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A rotary milking parlor

Dairy farming is a class of agricultural, or an animal husbandry, enterprise, for long-term production of milk, usually from dairy cows but also from goats and sheep, which may be either processed on-site or transported to a dairy factory for processing and eventual retail sale.

Most dairy farms sell the male calves born by their cows, usually for veal production, or breeding depending on quality of the bull calf, rather than raising non-milk-producing stock.[citation needed] Many dairy farms also grow their own feed, typically including corn, alfalfa, and hay. This is fed directly to the cows, or is stored as silage for use during the winter season. Additional dietary supplements are often added to the feed to increase quality milk production.

Contents

History

Woman hand milking a cow

Dairy farming has been part of agriculture for thousands of years. Historically it has been one part of small, diverse farms. In the last century or so larger farms doing only dairy production have emerged. Large scale dairy farming is only viable where either a large amount of milk is required for production of more durable dairy products such as cheese, or there is a substantial market of people with cash to buy milk, but no cows of their own.

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Hand milking

Centralized dairy farming as we understand it primarily developed around villages and cities, where residents were unable to have cows of their own due to a lack of grazing land. Near the town, farmers could make some extra money on the side by having additional animals and selling the milk in town. The dairy farmers would fill barrels with milk in the morning and bring it to market on a wagon. Until the late 1800s, the milking of the cow was done by hand. In the United States, several large dairy operations existed in some northeastern states and in the west, that involved as many as several hundred cows, but an individual milker could not be expected to milk more than a dozen cows a day. Smaller operations predominated.

Milking took place indoors in a barn with the cattle tied by the neck with ropes or held in place by stanchions. Feeding could occur simultaneously with milking in the barn, although most dairy cattle were pastured during the day between milkings. Such examples of this method of dairy farming are difficult to locate, but some are preserved as a historic site for a glimpse into the days gone by. One such instance that is open for this is at Point Reyes National Seashore.[1]

Vacuum bucket milking

Demonstration of a new Soviet milker device. East Germany, 1952

The first milking machines were an extension of the traditional milking pail. The early milker device fit on top of a regular milk pail and sat on the floor under the cow. Following each cow being milked, the bucket would be dumped into a holding tank. This developed into the Surge hanging milker. Prior to milking a cow, a large wide leather strap called a surcingle was put around the cow, across the cow's lower back. The milker device and collection tank hung underneath the cow from the strap. This innovation allowed the cow to move around naturally during the milking process rather than having to stand perfectly still over a bucket on the floor.

With the availability of electric power and suction milking machines, the production levels that were possible in stanchion barns increased but the scale of the operations continued to be limited by the labor intensive nature of the milking process. Attaching and removing milking machines involved repeated heavy lifting of the machinery and its contents several times per cow and the pouring of the milk into milk cans. As a result, it was rare to find single-farmer operations of more than 50 head of cattle.

Step-Saver milk transport

As herd size began to increase, the bucket milker system became laborious. A vacuum milk-transport system known as the Step-Saver was developed to transport milk to the storage tank. The system used a long vacuum hose coiled around a receiver cart, and connected to a vacuum-breaker device in the milkhouse, allowing farmers to milk many cows without the necessity of walking increasingly longer distances carrying heavy buckets of milk.

Milking pipeline

The next innovation in automatic milking was the milk pipeline. This uses a permanent milk-return pipe and a second vacuum pipe that encircles the barn or milking parlor above the rows of cows, with quick-seal entry ports above each cow. By eliminating the need for the milk container, the milking device shrank in size and weight to the point where it could hang under the cow, held up only by the sucking force of the milker nipples on the cow's udder. The milk is pulled up into the milk-return pipe by the vacuum system, and then flows by gravity to the milkhouse vacuum-breaker that puts the milk in the storage tank. The pipeline system greatly reduced the physical labor of milking since the farmer no longer needed to carry around huge heavy buckets of milk from each cow.

The pipeline allowed barn length to keep increasing and expanding, but after a point farmers started to milk the cows in large groups, filling the barn with one-half to one-third of the herd, milking the animals, and then emptying and refilling the barn. As herd sizes continued to increase, this evolved into the more efficient milking parlor.

