Similar to humans, cows need to be pregnant and give birth to milk production and release to occur. Milk production involves the complex interaction of several different hormones, which are set into play during pregnancy. Dairy Herds are in a constant Cycle of Pregnancy and Milking. A Lactating Cow can Produce 90 Glasses of Milk a day
What is a Heifer?
A female calf of one year of age. At what age is it safe to breed a heifer?
Breeding should occur when the heifer reaches puberty. Puberty is a function of the breed, age, and weight. Most heifers will reach puberty and be bred by 12 to 14 months of age and will be between 55% and 65% of their mature weight when they first begin to exhibit estrous cycles.
Higher growth heifers and heifers that have a breed composition that is a high percentage of Bos indicus are later maturing and are older at puberty.
There are, in some cases, beef females that will cycle at less than a year of age and become pregnant. This is called precious puberty. This female may be still nursing their dams. This doesn’t happen often but can happen. This is too young for a beef female to become pregnant because, at calving, these females tend to have difficult births as the birth canal is not fully developed.
The Lactating Cycle of Cow:
After calving, every cow or heifer goes through the lactating cycle.
Understanding the lactation:
The cycle is split into phases; the early, mid-lactation, late lactation, and dry period. In an ideal world, cows calve every twelve months, as they must calve to be able to produce milk.
A dairy cow is a mammal. Mammals are animals that have hair, are warm-blooded, and nourish their young with milk. The mammary gland of a cow is a fascinating structure. Mammary glands develop before birth and further develop and grow when the cow is pregnant.
We commonly refer to the mammary glands of a cow as the udder. These skin glands are located on the underside of the cow, between the rear legs. The four glands are referred to as quarters.
Several factors play a role in determining how much milk a cow will give such as age, breed, genetics, and the environment.
A cow should spend 10 to 14 hours a day lying in the stall, resting, and making milk. Moderate exercise is important to maintain high milk production.
- Mature cows produce about 25% more milk then two-year-olds.
- Milk production increases until about eight years of age.
- Holstein is the most prominent breed of dairy cattle producing around 23,000 pounds of milk a year.
Approximately 400 to 500 gallons of blood pass through the udder for each gallon of milk production. One of the roles of the mammary gland is to take nutrients from the cow’s blood and synthesize them into milk that is then secreted into the mammary glands. At the end of pregnancy, these glands undergo a process that initiates milk secretion.
The production of milk requires that a cow is in lactation, which is the result of giving birth. Gestation is around 279 days when the majority of mammary development occurs.
The actual lactation begins at calving. It doesn’t only involve the production of milk, but also the development and function of the mammary gland, the metabolic and reproductive status of the cow, and the development of the calf.
Hormones and removal of milk from the udder are the two key components that contribute to the maintenance of lactation.
Therefore, lactation is the result of having a successful reproductive program.
Colostrums is the first milk produced by the cow after calving. The composition of colostrums is different from that of normal milk as it contains a higher concentration of antibiotics.
The Function of the Udder:
Milk is a major source of nutrition and is composed of
- and vitamins.
Milk is produced by cells grouped as hollow spheres and tiny storage units called alveoli. They appear as sac-like structures and lined with epithelial cells. Epithelial cells are secretory cells that produce milk during lactation.
Within each mammary gland are millions of alveoli. Since there are many alveoli, all the milk that has been secreted from the cells into the alveoli empty into ducts and subsequent larger ducts which further lead to the gland cistern.
Different Parts of Teat:
There are different parts of the teat. These parts are the orifice, the streak canal, and the cistern.
The orifice is the opening to the papillary duct; normally held closed by the sphincter muscle in the wall of the teat and elastic tissue around the orifice is the primary route in most cases of mastitis.
The Streak Canal:
The streak canal is located at the end of each teat. The canal is ¼ to ½ inch in length and is made up of extensions of the skin that lie close together. The streak canal is held closed by sphincter muscles. The streak canal prevents
- the escape of milk between milking
- acts as a barrier to the entry of bacteria.
The Teat Cistern:
The teat cistern is the final storage area of milk before the cow is milked. The gland cistern joins to the teat cistern at the base of the udder. It is located just above the teat cistern and acts as a milk reservoir.
The gland cistern is the largest storage area for milk as it collects milk from the major milk ducts that flow into it and fills rapidly during milk letdown. The teat cistern is the cavity inside the teat that holds ½ to 1.5 ounces of milk. The teat cistern is where milk accumulates before it is removed through the teat end during milking. It refills continuously during milking.
The internal milk production process, epithelial cells start to replenish the milk supply immediately at the end of milking. The reduced udder pressure increases the blood flow allowing for a high rate of production. The hormone prolactin is present to stimulate the epithelial cells.
