English

Noun

dairies

1. Plural of dairy

A dairy is a facility for the extraction and processing of animal milk—mostly from goats or cows, but also from buffalo, sheep, horses, or camels —for human consumption.

Terminology differs slightly between countries. In particular, in the U.S. a dairy can also be the facility that processes and distributes the milk or the store that sells dairy products, and in New Zealand English a dairy means a corner shop, or Superette—and dairy factory is the term for what is elsewhere a dairy.

As an adjective, the word dairy describes milk-based products, derivatives and processes, for example dairy cattle, dairy goat. A dairy farm produces milk and a dairy factory processes it into a variety of dairy products.

History

Milk-producing animals have been domesticated for thousands of years. Initially they were part of the subsistence farming that nomads engaged in. As the community moved about the country so did their animals accompany them. Protecting and feeding the animals were a big part of the symbiotic relationship between the animal and the herder.

In the more recent past, people in agricultural societies owned dairy animals that they milked for domestic or local (village) consumption, a typical example of a cottage industry. The animals might serve multiple purposes (for example, as a draught animal for pulling a plough as a youngster and at the end of its useful life as meat). In this case the animals were normally milked by hand and the herd size was quite small so that all of the animals could be milked in less than an hour—about 10 per milker.

With industrialisation and urbanisation the supply of milk became a commercial industry with specialised breeds of cow being developed for dairy, as distinct from beef or draught animals. Initially more people were employed as milkers but it soon turned to mechanisation with machines designed to do the milking.

Historically, the milking and the processing took place close together in space and time: on a dairy farm. People milked the animals by hand; on farms where only small numbers are kept hand-milking may still be practiced. Hand-milking is accomplished by grasping the teats (often pronounced tit or tits) in the hand and expressing milk either by squeezing the fingers progressively, from the udder end to the tip, or by squeezing the teat between thumb and index finger then moving the hand downward from udder towards the end of the teat. The action of the hand or fingers is designed to close off the milk duct at the udder (upper) end and, by the movement of the fingers, close the duct progressively to the tip to express the trapped milk. Each half or quarter of the udder is emptied one milk-duct capacity at a time.

The stripping action is repeated, using both hands for speed. Both methods result in the milk that was trapped in the milk duct being squirted out the end into a bucket that is supported between the knees (or rests on the ground) of the milker, who usually sits on a low stool.

Traditionally the cow, or cows, would stand in the field or paddock while being milked. Young stock, heifers, would have to be trained to remain still to be milked. In many countries the cows were tethered to a post and milked. The problem with this method is that it relies on quiet, tractable beasts, because the hind end of the cow is not restrained.

In 1937 it was found that bovine somatotropin (bST) (bovine growth hormone) would increase the yield of milk. Monsanto developed a synthetic version of this hormone. In February 1994 bST was approved by the Food and Drug Administration (FDA) for use in the U.S. It has become common, in the U.S. but not elsewhere, to inject it into milch kine (dairy cows) in order to increase their production by up to 10%. However, there are claims that this practice can have negative consequences for the animals themselves.

Operation of the dairy farm

See dairy farming and dairy cattle for more information.

When it became necessary to milk larger numbers of cows, the cows would be brought to a shed or barn that was set up with bails (stalls) where the cows could be confined while they were milked. One person could milk more cows this way, as many as 20 for a skilled worker. But having cows standing about in the yard and shed waiting to be milked is not good for the cow, as she needs as much time in the paddock grazing as is possible. It is usual to restrict the twice-daily milking to a maximum of an hour and a half each time. It makes no difference whether one milks 10 or 1000 cows, the milking time should not exceed a total of about three hours each day for any cow.

As herd sizes increased there was more need to have efficient milking machines, sheds, milk-storage facilities (vats), bulk-milk transport and shed cleaning capabilities and the means of getting cows from paddock to shed and back.

Farmers found that cows would abandon their grazing area and walk towards the milking area when the time came for milking. This is not surprising as, in the flush of the milking season, cows presumably get very uncomfortable with udders engorged with milk, and the place of relief for them is the milking shed.

As herd numbers increased so did the problems of animal health. In New Zealand two approaches to this problem have been used. The first was improved veterinary medicines (and the government regulation of the medicines) that the farmer could use. The other was the creation of veterinary clubs where groups of farmers would employ a veterinarian (vet) full-time and share those services throughout the year. It was in the vet's interest to keep the animals healthy and reduce the number of calls from farmers, rather than to ensure that the farmer needed to call for service and pay regularly.

