It has become a common practice to feed non-saleable milk to dairy calves. Non-saleable milk accounts for 1–4% of the total milk produced in the farm and this includes milk from antibiotic-treated cows along with colostrum from fresh cows and milk containing high somatic-cell-counts.
Milk production is often wrongly considered to be a major source of the greenhouse gases (mainly methane) affecting climate change. Researchers from Switzerland evaluated whether increasing the productive life of cows reduces greenhouse gas emissions as it reduces emissions from the rearing of replacement heifers.
Over the past decades, the Holstein breed has undergone the process of extreme selection which emphasized production and conformation rather than fertility and health. This, along with an increasing average inbreeding of Holstein cows, has promoted the use of crossbreeding in U.S. dairy farms.