Dairy Cattle Lactation (Part 1)

Question 1

Lactation

Answer 1

The production of milk by the mammary gland

Question 2

Mammogenesis

Answer 2

Growth and development of the mammary gland

Question 3

Galactopoiesis

Answer 3

Maintenance of lactation

Question 4

Involution

Answer 4

Cessation of milking

Question 5

Mammogenesis
Zygote → First calving

Answer 5

Only once during development

Positive growth

Question 6

Mammogenesis
Conception → Drying off

Answer 6

Part of normal reproductive cycle

Positive and negative growth (involution)

Question 7

Most critical stage in Mammogenesis

Answer 7

Prepubertal

Question 8

Most growth stage in Mammogenesis

Answer 8

Pregnancy

Question 9

Mammogenic hormones

Answer 9

E2 , P4, GH , adrenocorticoids , PRL , Lactogen ,insulin,IGFs , Thyroid

Question 10

Allometric mammary Growth Rate

Answer 10

Faster than the rest of the body

starts at 3-4 months of age and continues after puberty through the first few estrous cycles (until about 1 year of age)

Question 11

Isometric Mammary Growth Rate

Answer 11

Similar to the rest of the body

After 1 year of age to conception

Question 12

Over feeding during the allometric phase (especially before puberty) can result in …

Answer 12

excess fat deposition & inhibition of parenchymal growth and future milk production

Question 13

Mammary tissue in heifers fed ad libitum was …

Answer 13

> 80% fat

Question 14

Heifers fed a restricted diet have around …

Answer 14

65% fat , and 13% more parenchymal Tissue compared & with heifers ad libitum

Question 15

Overfeeding during the prepubertal period …

Answer 15

reduces GH levels

Question 16

GH effect with mammary growth

Answer 16

GH has a positive correlation with prepubertal mammary growth

Question 17

Mammary development
30 to 40 days of bovine fetus

Answer 17

Initial development

Question 18

Mammary development
At birth

Answer 18

1. Externally teats are present
2. Internally, teat cistern + gland cistern + little CT + little fat

Question 19

Mammary development
Until 1st pregnancy (prepubtal)

Answer 19

↑ CT + ↑ fat + ↑ ducts + Slow growth and development of the teats and duct system

Question 20

Mammary development
At puberty

Answer 20

E2 stimulates growth and development of the ducts

Question 21

Mammary development
Puberty to conception

Answer 21

elongation and branching of the ducts + stromal growth (especially blood vessels)

Question 22

Most of the mammary growth … occurs during pregnancy

Answer 22

45-90%

Question 23

Mammary development
Early pregnancy

Answer 23

ductal growth

Question 24

Mammary development
Mid to late pregnancy

Answer 24

Alveolar development

Question 25

Mammary development
Last month of pregnancy

Answer 25

Colostrum secretion

Question 26

Ducts differentiate into

Answer 26

milk secretory cells (lobule-alveolar system)

The duct network occurred until puberty will determine the extent of lobule-alveolar development during gestation

Question 27

Mammary development
Early lactation

Answer 27

Number of milk secreting cells reaches a maximum at Peak lactation (40-70 d), then
declines towards the end of lactation

Question 28

Lactogenesis

Answer 28

A process of differentiation by which the mammary alveolar cells acquire the ability to secrete milk (Milk contents) i.e. convert & from a now-secretory state to a secretory state

Question 29

Lactogenesis I

Answer 29

associated with limited secretion (colostrum secretion)

Question 30

Lactogenesis II

Answer 30

Associated with copious milk secretion shortly before parturition and postpartum