Researchers at the Massachusetts Institute of Technology (MIT) found male mice, which were fed the vanilla-flavoured dessert, had a certain 'swagger' when they walked.
They discovered these mice had testicles that were five per cent higher than other mice on a normal diet and 15 per cent heavier than junk-eating males.
What is more, in mating experiments the yoghurt-eating males inseminated their partners more quickly and produced more young than control mice.
Yoghurt-fed female mice benefited too -- they had larger litters and were more successful at weaning their pups, the Daily Mail reported.
The findings could have implications for human fertility and the team will next look at the association between yoghurt and semen quality in men, the researchers said.
The MIT team stumbled across the interesting finding when studying the effects of yoghurt on obesity. In a bid to prove whether yoghurt could help stave off age-related weight gain in humans, the researchers fed pro-biotic vanilla yogurt to mice with some unexpected results.
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It was found that the yoghurt-eating mice had shinier fur than their non-dairy fed siblings and the male mice were described as all of a sudden having a "swagger".
"We knew there was something different in the males, but we weren't sure what it was at first," said study author Susan Erdman. "You know when someone's at the top of their game, how they carry themselves differently? Well, imagine that in a mouse."
Other beneficial effects included slimmer bodies and shinier fur in both sexes as yoghurt-fed mice had 10 times the active follicle density of the control group.
Not only did the female mice sport the shiny fur coat and considerably slimmer physique of their male counterparts, they also tended to be better mothers to their larger litters.
"We think it's the probiotics in the yoghurt," said Eric Alm, co-author of the study. "We think those organisms are somehow directly interacting with the mice to produce these effects."