Older horses, like older humans, cannot do so much and are more vulnerable to disease and mal-conditions due to the consequences of wear and tear over the years.
As they are less active their diet requirements can appear less as far as providing short feed is concerned, and that may be the case as there is not the need for calorific feeds to top up energy which is contributed by long fibre digestion as is so necessary in the younger more active horse.
However, lowering the extra calories may be only part of what is being contributed by the short feed, it may also be contributing some protein and to cut this out it may not be such a good idea …especially if the amount of protein coming from forage is marginal and the variety limited.
Quantity of protein in grammes per horse per day is straight forward; variety is more difficult to judge. Variety is important; this is because the protein in vegetable matter, with one outstanding exception, is incomplete protein.
Incomplete protein means that there is not the full number of essential amino acids. Vegetarian humans live and can thrive eating only incomplete protein because they consume a variety of different vegetables, seeds, and fruits which compensate for one deficiency with another. Horses do not usually have the luxury of such a variety of incomplete proteins, but they compensate by not having so many essential amino acids as they can feed off the products of fermentation from their ‘semi-ruminant’ digestive system and synthesise a greater number of amino acids …..as long as this arrangement is not upset by a drop in protein or sudden trauma.
A reduction in health and fitness can occur due to a straight forward insufficiency of the essential amino acids or, just as importantly, as essential amino acids are needed for their synthesis. A shortage of certain non- essential amino acids (not essential to be in the diet, that is, not necessarily less important). This why the essential amino acids, threonine, histidine, lysine, methionine etc are called ‘First Limiting’ because if they are short, no matter how good and plentiful the rest of the nutrients are, and how good the care and medication is, nothing will work properly.
A long miserable winter, on top of the poor quality forage and feeds due to the dreadful summer of 2012, has taken its toll and we are, even in early July, seeing many horses still not quite right due to marginal protein levels prevailing for too long.
The health and silkiness of haircoat (not necessarily the glossiness) is affected quickly by variation in protein levels and this is because much of the makeup of the mucus membranes is in the form of protein and with a high proportion of the non-essential amino acids including Cysteine and Glycine, it helps to have some present in the diet, but that which is not, has to be synthesised in the liver which means there must be sufficiency of essential amino acids and unimpaired liver function.
Viral challenge has a debilitating effect on liver function and in turn protein synthesis and the immune system. Any delay in returning to normality can result in post viral problems that include anything from tiredness, skin problems and in some horses sarcoid outbreaks… hence the popular advice for sarcoids to increase lysine levels.
Goldenmeal, Formula 4161, and Tenderfoot contribute complete proteins with the last two containing extra levels of non-essential amino acids for special collagen & skin tasks, and often such formulae as these become priority as they are the providers of the ‘ first limiting nutrients’.