Many horse owner's include lucerne either in the form of hay or chaff in their horse's everyday diets. The reason they feed it is usually because the horse likes it and it is what they have been taught is a good feedstuff for horses. It provides good roughage and bulk for their horse's and also smells nice and sweet. That is because it is sweet! It is loaded with sugars and great to help provide your horse with extra warmth and energy. Lucerne is also high in protein and calcium. It is useful to feed it at a competition where your horse is using a lot of energy and needs the extra usable fuel. Examples of this would be at endurance rides, polocrosse or any other high energy burning horse sport. It is also useful to help growing youngsters that need to put extra fuel into correct growth. Does this make lucerne a suitable every day feed?
Lucerne is primarily used to help fatten cattle for slaughter. Cattle eat around 1/3 of what horses do because they regurgitate and then redigest their food making it easy for their systems to process the high protein content. Horses on the other hand have only one stomach and only chew their food once and then their system is responsible for effectively processing the food. If there is extra protein and calcium in the diet without being balanced out by the correct phosphorus ratio it can cause all sorts of issues in the horse. The horse can develop the thumps, muscle cramps, tying up and kidney disease and also have many problems associated with their endocrine system not working correctly.
What is the short answer when it comes to how much lucerne to feed your horse?
Firstly, remember that it is used for cattle who are not meant to live or be performing for up to and beyond 20 years of age. Secondly, if your horse has seemingly behavioral issues, reduce or remove the lucerne from their diets in order to help their system level out and then add it in as necessary dependent on how much your horse is worked, what their discipline, what their growth needs are etc.