I personally don't think so, unless in life-threatening situations.

The dairy industry is arguably the worst of factory farming: all the horrific aspects of the meat industry, but prepended with years of subjugation (forced insemination, illness, etc.)

In the best case, a cow is treated like a pet, which A.) is never the case, and B.) still necessitates taking something from an animal without it's consent. Something that is specifically for it's newborn, as well. That's _always_ gonna be wrong, unless it's a matter of life and death for someone.