It has led to a phenomenal increase in milk production, from less than 10,000 pounds milk per cow per year average per herd to exceeding 20,000 pounds.
Bulls can smell when and which cow is in estrus.
People can only observe whether a cow is in estrus through change in her behavior. As a result, fewer than half of our dairy cows conceive when they should. More cows are culled from a herd for reproductive failure than for any other reason. The technical industry has tried many devices and procedures to make estrous detection by people easier and more successful. Yet even the farms on which ketch-up bulls are found have a conception rate no better than 1 in 2 cows bred.