Skip common site navigation and headers
United States Environmental Protection Agency
Ag 101
Begin Hierarchical Links EPA Home > Ag Center > Ag 101 > Dairy Production > Lifecycle Production Phases End Hierarchical Links


Lifecycle Production Phases

Typical LIfe Cycle of a Cow
A cow typically remains in the dairy herd til about 5 years of age, although many cows are capable of remaining productive in the herd for 12 to 15 years. Following birth, the calf is usually removed from her dam after only a few hours. The newborn calf is fed milk or milk replacer until weaning at 6 to 8 weeks of age. The calf will then be raised until it reaches appropriate breeding weight at about 15 months of age. Heifers are then maintained and continue to grow through their gestation. They usually calve, or give birth, at about 24 months of age. However, they do not reach mature size until at least 4 years of age.

Newborn Calf
Normally cows begin to produce milk only after calving, but some heifers may be milked early to reduce stress and udder edema. Each period of production or lactation lasts for 12 to 14 months or longer and spans the time period from calving to dry-off, which is when milking is terminated about 60 days before the next anticipated calving. Thus, cows are bred while they are producing milk, usually beginning at about 60 days after calving to maintain a yearly calving schedule. Indeed, dairy producers attempt to get cows bred precisely during the time they are producing the most milk, which has negative implications for cow fertility. Following the 2-month dry period, the cow calves again and lactation cycle begins anew. Cows average about 2.5 lactations, although many remain productive considerably longer. Cows tend to survive longer in less-intensive pasture systems than when on concrete all of the time. The leading reasons cows leave the dairy herd are low production, infertility, mastitis (inflammation of the udder), and lameness.

Back ArrowBack to Dairy Main Menu

Calves and Heifers

Valves are fed colostrum immediately after birth.
(Source: University of Wisconsin)
Immediately after birth, the calf is fed 2 quarts of colostrum and at least another 2 quarts within 12 hours. The ability of the calf to directly absorb immunoglobulins from the cow's initial milk declines rapidly after the first 12 hours. Thus every effort is made to get the calf to consume colostrum early. Calves' navels are then dipped with iodine to prevent infection and the calf is moved to an individual pen or hutch as soon as it is dry. Choices for individual housing for calves include calf hutches, indoor crates, and indoor pens. Group pens allow too much nose-to-nose contact and permit disease to spread quickly for very young calves. Hutches provide very suitable ventilation for the calves and automated equipment can be used to simplify feeding calves in hutches. But indoor facilities are convenient for the calf feeders, especially in cold weather. Often indoor calf facilities are made of converted buildings, greenhouse barns, or coverall hoop barns.

Prior to weaning at 6 to 8 weeks, calves are vaccinated, dehorned, have extra teats removed, and male calves may be castrated to be raised as steers. Female calves are either raised by the dairy farm as replacement heifers, contract raised for the dairy farm by a heifer grower, or sold to other dairy farms. Male calves are mainly sold as veal calves or raised as steers, either by the farm or a buyer. A small number of bull calves may be raised for breeding stock and sold to local dairies as natural service bulls. A tiny percentage of bull calves from exceptionally good cows with registered pedigrees may be sold through contract to Artificial Insemination companies. Formerly, the image of the veal industry is that calves were kept in tiny crates in total darkness so they would remain anemic. The modern veal industry is more likely to be in more open facilities with excellent lighting and ventilation.

Protein Sources
Best Acceptable Inferior
Skim Milk Specially manufactured soy flour Unprocessed soy flour
Buttermilk Soy concentrate Meat solubles
Whole Whey Hydrolyzed fish protein Fish Flour
Delactosed whey   Distiller solubles
Casein   Brewer's yeast
Milk albumin   Oat flour
Whey protein concentrate   Wheat flour
Fat Sources
Lard Hydrogenated vegetable oils Liquid vegetable oils
Stabilized greases    

Aside from the very first days when calves are fed colostrum, they are fed discarded milk or milk replacer. The best protein sources for milk replacer are from dairy products. At the same time, the calf is offered water and calf starter feed, which it should be consuming readily prior to weaning it off of milk. Calves should be offered starter within the first week and should be getting adequate energy from the starter by weaning. Often calves are encouraged to eat the starter by addition of molasses. It is not necessary to feed hay to calves prior to weaning, but it is sometimes made available.

Protein Sources
  Grain Starters
1 2 3
Ingredients (air dry basis)  
Corn (cracked or coarse ground), % 50 30  
Ear Corn (coarse ground), %     50
Oats (rolled or crushed), % 22 18  
Barley (rolled or coarse ground), %   20 21
Wheat Bran, %   8  
Soybean Meal, % 20 16 21
Molasses, % 5 5 5
Dicalcium phosphate, % 0.5 0.5 0.5
Limestone, % 1.5 1.5 1.5
TM Salt and Vitamins, % 1 1 1
Composition (dry matter basis)  
Crude protein, % 18.1 18.0 18.4
TDN, % 80.0 78.8 78.0
ADF, % 7.0 6.9 9.1
Calcium, % 0.8 0.8 0.82
Phosphorus, % 0.48 0.56 0.47
Vitamin A, IU/lb 1000 1000 1000
Vitamin D, IU/lb 150 150 150
Vitamin E, IU/lb 11 11 11

At weaning, calves are moved to group housing. Forms of group housing include superhutches, drive-through freestall barns, drive-by freestall barns, and open housing on bedded pack. Some calves are weaned directly onto pasture. Normally, heifers are kept in these housing systems until they reach breeding age at 12 to 15 months. Feeds tend to include some calf starter, perhaps some other grain or corn silage; and excellent quality hay is offered.

