Soy isoflavones are structurally similar to mammalian estrogens and therefore may act as estrogen agonists or antagonists. However, it has not been determined if they have any negative effects on reproductive parameters in male livestock. Therefore, the objective of this study was to evaluate the effects of soybean isoflavones on male reproduction using Chinese mini-pig boars as a model. Fifty Xiang boars were randomly divided into five groups and fed diets containing 0, 125, 250, or 500 ppm soybean isoflavones or 0.5 ppm diethylstilbestrol for 60 days.

The results of including high levels of soy isoflavones is the adult pig diets produced several metabolic responses, however, consuming soy isoflavones at dietary levels up to 250 ppm did not adversely affect reproductive parameters in Chinese mini-pig boars whereas higher levels of soy isoflavones may adversely affect male reproduction. Editor’s Note: The level of isoflavones in SBM is highly variable depending on soybean variety, the growing season environment and other unknown factors. However, it is known at the level of isoflavones in swine diets is insignificant and not a factor in determining performance.