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Milk and dairy production

Dairy cows are bred specifically for their high milk producing capacity. In this article we explore the full milk production process.
© EIT Food

Dairy cows produce milk which is in high demand from consumers as fresh milk, or processed dairy products such as cheese, butter and yoghurt. There were an estimated 274 million dairy cows in the world in 2016 [1], with India and the USA producing a large fraction of the world’s milk (20% and 12% respectively) [1]. (Take a look at the link in the ‘See Also’ section at the bottom of this article for an infographic from the FAO showing milk production by country and how it has changed over the last 3 decades.)

Milk production cycle

Dairy cows are specialised breeds of cattle with high capacity for milk production. The typical dairy cow production cycle is shown in the diagram below. A young female cow known as a heifer gives birth to its first calf at approximately 24 months of age. After calving the heifer becomes a lactating (milking) cow. The average length of the period in milk is 10 months, followed by a 2 month ‘dry’ or resting period before the cow has the next calf.

Growing period: Birth, Weaning ~6-8 weeks, Breeding (with bull or artificial insemination) ~15 months, First Calving at ~24 months. Lactation (milking) period with the aim of having one calendar year between calvings: Pregnancy: breeding when cow returns to heat (pregnancy), Pregnancy: Dry period (not milking), Calving at ~10 months after successful breeding, Cycle repeats

Figure 2: Milk production cycle

Dairy cows are typically milked twice per day in a milking parlour, using milking machinery which delivers the milk directly to a bulk collection tank. The bulk tank cools and maintains the milk at 3–4°C before it is collected by a tanker [3]. The tanker then delivers the milk to a milk processor to be pasteurised. A modern, high yielding dairy cow produces an average of 7,800 litres of milk per year, although this is influenced by many factors including breed and production system [4].

Milking machines attached to cows in individual compartments

Figure 3: Milking parlour at the University of Reading’s farm. A clean environment is vital to meet hygiene standards.

How milk is produced

Due to the long lifecycle of a dairy cow, it is important to understand how the production system may affect the welfare of the animal and the productivity of the farm. There are two common yet contrasting systems of dairy production:

  • outdoor grass-based and
  • continuous indoor housed.

The grass-based system relies on grassland being available for grazing for much of the year. In the continuous indoor housed system, milking cows remain inside purpose-built barns throughout the year [5]. They are provided with individual bays to lie in, and a feeding barrier to access feed and water.

Cows feeding

Figure 4: Dairy cows feeding on silage at a feeding barrier in an indoor-based system at University of Reading’s farm. Diet is carefully formulated, and cows closely monitored to ensure optimal body condition and health is maintained.

Both systems have advantages and disadvantages which are summarised in the table below:

  Grass based system Continuously housed system
Advantages Lower production costs [4]. Allows cows to exhibit natural feeding and social behaviours [9]. Contributes to ecosystem functions, eg through nutrient recycling, and in turn may benefit soil, biodiversity and wildlife [6]. Higher milk yields than grass-based: achievable milk yields 9000-10000 litres/cow/year. Easier control of energy and nutrient intakes for optimal health and production. Easier monitoring of health; disease prevention and control.
Disadvantages Lower milk yields than continuously housed: achievable milk yields 4000-5000 litres/cow/year [3]. Land availability suitable for grazing may be limiting. Lower profit margins despite lower costs (due to lower yield). Weather and climatic conditions affect the quality of pasture and success of grazing. Higher production costs (eg high feed costs), but usually offset by higher yields. Higher dependency on intensified crop production and its associated effects (use of agro-chemicals, biodiversity loss, soil degradation). High capital investment and reliance on mechanisation and industrial techniques.
Table 1: Advantages and disadvantages of grass-based and continuously housed systems

Sustainability Challenges

From a welfare point of view, managing the feeding and health of dairy cows is one of the most critical factors for a successful dairy farm. The dietary needs of dairy cows change through the production cycle and so each cow must be carefully monitored to ensure they have optimal energy and nutrient intakes to be healthy and productive.

The contribution of ruminant livestock production to greenhouse gas emissions is increasingly highlighted [7] and scientists and farmers are working together to find ways to reduce the environmental impact of the dairy industry [8].

And finally, the economic viability of dairy farming has become increasingly challenging in recent years. The 5-year rolling average milk price in the UK is 27.2 pence per litre (ppl). Taking all the costs into account, for the top 25% of UK milk producers, it costs 26.7 ppl to produce. For the bottom 25% of producers, it costs 36.6 ppl to produce [10]. Margins on milk production are therefore very tight and many farmers have ceased keeping a dairy herd as a result.

References can be found under the ‘Downloads’ heading at the bottom of this Step.


In the UK, in 1995 there were approximately 35,741 dairy farmers. In 2018 there were 8,991 dairy farmers. This trend is seen in other developed countries including the USA and European countries.

  • Why do you think this change has occurred?
  • What do you think might be the consequences of this change?
© EIT Food
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