Milking parlors

Innovation in milking focused on mechanising the milking parlour to maximise throughput of cows per operator which streamlined the milking process to permit cows to be milked as if on an assembly line, and to reduce physical stresses on the farmer by putting the cows on a platform slightly above the person milking the cows to eliminate having to constantly bend over. Many older and smaller farms still have tie-stall or stanchion barns, but worldwide a majority of commercial farms have parlours.

The milking parlor allowed a concentration of money into a small area, so that more technical monitoring and measuring equipment could be devoted to each milking station in the parlor. Rather than simply milking into a common pipeline for example, the parlor can be equipped with fixed measurement systems that monitor milk volume and record milking statistics for each animal. Tags on the animals allow the parlor system to automatically identify each animal as it enters the parlor.

Recessed parlors

More modern farms use recessed parlors, where the milker stands in a recess such that his arms are at the level of the cow's udder. Recessed parlors can be herringbone, where the cows stand in two angled rows either side of the recess and the milker accesses the udder from the side, parallel, where the cows stand side-by-side and the milker accesses the udder from the rear or, more recently, rotary (or carousel), where the cows are on a raised circular platform, facing the center of the circle, and the platform rotates while the milker stands in one place and accesses the udder from the rear. There are many other styles of milking parlors which are less common.

Herringbone and parallel parlors

In herringbone and parallel parlors, the milker generally milks one row at a time. The milker will move a row of cows from the holding yard into the milking parlor, and milk each cow in that row. Once all or most of the milking machines have been removed from the milked row, the milker releases the cows to their feed. A new group of cows is then loaded into the now vacant side and the process repeats until all cows are milked. Depending on the size of the milking parlor, which normally is the bottleneck, these rows of cows can range from four to sixty at a time.

Rotary parlors

In rotary parlors, the cows are loaded one at a time onto the platform as it slowly rotates. The milker stands near the entry to the parlor and puts the cups on the cows as they move past. By the time the platform has completed almost a full rotation, another milker or a machine removes the cups and the cow steps backwards off the platform and then walks to its feed.

Automatic milker take-off

It can be harmful to an animal for it to be over-milked past the point where the udder has stopped releasing milk. Consequently the milking process involves not just applying the milker, but also monitoring the process to determine when the animal has been milked out and the milker should be removed. While parlor operations allowed a farmer to milk many more animals much more quickly, it also increased the number of animals to be monitored simultaneously by the farmer. The automatic take-off system was developed to remove the milker from the cow when the milk flow reaches a preset level, relieving the farmer of the duties of carefully watching over 20 or more animals being milked at the same time.

Fully automated robotic milking

In the 1980s and 1990s, robotic milking systems were developed and introduced (principally in the EU). Thousands of these systems are now in routine operation. In these systems the cow has a high degree of autonomy to choose her time of milking within pre-defined windows. These systems are generally limited to intensively managed systems although research continues to match them to the requirements of grazing cattle and to develop sensors to detect animal health and fertility automatically.

History of milk preservation methods

Cool temperature has been the main method by which milk freshness has been extended. When windmills and well pumps were invented, one of its first uses on the farm besides providing water for animals was for cooling milk, to extend the storage life before being transported to the town market.

The naturally cold underground water would be continuously pumped into a tub or other containers of milk set in the tub to cool after milking. This method of milk cooling was extremely popular before the arrival of electricity and refrigeration.

Refrigeration

When refrigeration first arrived (the 19th century) the equipment was initially used to cool cans of milk, which were filled by hand milking. These cans were placed into a cooled water bath to remove heat and keep them cool until they were able to be transported to a collection facility. As more automated methods were developed for harvesting milk, hand milking was replaced and, as a result, the milk can was replaced by a bulk milk cooler. 'Ice banks' were the first type of bulk milk cooler. This was a double wall vessel with evaporator coils and water located between the walls at the bottom and sides of the tank. A small refrigeration compressor was used to remove heat from the evaporator coils. Ice eventually builds up around the coils, until it reaches a thickness of about three inches surrounding each pipe, and the cooling system shuts off. When the milking operation starts, only the milk agitator and the water circulation pump, which flows water across the ice and the steel walls of the tank, are needed to reduce the incoming milk to a temperature below 40 degrees.

