A genetic challenge:
In 1942, when my father was born, the average dairy cow produced less than 5,000 pounds of milk in its lifetime. Now, the average cow produces over 21,000 pounds of milk. At the same time, the number of dairy cows has decreased from a high of 25 million around the end of World War II to fewer than nine million today. This is an indisputable environmental win as fewer cows create less methane, a potent greenhouse gas, and require less land.
At the same time, it turns out that cow genomes are more complex than we thought: as milk production amps up, fertility drops. There's an art to balancing all the traits that go into optimizing a herd.