How often do you hear it; in case of problems turn back to the basic. With sperm processing of stallions works that exactly , and the basic here is, of course, the stallion.
Is the stallion comfortable in his skin? Does he look good? Is he not too fat? The last two months had no fever? (often when there are many loose heads in the ejaculate, this may be an indication that the stallion has had a fever). Does he suffer from stress? How is he with collecting? Does he suffer from pain? There are many factors that can affect sperm quality, but always start at the base! The stallion himself.
A stallion is the most fertile in his younger years, on average 4-7 years. Up to 13-14 years of age, the sperm quality can be improve, but once a stallion is 15 years of age or older, the sperm quality can remain the same or becomes less. Especially in older stallions, adding vitamins and minerals often has a positive effect. Do not expect immediate results, it needs at least 6-8 weeks to see the effect.
Angus mc Kinnon has a fantastic quote, one that in my eyes can not be said often enough: “People believe that the stallion is just a sperm producing machine, they have little thought for the normal horse behaviour.” If the production and libido of the stallion is not high, only an custom management will work.
Good luck with the breeding season!!