Some horses appear to be hypersensitive to alfalfa. It remains unknown if this reaction can be attributed to the alfalfa itself, or to alfalfa contaminated with phototoxic substances such as pyrrolizidine alkaloids (PAs), which is also found in ragwort. This contaminated alfalfa can result in signs of mud fever or ‘sunburnt’ spots.
Instead of alfalfa you could use a different source of protein such as soybean (which does have a hormonal effect on the body), potato or pea protein, or linseed. Broken linseed contains good proteins, but you can’t use big doses on this because of the danger of hydrocyanic acid. To avoid this risk you should boil the linseed, but this changes the proteins in it.
You can instead feed varied roughage with several types of grass, but be aware that protein digestion from roughage takes place in the colon and appendix only if the intestinal flora is healthy.
Rye grasses often contain a lot of protein, but not the types of protein that a horse needs.
Our advice remains to add uncontaminated alfalfa is based on the practical availability and it also has a beneficial effect on the stomach. If more than 1 kg of alfalfa is added, it is important to keep an eye on the calcium / phosphorus balance.
Horses with a sensitive stomach tend to have problems eating alfalfa because it hurts in the stomach. Soaking the alfalfa could help, or try feeding the horse alfalfa pressed into pellets.