This cooling method worked well for smaller dairies, however was fairly inefficient and was unable to meet the increasingly higher cooling demand of larger milking parlors. In the mid 1950's direct expansion refrigeration was first applied directly to the bulk milk cooler. This type of cooling utilizes an evaporator built directly into the inner wall of the storage tank to remove heat from the milk. Direct expansion is able to cool milk at a much faster rate than early ice bank type coolers and is still the primary method for bulk tank cooling today on small to medium sized operations.

Another device which has contributed significantly to milk quality is the plate heat exchanger (PHE). This device utilizes a number of specially designed stainless steel plates with small spaces between them. Milk is passed between every other set of plates with water being passed between the balance of the plates to remove heat from the milk. This method of cooling can remove large amounts of heat from the milk in a very short time, thus drastically slowing bacteria growth and thereby improving milk quality. Ground water is the most common source of cooling medium for this device. Dairy cows consume approximately 3 gallons of water for every gallon of milk production and prefer to drink slightly warm water as opposed to cold ground water. For this reason, PHE's can result in drastically improved milk quality, reduced operating costs for the dairymen by reducing the refrigeration load on his bulk milk cooler, and increased milk production by supplying the cows with a source of fresh warm water.

Plate heat exchangers have also evolved as a result of the increase of dairy farm herd sizes in the US. As a dairyman increases the size of his herd, he must also increase the capacity of his milking parlor in order to harvest the additional milk. This increase in parlor sizes has resulted in tremendous increases in milk throughput and cooling demand. Today's larger farms produce milk at a rate which direct expansion refrigeration systems on bulk milk coolers cannot cool in a timely manner. PHE's are typically utilized in this instance to rapidly cool the milk to the desired temperature (or close to it) before it reaches the bulk milk tank. Typically, ground water is still utilized to provide some initial cooling to bring the milk to between 55 and 70 degrees F. A second (and sometimes third) section of the PHE is added to remove the remaining heat with a mixture of chilled pure water and propylene glycol. These chiller systems can be made to incorporate large evaporator surface areas and high chilled water flow rates to cool high flow rates of milk.

Milking operation

Milking machines are held in place automatically by a vacuum system that draws the ambient air pressure down from 15 to 21 pounds of vacuum. The vacuum is also used to lift milk vertically through small diameter hoses, into the receiving can. A milk lift pump draws the milk from the receiving can through large diameter stainless steel piping, through the plate cooler, then into a refrigerated bulk tank.

Milk is extracted from the cow's udder by flexible rubber sheaths known as liners or inflations that are surrounded by a rigid air chamber. A pulsating flow of ambient air and vacuum is applied to the inflation's air chamber during the milking process. When ambient air is allowed to enter the chamber, the vacuum inside the inflation causes the inflation to collapse around the cow's teat, squeezing the milk out of teat in a similar fashion as a baby calf's mouth massaging the teat. When the vacuum is reapplied in the chamber the flexible rubber inflation relaxes and opens up, preparing for the next squeezing cycle.

It takes the average cow three to five minutes to give her milk. Some cows are faster or slower. Slow-milking cows may take up to fifteen minutes to let down all their milk. Milking speed is only minorly related to the quantity of milk the cow produces — milking speed is a separate factor from milk quantity; milk quantity is not determinative of milking speed. Because most milkers milk cattle in groups, the milker can only process a group of cows at the speed of the slowest-milking cow. For this reason, many farmers will cull slow-milking cows.

The extracted milk passes through a strainer and plate heat exchangers before entering the tank, where it can be stored safely for a few days at approximately 3 °C or around 42 °F (6 °C). At pre-arranged times, a milk truck arrives and pumps the milk from the tank for transport to a dairy factory where it will be pasteurized and processed into many products.

