Dairy cows have a life expectancy of approximately 6 years, which is less than that of other domestic cows. The life cycle of a dairy cow has various stages from the birth of a wobbly legged calf, to a heifer and finally a mature cow. Dairy cows only begin to produce milk after calving and can yield an average of 27 litres per day. As such, in order for farmers to acquire maximum production, there is need to have sound understanding of the dairy cow life cycle. This aids in proper livestock management which is essential for the health and productivity of dairy cows, hence a lucrative dairy farming venture.
The life cycle of a dairy cow begins at birth. When a calf is born, the placenta is removed and the cow is allowed to lick it dry. Some calves are born weak, others with bone deformities due to poor nutrition among pregnant cows and stress from birth complications. Such calves require special care as they are most likely to die within the first 3 days. During this period, new born calves are highly susceptible to disease and infection. This is because calves are born with an extremely poor immune system. If proper care is not taken, the mortality rate can be very high. It is recommended to provide calves with good quality colostrum within 5 to 6 hours of birth as it promotes immunity, hence the ability to fight prevalent diseases and infections. Colostrum can be fed directly to new born calves or cooled rapidly to 4oC for short term storage. The survival of calves at this stage can depend on colostrum. For this reason, they must be allowed to suckle from the mother for the first couple of days. Some farmers prefer to separate the calf from the mother after a few hours of life to ensure that they do not get too attached. It is during this period of the dairy cow life cycle that its future is determined, provided it is male. The calf can be castrated and raised as a steer, kept entire and used for future breeding or used for as a source of semen for artificial insemination programmes. Calves preferred for breeding must be healthy and well-bred; pure breed are often selected for artificial insemination. A female calf can either be raised as a replacement dairy cow or for sale when it reaches the desirable age and weight.
Post Birth Period to Weaning
This is the period after birth in a dairy cow life cycle. It begins soon after a calf is separated from the mother which is usually 2 to 3 days old until it is about 6 to 8 weeks of age. After separation, the calf is introduced to calf starter but diet is still dependent on liquid nutrition. Note that if it is fed a lot of milk for prolonged periods of time it might not develop a strong appetite for dry feed which affects stomach development and growth. For this reason, the calf starter is replaced on a daily basis. It is fed calf starter, a grain, beginning at 7 to 10 days of age. After about 3 to 4 weeks, calves start developing increased appetites hence their feed intake should be adjusted accordingly. By the time calves reach weaning age which is about 4 to 8 weeks old, they should be consuming higher amounts of calf starter. Calf starter intake may even double. Once reaching 12 weeks, a calf grower feed is introduced. Grower feeds can help calves transition more easily to a high fibre diet. During the weaning stage calves should gain about 800g per day and prior to that about 600g a day. Following weaning, calves can be vaccinated against certain bacterial or viral diseases and be given treatment for parasites.
The stage that comes after weaning in the life cycle of a dairy cow is breeding. After the weaning period, calves live in group pens of 4. They are then amalgamated to groups of 16 that are further expanded after another 4 weeks. Cows are raised in these group pens until they reach the appropriate age for breeding which is usually 15 to 18 months depending on the weight of the heifer. In fact, heifers should enter the milking herd with a weight equal to or greater than 85% of mature body weight. The target breeding weight of heifers is somewhat between 350 to 375kg. Cows raised on pasture have a target breeding weight that is slightly lower, approximately 310 to 350kg. Breeding relies on weight rather than age and so heifers that weigh less are given additional time to grow; those that reach the target weight earlier are put into calving sooner. Therefore, once reaching the ideal weight, the heifer is mated with a bull in order to facilitate pregnancy and consequently start producing milk. A female cow must calve once a year in order to maintain maximum milk production. After calving, the heifer is known as a cow.
After gaining the ideal weight for breeding, the next stage in the life cycle of a cow is gestation. Most farmers favour artificial insemination over natural means as it provides them with the ability to choose different sires for different cows, or the sex of the calf. A teaser bull maybe used to determine if the cow is coming into heat; this can also be done through the use of various devices such as tail paint, pedometers and Kamar dictators. During the pregnancy phase of a dairy cow life cycle, a heifer is kept in the rearing group. A heifer that is put into breeding at 15 months of age must calf at about 24 month which is approximately 9 months or 283 days. Milk production begins at this stage in order to provide the necessary colostrum for health development of new born calves. The calf is separated from the mother so as to acquire increased milk yield. The calf basically goes through the previously mentioned stages which include post-birth to weaning, breeding and finally gestation, and the continuation of the full dairy cow life cycle. Note that cows at this stage are not fully mature. Therefore through this period they continue to grow and develop; cows do not reach full maturity until about 4 years old. The lactation period can last for approximately 12 months but milk production declines around 10 months. The cow is milked throughout the lactation period and also mated with a bull. In addition, a cow must be put into a dry period 7 months after mating and about 60 days before calving the second time. Lactation period should then come to a halt whereby the cow is no longer milked. Note that after the delivery of a calf, the lactation period begins again and the whole life cycle of a dairy cow is repeated.