Bread-Bakers v103.n013.4

Whey is recommended for breads, cakes, biscuits, etc to supply the acid 
needed to react with the alkaline baking powder or baking soda and 
facilitate rising.

I doubt if it would have any beneficial effect on yeast-raised doughs. 
Maybe the acidity might even retard the growth of yeast.  I can't see any 
point in using it in bread dough.

Best wishes,

Max Prola
Cheshire, England