Somatotropin

Question 1

What is lactogenesis and galactopoiesis?

Answer 1

Lactogenesis = start of milk production
Galactopoiesis = maintenance of milk production

Question 2

Describe the hormonal stimulation of lactogenesis

Answer 2

• Towards end of gestation P4 levels decline and E2 levels rise
• E2 stimulates prolactin release from anterior pit gland and increased number of prolactin receptors on mammary cells
• surge in prolactin in hours before parturition
• glucocorticoids (e.g., cortisol) levels rise prior to, and during parturition
• cortisol binds to receptors on mammary cells and induces increase in RER
• this allows increase secretion of a-lactalbumin and B-casein (major components of milk)

Question 3

Describe the hormonal control of galactopoiesis

Answer 3

• thyroid hormones ensure mammary gland is high priority for nutrient delivery by reduced conversion of T4 to T3 in liver and kidney but increasing it in mammary tissue
• suckling induces increase in prolactin release
• removal of milk from udder is necessary for continuation of galactopoiesis
• GH partitions additional nutrients to mammary cells to increase synthesis of milk protein, lactose and milk fat
• GH antagonises action of insulin to inhibit lipogenesis and stimulate HSL to mobilise FA stores to be converted into milk fat

Question 4

What happens to milk production if milk is not removed from the udder?

Answer 4

reduction in density of prolactin receptors and down-regulation of milk synthesis

Question 5

What is Posilac (bovine somatotropin) used for?

Answer 5

Given at peak lactation to extend and maintain peak production

Question 6

Describe the dangers of using bovine somatotropin (bST)

Answer 6

bST may increase risk of metabolic disorders as increased milk production => increased energy demand => can lead to negative energy balance => can contribute to ketosis and hepatic lipidosis