Following breeding, heifers are maintained until moving to the dairy farm for calving. Facilities are often less extensive. Often heifers are raised in feedlots, or on pasture, although some heifers are also raised in freestall barns.

Back to Top


Maternity PensFor cows, the period from 60 days prior to calving until 40 days after calving is called the transition period, because cows make a transition to producing milk and consuming a higher energy ration. Heifers and dry cows are usually moved to a close-up dry area for close observation beginning at 3 weeks prior to calving. Usually the close-up dry cows are housed in freestalls, or on pasture or open lot. When calving appears imminent, cows are moved to individual maternity pens or an open calving area. Diligent efforts are made to keep these areas clean. Even cows raised on pasture are sometimes moved to pens for calving to allow close observation in case the delivery must be assisted, to keep the calf out of cold drafts, and to allow careful attention to the calf immediately after birth. Calving pens are usually bedded with lots of clean wheat or oat straw, although sand and sawdust are used too.

Some dairy producers prefer to keep cows on pasture. There are certainly advantages in reduced costs of feed harvest and storage, reduced cost for manure management and storage, improved foot health, and perhaps less disease when the cows are not as heavily concentrated in a limited area. These grazing systems often depend on the principles of managed intensive grazing to optimize grass and milk production. Some, but not all, grazers also practice seasonal calving to allow the cow's highest milk yield and energy demands to match with seasons of maximal grass production. Thus calving is planned for Spring in the Northeast and Midwest, and Fall in the far South. Due to less rainfall, little grazing is practiced west of the Great Plains. Grass is far and away the key component of diets on grazing dairies. Even stored feed may include excess grass from pastures that is ensiled and fed when grass is not available. Most grazing dairies supplement the grass with some level of ground corn or other concentrate feeds, and perhaps with some purchased alfalfa hay and/or corn silage. Often the grass is baled in round bales, wrapped in plastic, and stored as baleage.

Tie Stall Barn for CowsIn the Midwest and elsewhere it is common for small to medium-sized dairies to house cows in barns for most of the year, but to provide supplemental grazing during the summer. Even then, cows may only get a small portion of their forage from pasture, with most feed fed in the barn or a feedlot.

Traditionally, cows in the Midwest and Northeast were housed in tie-stall barns. Often cows were maintained in these barns and fed and milked right in their own stalls. While several of these barns are still in use, the inefficiency of labor and difficulty of milking have made new tie stall barns relatively uncommon.

The concept of providing cows with the opportunity to freely move from her stall to the feeding area was developed in Washington State in the mid 1950s. Freestall barns have become the mainstay of the dairy industry in recent years. Older freestalls were often constructed of wood and the stall was bedded with lots of straw. Even these older stalls can still be very useful today if plenty of bedding is provided to keep cows comfortable. Freestall Barn for Cows Modern freestalls are more likely to be constructed of steel loops or dividers and bedded with sawdust or sand. The fact that sand provides little organic matter as food for bacteria, keeps cows dry, and helps cool cows in summer makes it the "gold standard" of bedding materials. Occasionally, freestalls are lined with rubber mattresses filled with ground tires, other cushion materials, or even water. Modern barns are constructed of wood or steel supports and rafters or trusses, steel roofing with an open ridge, and curtain sides that may be opened to maximize airflow in summer. Ventilation is usually assisted with fans. In some facilities, tunnel ventilation is used, in which air is mechanically drawn through the length of the building at rapid speed, which eliminates the dependence on wind speed needed for natural ventilation. To attain rapid air movement, the roof and sides are built solid with no air inlets. Greenhouse barns and other kinds of hoop structures are available to dairy producers for freestall barns. Their advantage is in reduced construction costs, although covering may need to be replaced as often as every 5 years. The additional light in these barns is an advantage for observing cattle, and the sun may be partially blocked out by covering with shade cloth in summer. Cow cooling systems, such as misters or sprinklers, are often present above feeding areas during hot weather. In the arid Southwestern states, newer dairy facilities are investing in state-of the art evaporative cooling systems to keep cows comfortable and productive. Supplemental cow cooling should be available any time the temperature exceeds 72 to 75 degrees.

Dry cows, during the period in which they are not lactating, are often housed in less expensive buildings. Because dry cows do not metabolize as much energy as lactating cows, they produce less heat, and so it is not as difficult to keep them cool in summer.

Back to Top

Back ArrowBack to Dairy Main Menu


Begin Site Footer

EPA Home | Privacy and Security Notice | Contact Us