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The sperm content can be less due to infection of testes;some sort of obstruction;varicocele
to name a few.To improve the content you need to get investigated to find the reason and then get treated for the cause.If there is no obstructive cause then you can start on antioxidant like Lycopene
and Co-enzyme Q 10 which are known to improve the sperm count
in absence of any disease or obstruction.For better opinion and treatment consult a Urologist
and he will do the needful.