CS: Applied reproductive endocrinology

Question 1

What bodyweight do heifers need to be in order to cycle?

Answer 1

60% adult bodyweight (this is generally more important than age - heifers tend to reach puberty at 7-18 months of age)

Question 2

How do you test to see if a heifer is a freemartin?

Answer 2

Insert well-lubricated tube into the vagina.
Short, blind ending vagina in freemartins. (8-10 cm whereas in normal adult cows ~30 cm. In calves 1-4 weeks old the vagina should be 13-15cm but a freemartin calf would have a length of 5-6cm).
No apparent cervix (rectal palpation)
Streaky structures instead of well-defined ovaries (rectal)

Question 3

What sophisticated tests can confirm a high index of suspicion for freemartins?

Answer 3

XX and XY patterns in freemartins
E2 and P4 assay (both would be low)
Detection of 2 different blood types within the same animal

Question 4

What do mullerian ducts develop into?

Answer 4

Internal female genitalia -uterus, cervix, upper vagina and oviducts.

Question 5

What do Wollfian ducts form?

Answer 5

Internal male genitalia - epididymis, vas deferens and accessory glands

Question 6

What controls the formation of the gonads?

Answer 6

SLY presence (testes)
SLY absence (ovaries)

Question 7

Outline formation of external male genitalia

Answer 7

• Testosterone needs to be converted into dihydro-testosterone through the enzyme (5-alpha reductase which is lovated on the genital tubercle) which makes an even more potent form of testosterone. This causes the formation of the external male genitalia (penis and scrotum). This is what happens in normal XY development.

Question 8

What male factors cause a female freemartin? 2

Answer 8

Testosterone - Leydig cells

MRF = Mullerian Regression Factor - Sertoli cell

Question 9

Outline the anatomy behind freemartin formation

Answer 9

Separate amnion

Shared chorioallantoic sac –> more likely to have BV anastomoses when closely apposed.

Question 10

Can sheep have freemartins?

Answer 10

Yes - less common than in cattle.
But risk increased with 4 or more lambs due to the increased demand for space in the uterus and thus the potential closer apposition and anastomoses of BVs from different sex foetuses.
Probably under-reported because of the age lambs are sent for slaughter.