Because we can always grab a quart of milk at the store, most of us don’t think of milk as seasonal. But cheesemakers do, especially if they work with goats or sheep. A dairy goat’s output dips and rises as the seasons change. Milk quality goes up and down. In summer, goats are generous but the milk is lean. In winter, supply plunges as farmers let pregnant goats go dry. For flavor and selection, spring is prime time. To experience the year’s finest fresh goat cheeses, leap now.