Animal waste from large dairies

Dairy CAFO - EPA

As measured in phosphorus, the waste output of 5,000 cows roughly equals a municipality of 70,000 people.[2] In the U.S., dairy operations with more than 1,000 cows meet the EPA definition of a CAFO (Concentrated Animal Feeding Operation), and are subject to EPA regulations.[3] For example, in the San Joaquin Valley of California a number of dairies have been established on a very large scale. Each dairy consists of several modern milking parlor set-ups operated as a single enterprise. Each milking parlor is surrounded by a set of 3 or 4 loafing barns housing 1,500 or 2,000 cattle. Some of the larger dairies have planned 10 or more series of loafing barns and milking parlors in this arrangement, so that the total operation may include as many as 15,000 or 20,000 cows. The milking process for these dairies is similar to a smaller dairy with a single milking parlor but repeated several times. The size and concentration of cattle creates major environmental issues associated with manure handling and disposal, which requires substantial areas of cropland (a ratio of 5 or 6 cows to the acre, or several thousand acres for dairies of this size) for manure spreading and dispersion, or several-acre methane digesters. Air pollution from methane gas associated with manure management also is a major concern. As a result, proposals to develop dairies of this size can be controversial and provoke substantial opposition from environmentalists including the Sierra Club and local activists.[4][5]

The potential impact of large dairies was demonstrated when a massive manure spill occurred on a 5,000-cow dairy in Upstate New York, contaminating a 20-mile (32 km) stretch of the Black River, and killing 375,000 fish. On Aug. 10, 2005, a manure storage lagoon collapsed releasing several million gallons of manure into the Black River. Subsequently the New York Department of Environmental Conservation mandated a settlement package of $2.2 million against the dairy.[2]

Use of hormones

It is possible to maintain higher milk production by injecting cows with growth hormones known as recombinant BST or rBGH, but this is controversial due to its effects on animal and possibly human health. The European Union, Japan, Australia, New Zealand and Canada have banned its use[6][7] due to these concerns. However, no such prohibition exists in the US, where approximately 17.2% of dairy cows are treated in this way.[8] The U.S. Food and Drug Administration states that no "significant difference" has been found between milk from treated and non-treated cows[9] but based on consumer concerns several milk purchasers and resellers have elected not to purchase milk produced with rBST. [10][11] [11] [12] [13]

Management of the herd

Modern dairy farmers use milking machines and sophisticated plumbing systems to harvest and store the milk from the cows, which are usually milked two or three times daily. During the warm months, in the northern hemisphere, cows may be allowed to graze in their pastures, both day and night, and are brought into the barn only to be milked. Many barns also incorporate tunnel ventilation into the architecture of the barn structure. This ventilation system is highly efficient and involves opening both ends of the structure allowing cool air to blow through the building. Farmers with this type of structure keep cows inside during the summer months to prevent sunburn and damage to udders. During the winter months, especially in northern climates, the cows may spend the majority of their time inside the barn, which is warmed by their collective body heat. Even in winter, the heat produced by the cattle requires the barns to be ventilated for cooling purposes. Many modern facilities, and particularly those in tropical areas, keep all animals inside at all times to facilitate herd management. Housing the cow can be either loose housed or stalls (called cow cubicles in UK). There is little research available on dimensions required for cow stalls, and much housing can be out of date, however increasingly companies are making farmers aware of the benefits, in terms of animal welfare, health and milk production.

In the southern hemisphere cows spend most of their lives outside on pasture, although they may receive supplementation during periods of low pasture availabliity.[14]

The production of milk requires that the cow be in lactation, which is a result of the cow having given birth to a calf. The cycle of insemination, pregnancy, parturition, and lactation, followed by a "dry" period of a few weeks before calving which allows udder tissue to regenerate. Dairy operations therefore include both the production of milk and the production of calves. Bull calves are either castrated and raised as steers for beef production or veal.

