Milk and its many uses
An introduction to milk
Years ago, a cow’s milk was produced for the sole purpose to be suckled by her calf. Utilisation of cow’s milk as a source of food was well developed by the 19th century with the dairy being an important part of the farm, producing milk, cream, butter and cheese. A good example of a farm dairy can be seen at Acton Scott. Over time cattle have been selected for milk production or beef. Further selection of milking breeds has resulted in greater milk production and selection for different types of milk, most obviously the high fat content of Jersey and Guernsey milk and the lower fat content of Holstein Friesian milk.
Dairy science has developed in parallel with the expansion of the dairy industry, increasing understanding of factors influencing milk production as well as the science of milk production itself. Over time dairy science has led to better understanding and improvement in milk hygiene and milk quality.
The dairy industry is now a huge global industry, valued at US$ 718.9 Billion in 2019 (https://www.imarcgroup.com/global-dairy-market). Whilst in parts of the world production is highly industrialised, in many countries small holders continue to supply much of the milk volume.
Although the main use of milk is for human consumption, it can also be used as a fertility management tool and to monitor aspects of health, either at the individual cow or herd level. Despite its complex matrix, its ease and non- invasive nature of collection means that it is the sample of choice for a range of tests.
Milk can be monitored for levels of progesterone to identify stage of cycle and thus timing of AI, and to identify non-pregnancy after AI. Ridgeway Science produces a farm based penside test P4Rapid and laboratory ELISA, aswell as a milk testing service for progesterone testing.
Similarly, from day 28 of pregnancy, pregnancy-associated glycoproteins (PAG) can be detected in milk by the Idexx milk pregnancy test. Read more about PAG and detection of pregnancy in this paper by Reese ST et al (2017).
Milk samples can be used to monitor health including parameters such as energy balance (https://www.nmr.co.uk/health/energy-balance). It is also possible to monitor disease status for a number of infections including Johnes, liver fluke, Neospora and gastrointestinal nematodes. More information about these tests can be found on the websites for companies offering testing services including:
Some of these tests are individual cow tests, whilst others assess the herd status using bulk milk samples.
This is an incredibly short tour of milk – a substance that has whole journals dedicated to it! We’ll be looking in more detail at some of these aspects of milk and its uses in subsequent articles.