With no fanfare, Starbucks Coffee Co. this month began using milk products without a controversial artificial growth hormone in its home state. But the switch may drive up the cost of your caffeine habit. The company said Tuesday that it has stopped using dairy products with Recombinant Bovine Growth Hormone, or rBGH, in company-owned stores in Washington, Oregon, Idaho, Alaska, Montana, Northern California and New England. The supplement, approved by the federal government more than a decade ago, is given to dairy cows during the middle phase of lactation to produce more milk.