Health and well-being

Common ailments affecting dairy cows include infectious disease (e.g. mastitis, endometritis and digital dermatitis), metabolic disease (e.g. milk fever and ketosis) and injuries caused by their environment (e.g. hoof and hock lesions). [15]

Lameness is commonly considered one of the most significant animal welfare issues for dairy cattle. [16][17][18][19] It can be caused by a number of sources, including infections of the hoof tissue (e.g. fungal infections that cause dermatitis) and physical damage causing bruising or lesions (e.g. ulcers or hemorrhage of the hoof).[20] While housing and management features common in modern conventional dairy farms (such as concrete barn floors, limited access to pasture and suboptimal bed-stall design) have been identified as contributing risk factors[21], small farms in developing countries can also demonstrate high rates.[22]

Market

Holstein cows on a dairy farm, Comboyne, New South Wales

India is the largest producer of dairy products in the world. There is a great deal of variation in the pattern of dairy production worldwide. Many countries which are large producers, consume this internally, while others — in particular New Zealand — export a large percentage of their production. Internal consumption is often in the form of liquid milk, while the bulk of international trade is in processed dairy products such as milk powder.

The world's largest exporter of dairy products is New Zealand,[23] and dairy products are the largest export earner for the country.[24] Fonterra is the fifth-largest dairy company in the world and New Zealand's largest company by turnover,

Japan is the world's largest importer of dairy products.

World production
Rank Country Production (109kg/y)[25]
1  India 114.4
2  United States 79.3
3  Germany 39.4
4  Pakistan 35.2
5  China 32.5
6  Russia 28.5
7  Brazil 26.2
8  France 24.2
9  New Zealand 17.3
10  United Kingdom 13.9
11  Ukraine 12.2
12  Poland 12
13  Netherlands 11.5
14  Italy 11.0
15  Turkey 10.6
16  Mexico 10.2
17  Australia 9.6
18  Egypt 8.7
19  Argentina 8.5
20  Canada 8.1

European Union

The European Union is the largest milk producer in the world, with 143.7 million tonnes in 2003. This data, encompassing the present 25 member countries, can be further broken down into the production of the original 15 member countries, with 122 million tonnes, and the new 10 mainly former Eastern European countries with 21.7 million tonnes.

Dairy production is heavily distorted due to the Common Agricultural Policy—being subsidized in some areas, and subject to production quotas in other.

Rank Country Production (109kg/y)[26]
1  Germany 28.5
2  France 24.6
3  United Kingdom 15.0
4  Poland 11.9
5  Netherlands 11.0
6  Italy 10.8
7  Spain 6.6
8  Ireland 5.4
9  Denmark 4.7
10  Sweden 3.2
11  Austria 3.2
12  Belgium 3.1
13  Czech Republic 2.7
14  Finland 2.5
15  Hungary 1.9
16  Portugal 1.9
17  Lithuania 1.8

United States

In the United States, the top four dairy states are, in order by total milk production; California, Wisconsin, New York, and Idaho. Dairy farming is also an important industry in Florida, Minnesota, Ohio and Vermont.[27] There are 65,000 dairy farms in the United States.[28]

Pennsylvania however, is the state with the heaviest dependence on dairy farming — there it is the number one industry. Pennsylvania is home to 8,500 farms and 555,000 dairy cows. Milk produced in Pennsylvania yields about US$1.5 billion in farm revenue every year, and is sold to various states up and down the east coast.[29]

Milk prices collapsed in 2009. Senator Bernie Sanders accused Dean Foods of controlling 40% of the country's milk market. He has requested the United States Department of Justice to pursue `an anti-trust investigation.[30] Dean Foods says it buys 15% of the country's raw milk.[31]

Competition

Most milk-consuming countries have a local dairy farming industry, and most producing countries maintain significant subsidies and trade barriers to protect domestic producers from foreign competition[citation needed]. In large countries, dairy farming tends to be geographically clustered in regions with abundant natural water supplies (both for feed crops and for cattle)[citation needed] and relatively inexpensive land (even under the most generous subsidy regimes, dairy farms have poor return on capital). New Zealand, the fourth largest dairy producing country, does not apply any subsidies to dairy production. [32]

The milking of cows was traditionally a labor-intensive operation and still is in less developed countries. Small farms need several people to milk and care for only a few dozen cows, though for many farms these employees have traditionally been the children of the farm family, giving rise to the term "family farm".

