Slide Set 5: Galactopoiesis Flashcards
Define Galactopoiesis
Maintaining of lactation once lactation (lactogenesis) has been established
Maintaining milk production requires:
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.
What is the hormonal complex needed to maintain galactopoiesis?
Prolactin is the most important Ø Growth hormone Ø Adrenal corticoids Ø Thyroid hormones Ø Ovarian steroids
What is the consequence of hypophysectomy on galactopoiesis?
Galactopoiesis is inhibited
How can galactopoiesis be restored after a hypophysectomy?
- Prolactin (Rabbit)
- Prolactin & adrenal steroids (rats)
- Thyroid hormones & growth hormone (sheep & goats)
What is the role of prolactin in galactopoiesis?
Ø Galactopoietic
Ø Increase milk yield by increasing protein synthesis, especially casein
Ø Well-established role in monogastric animals
Ø Ambiguous role in ruminants
What is the role of glucocorticoids in galactopoiesis?
Ø Galactopoietic
Ø Increase casein biosynthesis
Ø Increase glucose uptake by the mammary epithelial cells
Ø Inhibitory effect at high doses
What is the role of the growth hormone in galactopoiesis?
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
What is Recombinant Bovine Somatotropin (rBST)? What does it do? Is it allowed in Canada? How much is administered?
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%
What are the effects of rBST on body tissues?
- Decreased uptake of glucose
- Decreased oxidation of AA for energy
What are the effects of rBST on liver?
- increases gluconeogenesis
What are the effects of rBST on fat stores?
- Decreased uptake of glucose and acetate
- Decreased lipogenesis during +ve energy balance
- Increased lipolysis during –ve energy balance
- Increased glucose from glycerol via lipolysis
What are the effects of rBST on mammary gland?
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 #
What is the role of insulin in galactopoiesis?
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
What is the role of milk removal in galactopoiesis?
- 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
Maintaining of lactation is a two-component process:
Galactopoiesis = Galactopoietic hormones + milk removal
Hormonal vs Local control of galactopoiesis
- Shortly after milking: milk secretion under systemic control
- As milk accumulates: Influence of local control increases
Milk removal stimulates milk secretion by 3 mechanisms:
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
What does VIP stand for?
Vasoactive Intestinal Peptide
What does PIF stand for?
Prolactin Inhibiting Factor
How does posterior pituitary affect milking?
Secreted oxytocin –> milk ejection
How does anterior pituitary affect milking?
Secreted prolactin –> milk production
How long should women breast feed? According to AMA and WHO?
• American Academy of Pediatrics
– Six month exclusive
– One year with supplemental food
• WHO
– Six month exclusive
– Two years(or more) with supplemental food
What is Lactation amenorrhea (LM)?
- 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
What is the mechanism of lactation amenorrhea?
Possible mechanism: high prolactin concentration inhibit gonadotropin releasing hormone. β-endorphin is also involved
inhibiting ovulation
What are the conditions of LAM?
- Menses returned? NO
- Supplementing breastfeeds regularly? NO
- Baby older than 6 months? NO
Then 1-2% chance of pregnancy
What is galactorrhea?
- 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
How is galactorrhea triggered?
- Can be triggered by thryotoxicosis and some drugs (phenothiazines)
Why does galactorrhea occur?
- 30% of women with galactorrhea have higher than normal prolactin levels (healthy women)
- Some women have problems (hyperprolcatinemia, amenorrhea, lack of libido)
