Robots have taken up residence at some small- and medium-sized dairy farms across the country, providing reliable and more efficient labor and helping the businesses remain viable. Plus, farmers say, the milking technology makes for happier, more productive cows. Dairy operations here and abroad have used robotic milkers for more than a decade. But with more manufacturers and dealerships emerging the U.S., the number of smaller farms in Iowa with the technology has doubled over the last two years, from roughly 20 to more than 40, and family farms in the Northeast also are plugging in. The cost of not...