Advances in technology have mostly led to the radical redefinition of "family farms" in industrialized countries such as the United States. With farms of hundreds of cows producing large volumes of milk, the larger and more efficient dairy farms are more able to weather severe changes in milk price and operate profitably, while "traditional" very small farms generally do not have the equity or cash flow to do so. The common public perception of large corporate farms supplanting smaller ones is generally a misconception, as many small family farms expand to take advantage of economies of scale, and incorporate the business to limit the legal liabilities of the owners and simplify such things as tax management.[citation needed]

Before large scale mechanization arrived in the 1950s, keeping a dozen milk cows for the sale of milk was profitable.[citation needed] Now most dairies must have more than one hundred cows being milked at a time in order to be profitable, with other cows and heifers waiting to be "freshened" to join the milking herd . In New Zealand the average herd size, depending on the region, is about 350 cows.[citation needed]

Herd size in the US varies between 1,200 on the West Coast and Southwest, where large farms are commonplace, to roughly 50 in the Northeast, where land-base is a significant limiting factor to herd size. The average herd size in the U.S. is about one hundred cows per farm.[citation needed]

Currently, concerns regarding monopolies created by Dean Foods, Kraft, and other major buyers of bulk dairy products on the Chicago Mercantile Exchange have been raised, as American dairy farms have suffered extreme price depression and chaotic fluctuations while processors and retailers report record profits. Many theorize that unregulated imports of milk protein concentrate used by processors to boost cheese yield has artificially and unfairly influenced the markets in an effort to force consolidation and vertical integration in what has historically been a highly diversified industry.

