When I just hit up Google with "probiotics testicle growth", one of the hits is an article about a study suggesting yogurt leads to larger testicles in mice. But while the article is pushing probiotics the evidence pointed more towards the mice having a better overall diet with high protein, which was lacking in the control group.
http://bignaturaltesticles.com/low-sperm-foods-boost-semen-production/
http://bignaturaltesticles.com/low-sperm-foods-boost-semen-production/