to ensure survival and as the available food changes from grass to shrubs/herbage such as gorse, tree bark and marsh grass the metabolism will also switch to a more conservative system of energy use and storage which prevents any ingested glucose from entering the muscle and adipose tissue. Deprived of glucose the tissues then start to use another energy supply (lipids/triglycerides) allowing the dwindling but precious sources of glucose to support vital organs. ‘Good doers’ have lower insulin sensitivity and higher insulin secretion plus high circulating levels of triglycerides. This tendency towards insulin resistance is a natural efficient adaptation which also involves the ‘pay it forward’ insulin system which exists in the gut.
The problems start when the ‘good doer’ clashes with the modern management system and change of environment, and switches to a diet containing too much sugar and starch from hard feed, high quality hay and grass (perennial rye) designed by modern farming methods as suitable for high milk yielding cattle, with no drop in the quality of nutrients through the winter months. ‘Good doers’ are more predisposed to laminitis but any horse receiving more calories than required for work will store the excess as adipose tissue and fat pads will soon appear as ‘cresty necks’, tail pads, shoulders, sheath etc and has the potential to develop endocrinopathic laminitis.