The race is on to breed better birds as chicken emerges as the protein of the masses ... Unlike the roughly 60 billion chickens world-wide now slaughtered for meat each year, these birds are raised for their DNA. Paul Siegel, professor emeritus of animal and poultry sciences, studies how their genes influence the way they pack on pounds and fight off disease. The research helps companies seeking to breed chickens that will grow faster on less feed and require fewer drugs to stay healthy. ... Food producers face a monumental task. At current consumption rates, the world would need to generate 455 million metric tons of meat annually by 2050, when the global population is expected to reach 9.7 billion, from 7.3 billion today. Given today’s agricultural productivity, growing the crops to feed all of that poultry, beef and other livestock would require every acre of the planet’s cropland, according to research firm FarmEcon LLC—leaving no room for raising the grains, fruits and vegetables that humans also need. ... Chicken’s rise already is changing time-honored habits. In Argentina, where grass-fed beef has long been central to daily life, per-capita poultry consumption is projected to climb 7.5% this year to a record level, while beef consumption is expected to decline 6.3%. Even in pork-loving China, the government has subsidized large-scale poultry farms and breeding operations over the past decade to increase output.