I absolutely do not believe this. There isn't a single writing by a biologist or scientist to support doe making estrous bleats while in heat and that statement was made by a biologist but I cannot remember which one. More so than anything it's nothing more than a contact call. Although this site offers two different calls, they are very similiar and the "Can" sounds more like the contact called made season long.

http://www.bowsite.com/bowsite/features/practical_bowhunter/deergrunting/deergrunt.html