Most dairy farmers milk their cows with absolute regularity at a minimum of twice a day, with some high-producing herds milking up to four times a day to lessen the weight of large volumes of milk in the udder of the cow. This daily milking routine goes on for about 300 to 320 days per year that the cow stays in milk. Some small herds are milked once a day for about the last 20 days of the production cycle but this is not usual for large herds. If a cow is left unmilked just once she is likely to reduce milk-production almost immediately and the rest of the season may see her dried off (giving no milk) and still consuming feed for no production. However, once-a-day milking is now being practised more widely in New Zealand for profit and lifestyle reasons. This is effective because the fall in milk yield is at least partially offset by labour and cost savings from milking once per day. This compares to some intensive farm systems in the United States that milk three or more times per day due to higher milk yields per cow and lower marginal labor costs.

Farmers who are contracted to supply liquid milk for human consumption (as opposed to milk for processing into butter, cheese, and so on—see milk) often have to manage their herd so that the contracted number of cows are in milk the year round, or the required minimum milk output is maintained. This is done by mating cows outside their natural mating time so that the period when each cow in the herd is giving maximum production is in rotation throughout the year.

Northern hemisphere farmers who keep cows in barns almost all the year usually manage their herds to give continuous production of milk so that they get paid all year round. In the southern hemisphere the cooperative dairying systems allow for two months on no productivity because their systems are designed to take advantage of maximum grass and milk production in the spring and because the milk processing plants pay bonuses in the dry (winter) season to carry the farmers through the mid-winter break from milking. It also means that cows have a rest from milk production when they are most heavily pregnant. Some year-round milk farms are penalised financially for over-production at any time in the year by being unable to sell their overproduction at current prices.

Artificial insemination (AI) is common in all high-production herds.

Industrial

Main article: dairy products

Cream and butter

Today, milk is separated by large machines in bulk into cream and skim milk. The cream is processed to produce various consumer products, depending on its thickness, its suitability for culinary uses and consumer demand, which differs from place to place and country to country.

Some cream is dried and powdered, some is condensed (by evaporation) mixed with varying amounts of sugar and canned. Most cream from New Zealand and Australian factories is made into butter. This is done by churning the cream until the fat globules coagulate and form a monolithic mass. This butter mass is washed and, sometimes, salted to improve keeping qualities. The residual buttermilk goes on to further processing. The butter is packaged (25 to 50 kg boxes) and chilled for storage and sale. At a later stage these packages are broken down into home-consumption sized packs. Butter sells for about US$3200 a tonne on the international market in 2007 (an unusual high).

Skim milk

The product left after the cream is removed is called skim, or skimmed, milk. Reacting skim milk with rennet or with an acid makes casein curds from the milk solids in skim milk, with whey as a residual. To make a consumable liquid a portion of cream is returned to the skim milk to make low fat milk (semi-skimmed) for human consumption. By varying the amount of cream returned, producers can make a variety of low-fat milks to suit their local market. Other products, such as calcium, vitamin D, and flavouring, are also added to appeal to consumers.

Casein

Casein is the predominant phosphoprotein found in fresh milk. It has a very wide range of uses from being a filler for human foods, such as in ice cream, to the manufacture of products such as fabric, adhesives, and plastics.

Cheese

Cheese is another product made from milk. Whole milk is reacted to form curds that can be compressed, processed and stored to form cheese. In countries where milk is legally allowed to be processed without pasteurisation a wide range of cheeses can be made using the bacteria naturally in the milk. In most other countries, the range of cheeses is smaller and the use of artificial cheese curing is greater. Whey is also the byproduct of this process.

Cheese has historically been an important way of "storing" milk over the year, and carrying over its nutritional value between prosperous years and fallow ones. It is a food product that, with bread and beer, dates back to prehistory in Middle Eastern and European cultures, and like them is subject to innumerable variety and local specificity. Although nowhere near as big as the market for cow's milk cheese, a considerable amount of cheese is made commercially from other milks, especially goat and sheep (see Roquefort cheese for a notable example).

Whey

In earlier times whey was considered to be a waste product and it was, mostly, fed to pigs as a convenient means of disposal. Beginning about 1950, and mostly since about 1980, lactose and many other products, mainly food additives, are made from both casein and cheese whey.

Yogurt

Yoghurt (or yogurt) making is a process similar to cheese making, only the process is arrested before the curd becomes very hard.

Milk powders

Milk is also processed by various drying processes into powders. Whole milk and skim-milk powders for human and animal consumption and buttermilk (the residue from butter-making) powder is used for animal food. The main difference between production of powders for human or for animal consumption is in the protection of the process and the product from contamination. Some people drink milk reconstituted from powdered milk, because milk is about 88% water and it is much cheaper to transport the dried product. Dried skim milk powder is worth about US$5300 a tonne (mid-2007 prices) on the international market.

Other milk products

Kumis is produced commercially in Central Asia. Although it is traditionally made from mare's milk, modern industrial variants may use cow's milk instead.

