Joe,
Several vets and our local Extension Agent.
On the web: Lactase (the enzyme necessary to digest and process lactose) is encoded by a single genetic locus on chromosome 2.[12] It is expressed exclusively by mammalian small intestine enterocytes and in very low levels in the colon during...
Please be aware that chickens are lactose-intolerant and while probiotics are great for mammals, who are all weaned on milk they have no appreciable value for birds - who are not.