Section 3: Lactation

Question 1

What is involution?

Answer 1

The process of organs drying off. This results in the termination of milk production.

This is te loss of secretary cell activity, resulting in a decline or cessation of milk synthesis. There is a decrease in supply of nutrients to the mammary tissue, and the stimulus of milk removal stops.

Question 2

What is postpartum?

Answer 2

A period in which they do not experience oestrous cycles - temporary infertility cannot be avoided

Question 3

What is the ectoderm?

Answer 3

Outer later, develops into skin and nervous system. It also forms parenchyma for secretary tissue.

Question 4

What is mesoderm?

Answer 4

Middle layer, develops into muscle, vascular system, and sex organs. It also forms stroma for adipose and connective tissue, and blood vessels.

Question 5

What is endoderm?

Answer 5

Inner layer, forms alimentary canal and digestive glands

Question 6

What are factors that affect Mammogenesis and Lactogenesis:

Answer 6

Genotype - amount of tissue

Calving date - age (heifers), body reserves, lactation length

Dry period length – short → lower yield- No dry period, yield decreased between 12 – 20%

Question 7

What occurs in the stage of Birth to Puberty?

Answer 7

• little development of alveoli
• development of stromal (structural) tissue - increasing the growth of the duct system, adipose and connective tissue, ultimately allowing the alveoli to proliferate during lactation.

Question 8

What occurs during the stage of Puberty?

Answer 8

This is the main period of growth between birth and first pregnancy. It is stimulated by onset of ovarian activity.

Question 9

What is oxytocin?

Answer 9

Oxytocin is a hormone released from the posterior pituitary gland, causing a contraction of the myoepithelial cells around alveoli and small ducts of the mammary gland. Thus, oxytocin is generally considered to increase milk production by enhancing milk ejection.

Stress can block oxytocin.

Question 10

What are some regressions of secretory tissues

Answer 10

1. Gradual involution - loss of secretory activity later in lactation
2. Initiated involution - rapid loss of secretory cells following weaning or drying off
3. Senile involution - gradual loss of tissue during old age - feeding the same but they don’t produce much milk.

Question 11

What does it mean by ‘dry period’ in cattle?

Answer 11

It is the end of lactation and the initiation of the next. This is when there is a high turnover of alveolar cells, and rejuvenation of secretory tissue (cattle need 40 to 60 days).

Question 12

Describe how lactation is important for reproductive success

Answer 12

Nutritional Support: Provides essential nutrients and immunity to calves.

Estrus Timing: Influences the return to heat and breeding success.

Body Condition: Ensures energy balance for fertility and regular cycles.

Future Success: Optimizes calving intervals and overall herd health.

Economic Impact: Enhances milk production and breeding efficiency

Question 13

List the reasons why ruminants were domesticated by lactation

Answer 13

Milk production, which provides essential nutrients, supports calf growth, offers economic benefits, and can be processed into various dairy products. Their ability to efficiently convert plant material into milk also supports sustainability.

Question 14

Define Mammogenesis

Answer 14

Development and formation of mammary glands, involving the growth and differentiation of tissues necessary for milk production. Occurs during embryonic development, puberty, pregnancy, and lactation.

Question 15

List the 5 stages of Mammogenesis

Answer 15

Embryonic Development: Initial formation of mammary structures.

Prepubertal Development: Early growth of mammary tissues.

Puberty: Expansion and branching of ducts.

Pregnancy: Preparation of mammary glands for milk production.

Lactation: Maturation and milk secretion

Question 16

Describe the factors that influence Mammogenesis

Answer 16

Hormones: Regulate growth and development of mammary tissues.

Genetics: Determine gland size and structure.

Nutrition: Supports proper gland development.

Age: Affects development at various life stages.

Environmental Factors: Stress and health impact gland function.

Reproductive History: Affects subsequent mammary development.

Question 17

What is the function of the alveoli

Answer 17

Milk production - these small sacs are where milk is synthesised and stored until ejected

Question 18

What is the function of the ducts

Answer 18

To transport milk from the alveoli to the nipple (teat). Milk is collected in larger ducts called lactiferous ducts before being expelled.

Question 18

What is the function of the teat

Answer 18

It is the outlet through which milk is released. Each udder has four teats, each serving a separate quarter of the udder

Question 19

What is the function of the stroma

Answer 19

It provides structural support to the udder. The stroma consists of connective tissue that supports and surrounds the alveoli and ducts

Question 19

What is the function of adipose tissue

Answer 19

It cushions and insulates the udder, contributing to its size and shape and providing energy reserves

Question 19

What is the function of the areola

Answer 19

It is the pigmented area around the teat that aids in calf attachment It has specialised glands that help lubricate the teat

Question 19

What is the function of myoepithelial cells

Answer 19

They surround the alveoli and ducts, and contract to help expel milk during milking and nursing

Question 20

What are the two types of parenchyma tissue? What are their functions?

Answer 20

Secretory and ductal.

Secretory tissue is involved in the production and release of various substances such as milk, hormones, and digestive enzymes.

Ductal tissue refers to the network of ducts or tubes that transport secretions from secretory cells to their target locations. For example, in the mammary glands, ductal tissues transport milk from the secretory cells to the nipple.

Question 21

What is the structure and function of stroma

Answer 21

Consists of the skin, connective tissue, adipose tissue, blood and lymph vessels, and nerve tissue.
Supports organ structure, facilitates function, and helps maintain the integrity of various tissues and organs.

Question 22

Describe the main components of milk and how they are synthesised

Answer 22

water - absorbed from the bloodstream (makes up 87-88% of milk)

fat - primarily triglycerides, synthesised from fatty acids and glycerol (makes up 3.5-4% of milk)

casein - major protein in milk

whey - proteins that is involve in the support of the immune system, and are synthesised during lactation.

lactose - a sugar that is synthesised from glucose and galactose by the enzyme lactase synthase ( makes up 4.5-5% of milk)

ash - mineral content, derived from the diet, contributing to the nutritional value of milk

Question 23

What is casein?

Answer 23

Provides essential amino acids and is a major source of protein in milk.
Casein proteins aggregate into large, complex structures called casein micelles, which are stable and help to keep calcium and phosphate in solution.

Question 24

What are the three main components of milk?

Answer 24

– Lactose synthesis
– Protein synthesis
– Fatty acid synthesis (tryglycerides)

Question 25

What is galactopoietic?

Answer 25

Galactopoietic is the synthesis of milk during an established lactation – Nutrition can impact on galactopoietic

Question 26

What are the three pathways for Glucose-6-phosphate

Answer 26

1. Glycolysis for triglyceride formation and generation of ATP
2. To form galactose for lactose production
3. The pentose phosphate pathway for triglyceride formation