The Supramammary Lymph Glands:
The supramammary lymph glands or nodes act as filters that destroy and remove bacteria from the udder. The streak canal is the main barrier against intramammary infection. It is kept closed by a ring-shaped muscle at the lower end of the cow’s teat called the sphincter.
When a cow is milked, this causes the sphincter muscles to relax, opening the orifice. The streak canal remains open an hour after milking, so it is important to help prevent bacteria from teat end contamination.
The cells that line the streak canal contain keratin. Keratin is a waxy substance that helps to seal the teat end between milking and inhibits the growth of bacteria.
The Furstenburg’s Rosette:
The Furstenberg’s rosette is located directly above the streak canal. It is made up of loose folds of membranes that smooth out as milk accumulates in the udder. This aids in blocking the escape of milk between milking.
Median Suspensory Ligaments:
The most important support for the udder is the median suspensory ligament. The median suspensory ligament is located at the center of the udder providing a balanced suspension. It divides the udder into the left and right halves. This major ligament can stretch as the gland fills with milk.
Subcutaneous Mammary Vein:
Subcutaneous mammary vein, also known as milk veins emerge at the front of the udder and run the body at the milk wells. The swelling of the udder is known as edema and is common at calving because a cow’s udder has poor blood circulation.
Only one teat drains one gland of the dairy cow. Almost 50% of calves are born with extra teats, often called supernumerary teats. Extra teats need to be removed before an animal reaches one year old. Many recommend removing extra teats as early as two weeks old. Sometimes cows will have a blind quarter. This is when one of the quarters does not secrete milk.
How to Remove Extra Milk Teats
Often a cow’s lactation cycle is referred to in stages: early lactation, mid-lactation, late lactation, and the dry period. Nutrient requirements will vary with the stage of lactation and gestation.
Your nutrition program can play a critical role in milk production and reproductive performance. Milk production will start suddenly and increase daily in early lactation.
As this happens, a greater amount of nutrients are needed. Mammary tissue function declines after peak lactation, mainly due to the decrease in mammary cell quantity. It is common to group cows according to their stage of lactation in group housing facilities.
Stage 1- Early Lactation from 14 to 100 days: Peak Production
In early lactation, milk production begins at a high rate which continues to increase for three to six weeks after calving. This is known as peak milk production. In the first 100 days, a cow’s feed intake starts to lag, and cows may begin to lose weight because of their rapid milk yield compared to their dry matter intake.
This is called a negative energy balance. Once peak dry matter intake is achieved, the cow will stop losing weight.
Feed intake can be influenced by several factors such as consistency, quality and quantity of feed, and digestibility.
The fresh feed should always be available after milking to encourage consumption. Protein is a critical nutrient during this stage. During this phase, the cow should be bred, typically between 60 to 70 days in milk.
Stage 2-Mid Lactation start from 100 to 200 days:
In mid-lactation, the object is to maintain peak production for as long as possible and maximize dry matter intake. Cows should be eating 4% of their body weight. Feeding high-quality forage is important in mid-lactation. Protein requirements are reduced during mid-lactation.
Stage 3- Late Lactation- 200 to 305 days:
During late lactation, milk production will continue to decline along with feed intake. Cows will gain weight to support the growing fetus and replenish tissue lost from early lactation.
The dry period includes the time between no longer milking the cow and calving. The recommended dry period is 45-60 days. If the dry period is less than 40 days, milk yield will be reduced. The same goes for dry periods over 70 days. A separate feeding program for dry cows is a must.
At 45 to 50 days before calving, you should stop milking the cow. A lot of producers infuse the udder with antibiotics to prevent infections.
Once milking is ceased, and the cow is dried off, involution of the mammary gland takes place. Involution is the process of the return of the uterus to normal function after calving, transforming from a pregnant to a non-pregnant state.
This process is primarily due to the hormone oxytocin. Lactoferrin is a major protein found in mammary secretions during involution and helps with disease resistance. If bred on time, a year after the birth of her first calf, a cow will calve again.
Impacts of Short Lactation Length:
- Poor feeding management of potentially high yielding cows can create many problems.
- Lactation anoestrus can occur as the cows are forced to utilize more of their body reserves in early lactation. This can lead to low peak milk yields and shortened lactation length.
- Cows will dry off prematurely if they receive insufficient feed nutrients to maintain viable processes of milk production in their mammary tissue.
Ideally, cows should be managed to have a two-month dry period to allow the mammary tissue to recuperate before the next lactation.
Cattle Losses 2010
|Cause of Death||Percentage of Total|
World Cattle Breeder Associations
|National Cattleman's Beef Associations||United States||NCBA|
|United States Cattlemans Association||United States||USCA|
|Ohio Cattlemans Association||Ohio||OCA|
|American Angus Association||United States||AAA|
|United Kingdom Cattle Associations||UK||UKCA|
|Australia Cattle Associations||Australia||ACA|