Slide Set 5: Galactopoiesis

Question 1

Define Galactopoiesis

Answer 1

Maintaining of lactation once lactation (lactogenesis) has been established

Question 2

Maintaining milk production requires:

Answer 2

Ø Maintenance of mammary cell # and activity per cell
Ø Galactopoietic hormones
Ø Milk removal
Ø Neither one of these two factors can maintain lactation on its own.

Question 3

What is the hormonal complex needed to maintain galactopoiesis?

Answer 3

Prolactin is the most important
Ø Growth hormone 
Ø Adrenal corticoids 
Ø Thyroid hormones 
Ø Ovarian steroids

Question 4

What is the consequence of hypophysectomy on galactopoiesis?

Answer 4

Galactopoiesis is inhibited

Question 5

How can galactopoiesis be restored after a hypophysectomy?

Answer 5

• Prolactin (Rabbit)
• Prolactin & adrenal steroids (rats)
• Thyroid hormones & growth hormone (sheep & goats)

Question 6

What is the role of prolactin in galactopoiesis?

Answer 6

Ø Galactopoietic
Ø Increase milk yield by increasing protein synthesis, especially casein
Ø Well-established role in monogastric animals
Ø Ambiguous role in ruminants

Question 7

What is the role of glucocorticoids in galactopoiesis?

Answer 7

Ø Galactopoietic
Ø Increase casein biosynthesis
Ø Increase glucose uptake by the mammary epithelial cells
Ø Inhibitory effect at high doses

Question 8

What is the role of the growth hormone in galactopoiesis?

Answer 8

Ø Galactopoietic
Ø Re-partition of feed energy & amino acids from tissue synthesis to more milk production
Ø Increase glucose and amino acid uptake by the mammary tissue

Question 9

What is Recombinant Bovine Somatotropin (rBST)? What does it do? Is it allowed in Canada? How much is administered?

Answer 9

Ø Galactopoietic
Ø Significant increase in milk production (10-20%)
Ø Improve feed efficiency
Ø Some concerns about cow health
Ø Not allowed in Canada
Ø About 25% of dairy farms in USA use rBST
Ø Commercial rBST co-ordinates changes in metabolic tissue
Ø Produced by MONSANTO
Ø Approved by FDA in 1993
Ø Administered at a dose of 500 mg/cow every 2 weeks Ø Given for at least 60 days postpartum
Ø Average increase in milk 10-15%

Question 10

What are the effects of rBST on body tissues?

Answer 10

• Decreased uptake of glucose

- Decreased oxidation of AA for energy

Question 11

What are the effects of rBST on liver?

Answer 11

• increases gluconeogenesis

Question 12

What are the effects of rBST on fat stores?

Answer 12

• Decreased uptake of glucose and acetate
• Decreased lipogenesis during +ve energy balance
• Increased lipolysis during –ve energy balance
• Increased glucose from glycerol via lipolysis

Question 13

What are the effects of rBST on mammary gland?

Answer 13

Increased:

• Blood flow
• Milk synthesis Glucose uptake & lactose synthesis NEFA utilization for milk fatty acid synthesis
• Amino acid utilization for protein synthesis
• Maintenance of secretory cell #

Question 14

What is the role of insulin in galactopoiesis?

Answer 14

Ø Galactopoietic in non-ruminants
Ø Maintains mammary cell # and some enzymes
Ø Increase uptake of glucose and some amino acids by the mammary gland

Question 15

What is the role of milk removal in galactopoiesis?

Answer 15

• suckling + milking –> galactopoietic hormones –> galactopoiesis
• Acute accumulation of milk in the mammary gland –> increased intra-mammary pressure –> Activation of sympathetic nerves in mammary gland –> Low mammary blood & hormonal flow –> No further milk production or secretion
• Acute accumulation of milk in the mammary gland –> Accumulation of Feedback Inhibitor of Lactation (FIL) –> No further milk production or secretion

Question 16

Maintaining of lactation is a two-component process:

Answer 16

Galactopoiesis = Galactopoietic hormones + milk removal

Question 17

Hormonal vs Local control of galactopoiesis

Answer 17

• Shortly after milking: milk secretion under systemic control
• As milk accumulates: Influence of local control increases

Question 18

Milk removal stimulates milk secretion by 3 mechanisms:

Answer 18

1- Frequent suckling promotes the regular synthesis and release of both prolactin (milk synthesis) and oxytocin (milk ejection)
2- The amount of suckling is closely related to the amount previously removed (i.e. demand)
3- The reduced milk production is caused by the diminished stimulation of the mammary gland by prolactin and the by increased intra-mammary pressure resulting from distention of the mammary ducts and alveoli with stored milk

Question 19

What does VIP stand for?

Answer 19

Vasoactive Intestinal Peptide

Question 20

What does PIF stand for?

Answer 20

Prolactin Inhibiting Factor

Question 21

How does posterior pituitary affect milking?

Answer 21

Secreted oxytocin –> milk ejection

Question 22

How does anterior pituitary affect milking?

Answer 22

Secreted prolactin –> milk production

Question 23

How long should women breast feed? According to AMA and WHO?

Answer 23

• American Academy of Pediatrics
– Six month exclusive
– One year with supplemental food

• WHO
– Six month exclusive
– Two years(or more) with supplemental food

Question 24

What is Lactation amenorrhea (LM)?

Answer 24

• Temporary suppression of female fertility as a result of breast feeding (early months after delivery)
• A more common process in countries where contraceptives are not common and breast feeding is high

Question 25

What is the mechanism of lactation amenorrhea?

Answer 25

Possible mechanism: high prolactin concentration inhibit gonadotropin releasing hormone. β-endorphin is also involved
inhibiting ovulation

Question 26

What are the conditions of LAM?

Answer 26

1. Menses returned? NO
2. Supplementing breastfeeds regularly? NO
3. Baby older than 6 months? NO
   Then 1-2% chance of pregnancy

Question 27

What is galactorrhea?

Answer 27

• Spontaneous secretion of milk from the breast under non-physiological conditions
• Small amount of milk or viscous fluid is expressed for weeks or years in females who have previously been pregnant or lactating

Question 28

How is galactorrhea triggered?

Answer 28

• Can be triggered by thryotoxicosis and some drugs (phenothiazines)

Question 29

Why does galactorrhea occur?

Answer 29

• 30% of women with galactorrhea have higher than normal prolactin levels (healthy women)
• Some women have problems (hyperprolcatinemia, amenorrhea, lack of libido)