Transport of milk

Historically, the milking and the processing took place in the same place: on a dairy farm. Later, cream was separated from the milk by machine, on the farm, and the cream was transported to a factory for buttermaking. The skim milk was fed to pigs. This allowed for the high cost of transport (taking the smallest volume high-value product), primitive trucks and the poor quality of roads. Only farms close to factories could afford to take whole milk, which was essential for cheesemaking in industrial quantities, to them. The development of refrigeration and better road transport, in the late 1950s, has meant that most farmers milk their cows and only temporarily store the milk in large refrigerated bulk tanks, whence it is later transported by truck to central processing facilities.

Milking machines

• Cream extraction
• Cheese making
• Buttermaking
• Caseinmaking
• Yogurt processing

Waste disposal

In countries where cows are grazed outside year-round there is little waste disposal to deal with. The most concentrated waste is at the milking shed where the animal waste is liquefied (during the water-washing process) and allowed to flow by gravity, or pumped, into composting ponds with anaerobic bacteria to consume the solids. The processed water and nutrients are then pumped back onto the pasture as irrigation and fertilizer. Surplus animals are slaughtered for processed meat and other rendered products.

In the associated milk processing factories most of the waste is washing water that is treated, usually by composting, and returned to waterways. This is much different from half a century ago when the main products were butter, cheese and casein, and the rest of the milk had to be disposed of as waste (sometimes as animal feed).

In areas where cows are housed all year round the waste problem is difficult because of the amount of feed that is bought in and the amount of bedding material that also has to be removed and composted. The size of the problem can be understood by standing downwind of the barns where such dairying goes on.

In many cases modern farms have very large quantities of milk to be transported to a factory for processing. If anything goes wrong with the milking, transport or processing facilities it can be a major disaster trying to dispose of enormous quantities of milk. If a road tanker overturns on a road the rescue crew is looking at accommodating the spill of 10 to 20 thousand gallons of milk (45 to 90 thousand litres) without allowing any into the waterways. A derailed rail tanker-train may involve 10 times that amount. Without refrigeration, milk is a fragile commodity and it is very damaging to the environment in its raw state. A widespread electrical power blackout is another disaster for the dairy industry because both milking and processing facilities are affected.

In dairy-intensive areas the simplest way of disposing of large quantities of milk has been to dig a large hole in the ground and allow the clay to filter the milk solids as it soaks away. This is not very satisfactory.

Associated diseases

Mastitis can also be a common disease found in milk which cause it to go off very quickly and has a horrible sour taste.

• Leptospirosis is one of the most common debilitating diseases of milkers, made somewhat worse since the introduction of herringbone sheds because of unavoidable direct contact with bovine urine
• Cowpox is one of the helpful diseases; it is barely harmful to humans and tends to inoculate them against other poxes such as chickenpox
• Tuberculosis (TB) is able to be transmitted from cattle (myth!) mainly via milk products that are unpasteurised and many dairy-producing families consume milk that way. In the important dairy exporting countries TB has been eradicated from herds by testing for the disease and culling suspected animals
• Brucellosis is a bacterial disease transmitted to humans by dairy products and direct animal contact. In the important dairy exporting countries Brucellosis has been eradicated from herds by testing for the disease and culling suspected animals
• Listeria is a bacterial disease associated with unpasteurised milk and can affect some cheeses made in traditional ways. Careful observance of the traditional cheesemaking methods achieves reasonable protection for the consumer
• Johne's Disease (pronounced "yo-knees") is a contagious, chronic and usually fatal infection in ruminants caused by a bacterium named Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis). The bacteria is present in retail milk and is believed by some researchers to be the primary cause of Crohn's disease in humans. This disease is not known to infect animals in Australia and New Zealand.

Notes

References

• Jay, J.M. (1992). Modern Food Microbiology. Fourth Edition. New York: Chapman & Hall. pp. 237-9.
• Potter, N.N. & J. H. Hotchkiss. (1995). Food Science. Fifth Edition. New York: Chapman & Hall. pp. 279-315.
• Swasigood, H.E. (1985). "Characteristics of Edible Fluids of Animal Origin: Milk." In Food Chemistry. Second Edition. Revised and Expanded. O.R. Fennema, Ed. New York: Marcell Dekker, Inc. pp. 791-827.

External links

• Dairy Council of California
• National Dairy Council
• Milk Development Council - UK
• Milking in the early days
• National Dairy Research Institute
• Milk Development Council - UK
• Read Congressional Research Service (CRS) Reports regarding the Dairy Industry
• Ontario Ministry of Agriculture, Food and Rural Affairs - Dairy Housing Advice
• University of Guelph Dairy Science and Technology Education Series -- Online technical information about dairy products.
• Dairy Science and Food Technology: Starters, Probiotics, Cheese and Antimicrobial Systems
• PETA page on the Health Risks of Dairy
• Dairy research and information from New Zealand
• Dairy water heating technologies in NZ
• Perspectives on Dairy by Gabriel Cousens M.D.,M.D.(H) - The Vegan Angle
• Housing the Modern Dairy Cow
• The story of barbed wire is intimately bound up in dairying
• National Dairy Herd Improvement Assoc
• Dairy Market review