Milk, however, comes from more than just cows. Cattle account for 81% of global milk production, followed by buffaloes at 15%, while goats, sheep and other dairy animals make up the remainder. With cattle responsible for the vast majority of the world's milk, this story narrows its focus to the dairy cow.

In an individual survey conducted by the author, 60% of respondents admit to drink cow's milk daily, describing it as a staple of their diet.

Yet when asked how cows produce milk, many were unfamiliar with the biological process behind it. That gap between consumption and understanding raises a less familiar question: what has to happen for that glass of milk to reach our table?

The next section will trace that process over the course of a cow's reproductive and productive life.

A Typical Life of a Dairy Cattle

Lactation As a Form of Maternal Care

Mammals are the only animals that produce milk from their mammary glands in response to produce sustenance and maternal care for their offspring. Until the young is able to chew and digest real food, they will usually strictly only consume this maternal production as a sole nutrition.

Calves are known as natural milk drinkers. Without any human intervention, they're known as vigorous feeders, often drinking large quantities in a single session.

In cows specifically, the first milk (colostrum), contains specific components which will support her calf's transition from intrauterine to parenteral nutrition. The special task of colostrum is the passive immunization of the newborn via its greater content of antibodies to bridge the first weeks of life until the offspring can produce its own antibodies¹.

In the dairy industry however, colostrum immediately harvested from the mother since its quality declines by approximately 4% for every hour collection is delayed.

What We Don't See Behind the Milk

By the time food reaches our plates, much of the work and life behind it has disappeared. A carton of milk arrives to us cold and sealed, far removed from the animal that produced it.

In reality, milk production is tied to reproduction. A dairy cow only begin to produce milk after giving birth, so pregnancy and calving are part of the cycle behind our dairy milk on store shelves. But their life cycle can be short. Although cattle can live for around 20 years, dairy cows in high-producing or industrial systems have an average productive lifespan of only about three to four years after their first calving. Including the time before their first calving, many died at around four and a half to six years of age.

We continue asking the respondents: do they know that dairy cows are kept pregnant for much of their lives to maintain milk production?

We then raised another question to the respondents: What usually happens to a calf shortly after birth?

On many commercial dairy farms, it is a routine practice to separate the calf from their mom within 24 hour of calving². The reasons are both economic and for human control. Early separation is often done to increase the amount of milk available for sale as calf is known to drink mother’s milk heavily. Another reason is to prevent a maternal bond from forming and making it harder to separate them later. Post separation, cows have been reported to show sign of distress: they will vocalize, calls become higher in pitch, and they stick their heads outside pens more frequently.

Cows are monotocous, meaning they usually carry only one child per pregnancy.

There are more and more people are concerned about the animal welfare side of this practice nowadays. Aside from early separation, there are many common practices that are being called out as 'cruel' in the dairy farming world. The first and foremost: the killing of male calves.

Disposal of Male Calves

When a male calf is born in a dairy farm, it is seen as economically unviable and inefficient. Their meat is often low of fat content and they do not contribute to milk production. More often than not, the decision is that they are immediately killed as baby calves. By killing them early, or often referred to as culling, owner of dairy farms won’t have to pay for housing, feed, or veterinary care.

Cited from Australian Veterinary Journal, in the state of Victoria only, about 600,000 male calves that are less than a week old were culled each year³.

Tail Docking

Tail docking means removing part of a cow's tail, usually done by rubber banding, hot blade, and rarely by surgical incision. This is still a common practice on dairy farms in many areas in the USA (even if it is prohibited in some states) and Australia.

With dairy cattle, it has historically been practiced because farmers believed it could improve hygiene, reduce the risk of manure contamination of the udder, and make milking more hygienic. The original rationale was that a long tail can become contaminated with manure. During milking, the tail may brush against the cow, the milker, or milking equipment. Many farmers therefore thought that shortening the tail would improve cleanliness and reduce the risk of contamination.

However, the scientific and veterinary consensus today is generally that routine tail docking does not provide those benefits sufficiently to justify the welfare costs. Many animal-welfare organizations and veterinary bodies oppose this procedure since it can cause acute pain to the animal.

Plant-Based Alternatives

A 2019 survey conducted by Mintel reveals that one-quarter of adults in the UK now drink some non-dairy milks (although not always exclusively). It’s even more popular in younger demographics with one-third of 16 to 23-year-olds opting for them.

For the people who want to switch to plant-based alternatives, there are several substitute for dairy milk: oat, soy, almond, and rice milk. We try to rank them based on how greedy each milk produce in utilizing resources, with the first row being the greediest and the last one being the most efficient.

One pattern is consistent in the data: compared with dairy, all of the plant-based alternatives in this comparison have lower impacts across these four measures. In the end, it is really a choice between different environmental trade-offs.

Beyond the metrics, there's another consideration: dairy production directly involves animal welfare concerns that plant-based alternatives avoid. Plant-based alternative may remove the need to keep animals as part of the system of producing milk for human consumption. Our choice therefore involves very different environmental and a real ethical costs behind what we choose to drink: the cost we never really weigh in before.