A well-cared for cow may last through 10 or more lactations. Farmers may decide to cull a cow after two or three lactations because of a drop in production, problems breeding or health problems. Heifers must be fed before they calve and all through lactation. That's why some graziers are seasonal dairymen, milking only while they can feed their cows on pasture. They time their calving for spring grasses.
Farmers keep looking for a return on their inputs.
They have buildings, equipment, seed, feed, vet costs, animal costs, breeding costs and even wages and insurance. Increasing milk production is viewed by some as one way to increase returns. But there are risks. There are the hazards listed on the label and consumer reaction. Consumers demanded and received special labeling on dairy products so they would know which items were BGH-free.