Attention to detail results in healthier flocks and fewer losses.     Chickens bred to grow in climate-controlled barns often perform poorly in an outdoor environment. Gowing facilities should be considered during breed selection.                                                 The Camrose Canadian   Chickens bred to grow the fastest in climate-controlled barns aren't necessarily the best birds to raise in a pasture, a hatchery owner says. Cornish Giants, the large white broiler birds that have been bred to grow quickly and efficiently in modern chicken barns, need ideal conditions to grow. "If you're going to use them for pasture poultry, you must understand its weaknesses. If you're going to throw it our there and not look after it, you're going to have a disaster," said Al Keshwani, owner of Rochester Hatcheries in Rochester, Alta. These birds tend to have leg and heart problems. They have a large appetite that compensates for poor quality feed.       A better choice of bird for pasture is the Cornish cross, he said. While it takes two weeks longer to finish, it seems to do better on grass. "It's not the most efficient bird, but if conditions aren't ideal the losses won't be as great," said Keshwani, who has heard of 50 percent death losses with the Cornish Giant broiler. Unlike the Cornish Giant, the Cornish cross doesn't do well on poor quality feed. Without good quality feed, it will grow even slower.