See also

References

  1. ^ Public tours
  2. ^ a b "DEC Reports: Progress since Marks Dairy Spill". New York State Department of Environmental Conservation. 2007-08-09. http://www.dec.ny.gov/press/36942.html. Retrieved 2008-09-26. 
  3. ^ "Regulatory Definitions of Large CAFOs, Medium CAFO, and Small CAFOs" (PDF). United States Environmental Protection Agency. http://www.epa.gov/npdes/pubs/sector_table.pdf. Retrieved 2008-09-26. 
  4. ^ "Joseph Gallo Dies". Merced Sun-Star. http://www.mercedsunstar.com/local/story/13311227p-13939012c.html. Retrieved 2008-09-26. 
  5. ^ "Total Integration". Joseph Farms. http://www.josephfarms.com/index.php?page=total_integration. Retrieved 2008-09-26. 
  6. ^ "Say No to rBGH!". Fodd and Water Watch. http://www.foodandwaterwatch.org/food/foodsafety/dairy/no-rbgh. Retrieved 2008-09-26. 
  7. ^ "We're drinking WHAT? U.S. consumers reject milk adulterated with Monsanto's rBST". Onlinejournal.com. http://onlinejournal.com/artman/publish/article_1447.shtml. Retrieved 2009-08-10. 
  8. ^ "Dairy 2007 Part II: Changes in the U.S. Dairy Cattle Industry, 1991–2007" (PDF). Animal and Plant Health Inspection Service. March 2007. http://www.aphis.usda.gov/vs/ceah/ncahs/nahms/dairy/dairy07/Dairy2007_PartII.pdf. Retrieved 2010-01-27. 
  9. ^ "FDA Warns Milk Producers to Remove "Hormone Free" Claims From the Labeling Of Dairy Products". U.S. Food and Drug Administration. 2003-02-12. http://www.cfsan.fda.gov/~lrd/fprbst.html. Retrieved 2008-09-26. 
  10. ^ "Safeway milk free of bovine hormone". Seattle Post-Intelligencer (via AP). 2007-01-22. http://seattlepi.nwsource.com/business/300596_safeway22.html. Retrieved 2008-04-04. 
  11. ^ a b North, R (2007-01-10). "Safeway & Chipotle Chains Dropping Milk & Dairy Derived from Monsanto's Bovine Growth Hormone". Oregon Physicians for Social Responsibility. http://www.organicconsumers.org/articles/article_3773.cfm. Retrieved 2008-01-29. 
  12. ^ "Kroger to complete transition to certified rBST-free milk by early 2008 (press release)". Kroger. 2007. http://www.thekrogerco.com/corpnews/corpnewsinfo_pressreleases_08012007.htm. Retrieved 2008-01-29. 
  13. ^ "Statement and Q&A-Starbucks Completes its Conversion – All U.S. Company-Operated Stores Use Dairy Sourced Without the Use of rBGH". Starbucks Corporation. http://www.starbucks.com/aboutus/pressdesc.asp?id=819. Retrieved 2008-04-04. 
  14. ^ Shaw, John H., Collins, Australian Encyclopedia, Collins, Sydney, 1984, ISBN 000217315-8
  15. ^ Rushen, J., de Passillé, A. M., von Keyserlingk, M. A. G., & Weary, D. M. (2008). The welfare of cattle. Animal Welfare Vol. 5. Berlin: Springer Verlag. pp. 21-35.
  16. ^ ibid
  17. ^ Fraser, A.F. and D.M/ Broom. 1990. Farm Animal Welfare and Behaviour (3rd ed.) London: Bailliere Tindall. pp.355-356.
  18. ^ Greenough, P.R. Bovine Laminitis and Lameness: A Hands-On Approach. 2007. Edinburgh: Saunders. p.3.
  19. ^ Invited review: the welfare of dairy cattle—Key conceptsand the role of science. M.A.G. von Keyserlingk, J. Rushen, A.M. de Passillé, and D.M. Weary. J. Dairy Sci. 92 :4101–4111.
  20. ^ ibid
  21. ^ Cook, N.B., and K.V. Nordlund. 2009. Review: The influence of the environment on dairy cow behavior, claw health and herd health lameness dynamics. Vet. J. 179:360–369.
  22. ^ Gitau, T, McDermott, J.J. and Mbiuki, S.M. 1996. Prevalence, incidence and risk factors for lameness in dairy cattle in small-scale farms inkikuyu division, Kenya. Preventive Veterinary Medicine. 28: 101-115.
  23. ^ Evans, Gavin (2008-08-04). "N.Z. Forecasts Fall in Dairy Prices Through 2009". Bloomberg.com. http://www.bloomberg.com/apps/news?pid=20601081&sid=a4O5KrquIb90. Retrieved 2008-09-26. 
  24. ^ dead link] "New Zealand Dairy Industry". MarketNewZealand.com. http://www.marketnewzealand.com/MNZ/aboutNZ/sectors/14713.aspx. Retrieved 2008-09-26. 
  25. ^ [1]
  26. ^ Production of cow's milk and milk deliveries to dairies, European union by country, MDC Datum, 2003, http://www.mdcdatum.org.uk/MilkSupply/euproduction.html, retrieved 2007-10-29 
  27. ^ "Farm Level Production" (PDF). International Dairy Foods Association. 2004. http://www.idfa.org/facts/milk/milkfact/2004_milk_production.pdf. Retrieved 2008-09-26. 
  28. ^ "Congressional caucus formed to address dairy policy". Southwest Farm Press. April 06, 2006. http://southwestfarmpress.com/news/06-04-06-caucua-formed-dairy. 
  29. ^ "Overview of Pennsylvania's Dairy Industry". Center for Dairy Excellence. http://www.centerfordairyexcellence.org/index.php/pennsylvania-dairy-industry-overview.html. Retrieved 2008-09-26. 
  30. ^ McLean, Dan (28 July 2009). "Dean Foods snubs Sanders". Burlington, Vermont: Burlington Free Press. pp. 1A. 
  31. ^ "Milk processors under fire". Burlington, Vermont: Burlington Free Press. 20 September 2009. pp. 1B. 
  32. ^ http://www.cato.org/pub_display.php?pub_id=3411

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