Reproductive Cyclicity in Females: Anestrus

Question 1

What is anestrus?

Answer 1

A lack of cycling.

Question 2

What are the six causes of anestrus?

Answer 2

1. Pathology (controlled by humans).
2. Stress (controlled by humans).
3. Nutrition (controlled by humans).
4. Season (Long day breeder v. Short day breeder).
5. Pregnancy.
6. Presence of offspring (lactation).

Question 3

What is gestational anestrus?

Answer 3

Negative feedback by P4 on the hypothalamus prevents LH and FSH from increasing and causing follicle development.

Question 4

Why does anestrus continue after parturition?

Answer 4

Extended P4 exposure for the hypothalamus leaves it less responsive to positive feedback from E2.
This allows time for uterine involution.

Question 5

What is seasonal anestrus?

Answer 5

When estrus only occurs during specific parts of the year. This changes based on the amount of daylight (which is controlled by location).

Question 6

How does the amount of daylight affect short-day breeders?

Answer 6

1. Less light enters the retina, decreasing retinal nerve firing.
2. Decreased pineal gland inhibition, increasing melatonin release.
3. High melatonin stimulates the hypothalamus, increasing GnRH, FSH, and LH, and stimulating the gonads.

Question 7

How does the amount of daylight affect long-day breeders?

Answer 7

1. Less light enters the retina, decreasing retinal nerve firing.
2. Decreased pineal gland inhibition, increasing melatonin release.
3. High melatonin stimulates decreased GnRH, FSH, and LH; the gonads are not stimulated.

Question 8

What are the two populations of receptors in the hypothalamus?

Answer 8

1. The surge center for the GnRH surge.
2. Reproductive behavior (needs to be exposed to P4 to form E2 receptors).

Question 9

At what two points can a silent ovulation occur?

Answer 9

1. Puberty.
2. After anestrus.

Question 10

What is lactational anestrus?

Answer 10

When the LH levels in the blood are kept high by the offspring continuing to suckle (at least 3 times per day).

Question 11

True or False: Lactational anestrus is caused by strictly nervous stimulation.

Answer 11

False.
It is also linked to olfactory, visual, auditory, and PRL (inhibits GnRH release).

Question 12

What is nutritional anestrus?

Answer 12

When a low BCS or a high BCS causes a high % anestrus.