Lactation

What are the two primary functions of mammary glands?

To provide nutrition and passive immunity to offspring.

What is colostrum?

The first milk produced that provides passive immunity to babies via immunoglobulins.

What are the characteristics that define mammals?

Most have hair and all have mammary glands, which are modified sweat glands.

What is lactation?

A critical reproductive strategy in mammals involving milk secretion.

Describe the structure of a cow's udder.

It has 4 glands that terminate in 4 teats.

Structure of a mares udder

4 glands served by 2 teats

Structure of a sheep's udder

2 glands and two teats

How many glands and teats do sows have?

6-20 glands, with about 10-14 functional teats.

What type of gland is a mammary gland?

An exocrine gland that secretes milk into a duct.

What is lactoferrin?

An antimicrobial protein that binds to iron, inhibiting bacterial growth.

Lysozyme

Enzyme that hydrolyzes bacterial cell walls.

What is the primary composition of milk?

88% water, with lactose, fat, protein, minerals, and vitamins making up the remaining 12%.

What is fore-milk?

The first drawn milk that is lower in fat compared to later milk.

Fat content ——— after each milking

Increases

What is mastitis?

An infection or inflammation of the mammary gland, the most costly disease in dairy cattle.

What are the main causes of mastitis?

Dirty milking equipment, poor milking practices, and injuries to cows.

What is the ideal dry period for dairy cows?

2 months before the next calving.

How long does the calf have to consume colostrum

24 hours

What is the lactation curve?

The pattern of milk production that increases initially, peaks, and then decreases.

What hormones are responsible for initiating lactation?

Growth hormone (somatotropin), adrenal corticosteroids, and prolactin.

What is the role of oxytocin in lactation?

It causes contraction of myoepithelial cells to eject milk from the alveoli.

What is the significance of the median suspensory ligament?

It separates the left and right halves of the udder.

Mammorgensis

structural development or growth of mammary gland

Lactogenesis

associated with the end of pregnancy and parturition; tissues change from nonlactating to lactating state

Circulatory system role in lactation

extremely important for mammary function. ~500 gallons of blood pass through the udder to produce one gallon of milk

Estrogen role in lactation

Duct and cistern growth

Progesterone role in lactation

Stimulate growth of alveoli

How long until milk let down occurs

45 sec

Negative pressure

allows streak canal to open via vacuum (milking machine)

Positive pressure

allows streak canal to open via squeezing (hand milking)

Oxytocin

produced from the posterior pituitary gland and causes contraction of myoepithelial cells surrounding each alveolus

Epinephrine (Adrenalin) effect on lactation

if released into blood and can override action of oxytocin (reduces blood circulation to alveoli and blood is redirected to muscle for flight response)

Dry period in dairy

2 months

Wet period in dairy

305 days (10 months)

What is galactopoiesis?

The maintenance of lactation.

What is the role of the neuroendocrine reflex in lactation?

Teat stimulation triggers the hypothalamus to signal oxytocin release for milk letdown.

What factors influence milk composition during lactation?

Stage of lactation, season, and the cow's age.

Persistency of lactation

measured how milk production is maintained over time. Production of current month as a percentage of last month (90-92%)

Lactation curve

increases first few weeks and peaks ~4-6 weeks then decreases

What happens to milk production if milking is stopped?

Alveoli become distended, secretory tissue involutes, and milk production stops.

What is the transition period in dairy cows?

The period of 3-5 days when the cow transitions from producing colostrum to normal milk.

What is the impact of stress on milk letdown?

Stress can inhibit milk letdown by releasing epinephrine, which overrides oxytocin's effects.

What is the typical gestation period for dairy cows?

Approximately 280 days.

What is the significance of proper feed and management in dairy cows?

They are crucial for reaching the genetic potential for milk production.

What is the role of myoepithelial cells?

They surround epithelial cells in alveoli and are involved in milk ejection.

What is the streak canal?

The bottom opening of the teat that allows for milk removal.

How does the structure of teats facilitate milking?

Teats are hollow tubes with valves that open and close to allow milk flow.

What is the relationship between calf vigor and milk production?

Male offspring typically cause greater milk production than females.

Dairy cow reproduction lactation cycle

bred to calve at ~2 and gestation is ~280 days. Lactation begins and calving then milking machine is used next 305 days and then dried for 45-60 days prior to next calving then bred back at 90 days of lactation (concurrently lactating and pregnant)

Swine reproduction and lactation cycle

gestation 144 days, piglets left to suckle; wean at ~21 days. Lactational anestrous (lactation inhibits normal cycling). Next estrus occurs several days after removing piglets

Prolactin

produced by the pituitary gland, primarily known for stimulating breast development and milk production