Merck ($MRK) reported that sales in its animal health unit fell 6% year over year to $830 million in the fourth quarter of 2015, which included a 14% negative impact from foreign exchange rates. The full-year picture wasn't much brighter: Revenues fell 4% to $3 billion. But Merck's animal health unit is still expanding, with demand for its products to treat companion animals on the rise, as well as continued growth in its aquaculture and swine lines. Minus the impact of currency woes, 2015 sales of animal health products were actually up 9%, thanks largely to strong demand for Bravecto, the company's chewable pill to combat fleas and ticks in dogs, Merck said. Release