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woman hand milking a cow.

Dairy farming

Dairy farming is a class of agricultural , or an animal husbandry , enterprise, for long-termproduction of milk , usually from dairy cows but also from goats , sheep and camels , which may be either processed on-site or transported to a dairy factory for processing and eventual retail sale.
Most dairy farms sell themale calves born by theircows, usually for veal production, or breeding depending on quality of the bull calf, rather than raising non-milk-producing stock. Many dairy farms also grow their own feed, typically including corn , and hay . This is fed directly to the cows, or is stored as silage for use during the winter season.

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 , butter, etc. or there is a substantial market of people with cash to buy milk, but no cows of their own.

Centralized dairy farmingas 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 animalsand selling the milk in town. The dairy farmerswould fill barrels with milk in the morning and bring it to market on a wagon. Until the late 19th century, the milkingof 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.
For most herds, milking took place indoors twice a day, [ 1 ] 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 .

Vacuum bucketmilking

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 beingmilked, the bucket wouldbe dumped into a holdingtank. This developed intothe 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.

The next innovation in automatic milking was the milk pipeline. This uses a permanent milk-return pipe and a second vacuum pipe thatencircles 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 hangunder the cow, held up only by the sucking forceof 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 barnlength to keep increasingand expanding, but aftera 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 herdsizes continued to increase, this evolved into the more efficient milking parlor.
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 sideand the process repeats until all cows are milked. Depending on the size ofthe milking parlor, which normally is the bottleneck, these rows of cows can range from four to sixty at a time.

In rotary parlors , the cows are loaded one at atime onto the platform as it slowly rotates. Themilker 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 walksto its feed. Rotary cowsheds, as they are called in New Zealand, started in the 1980s [ 3 ] [ 4 ] but are expensive compared to Herringbonecowshed - the older NewZealand norm. [ 5 ] To justify the costs herds have got bigger with 1 person milking 500-600 cows. [ citation needed ] A rotary is about 25% faster than a herringbone shed for thesame number of cows.

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. Whileparlor operations alloweda 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 themilker 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.This is a standard procedure in New Zealand

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 animalhealth 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 .

When refrigeration first arrived (the 19th century) the equipment was initially used to cool cans of milk, which werefilled 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 harvestingmilk, 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 toremove 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 circulationpump, which flows water across the ice andthe steel walls of the tank, are needed to reduce the incoming milk to a temperature below 5 degrees.
This cooling method worked well for smaller dairies, however was fairly inefficient and wasunable to meet the increasingly higher cooling demand of larger milking parlors. In the mid-1950s direct expansion refrigeration was first applied directlyto the bulk milk cooler. This type of cooling utilizes an evaporator built directly into the inner wall of the storagetank 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 gallonof milk production and prefer to drink slightly warm water as opposedto cold ground water. Forthis 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 productionby 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 United States. As a dairyman increases the size of his herd, he mustalso increase the capacity of his milking parlor in order to harvestthe 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 onbulk milk coolers cannot cool in a timely manner. PHE's are typically utilized in this instance to rapidly cool the milk tothe 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 °F (21 °C) . A second (and sometimes third) section of the PHE is added to remove the ...

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