Something about putting chalk in dog food...
(,
Thu 8 May 2008, 23:31,
archived)
but i heard it's because vets are advising against giving dogs bones, so less calcium in the diet
(,
Thu 8 May 2008, 23:37,
archived)
And we were all wrong! Blimey...
snopes4.notlong.com
(,
Thu 8 May 2008, 23:50,
archived)
snopes4.notlong.com