Lecture 8 - Hormone driven nutrient utilization Flashcards
Diabetes mellitus in dairy cows.
Diabetes mellitus is considered to be a rare endocrine disease in dairy cows owing to its irreversible nature.
HERITABILITY of milk yield versus growth hormone traits
– Milk yield 0.28
– Growth hormone traits >0.6
During lactation, higher GH concentrations and lower IGF1 and insulin concentrations result in
more available nutrients being partitioned towards the mammary gland instead of other somatic processes.
Mechanisms which enable nutrient
prioritization in favor of milk production (3)
- The function of the pancreas decreases resulting in low blood insulin concentrations
- Reduced insulin causes energy mobilization and partitioning that energy into the udder
- the udder is insulin independent in glucose uptake
Endocrinology of the somatotrophic axis
before and after calving: late pregnancy. (3)
GH down
Insulin up
IGF1 up
energy is focused on fetal and somatic growth processes, anabolism.
Endocrinology of the somatotrophic axis
before and after calving: early post-calving. (3)
GH up
Insulin down
IGF1 down
energy is focused on production, lipolysis is favored.
Normal GH-IGF1- axis favoring anabolism:
Moderate growth hormone conct. acts on receptors in the liver, which produce IGF-1 in response which, together with insulin, has a positive protein synthesis and growth.
Simultaneously, while insulin levels are high, there is a negative effect on lipolysis. Lipids are not be utilized, they are being packed away.
(remember insulin “stores energy”/anabolic)
What types of states induce GH hypersecretory state. (3)
Fasting, calorie restriction or states of undernutrition.
What leads to GH resistance.
Physiological insults such as nutritional stress, or injury activate the hypothalamic-pituitary axis and elevated circulating glucocorticoids lead to GH resistance.
This happens after calving, the GH receptors are downregulated. GH is present but the response of IGF1 is very small.
Effect of moderate negative energy balance on ovulation.
In mod. neg. energy balance states, the pituitary secretes moderate GH concentrations, that then binds to hepatic IGF1 receptors which results in IGF1 secretion.
If there’s enough of IGF1 and insulin, stimulate the growth of follicles which then produce estradiol which in turns stimulates LH and thus ovulatory cyclicity.
Effect of deep negative energy balance on ovulation.
In deep neg. energy balance states, the pituitary secretes higher GH concentrations, but the liver becomes resistance to GH which means the GH receptors are downregulated and the release of iGF1 is very small.
Without sufficient IGF1 follicles will not grow, estradiol will not increase nor will ovulation.
Circulating IGF1 and insulin have what effect on follicles.
They synergize with FSH & LH, stimulate estradiol, follicle and oocyte growth.
Point is that insulin and IGF1 are needed for ovulatory cyclicity and good fertility.
Circulating IGF1 and insulin have what effect on CL.
They synergize with FSH & LH, stimulates progesterone.
Point is that insulin and IGF1 are needed for ovulatory cyclicity and good fertility.
