Reproductive Function Tests

Since ovulation may occur at varying times after the onset of vulval bleeding, progesterone measurement can used to determine the optimum time for mating. For most bitches, blood sampling for progesterone measurement should begin around 7 days after the onset of vulval swelling and bleeding. Bitches are then re-tested every 2–3 days until ovulation occurs.

A. When the bitch is showing signs of oestrus there are several tests which can detect ovarian tissue

1. Vaginal smear - cytological changes in vaginal epithelium can be used to identify ovarian activity
   
2. Measurement of oestrogen - this increases in late anoestrus, prooestrus and early oestrus but then declines
   
3. Measurement of progesterone - this increases in late oestrus and remains high in dioestrus (ie for 60 days post ovulation).

B. When there are no signs of oestrus:

1. Anti-Mullerian Hormone - determines the spay status of dogs after they have reached the age of sexual maturity. AMH levels remain constant throughout the cycle. Animals that have been neutered will have undetectable levels of AMH. A positive AMH test indicates the presence of ovarian tissue, but a negative result does not fully exclude the presence of ovarian remnants. An inconclusive AMH result cannot distinguish between the intact and spayed conditions
2. In case of inconclusive results, stimulation testing may be required to induce production of oestrogen from the ovarian remnant with either hCG or GnRH:

a. Collect basal sample in gel or heparin tube to provide 1 ml serum/plasma

b. Inject hCG (Chorulon, Intervet) at a dose of 44 IU/kg IM

c. Take a second sample 2h later, separate the serum/plasma and label ‘post’

d. Request OESTRADIOL.

1. Anti-Mullerian Hormone - may be used as a cryptorchid test to detect testicular tissue. This test may also be used in young animals under 3 years old. AMH levels should be very low (undetectable) in correctly castrated animals
2. Dynamic testosterone test - used to diagnose cryptorchidism or to evaluate testicular function. In normal dogs there is significant variation in testosterone production throughout the day. Single samples could potentially be measured at a trough of production and so stimulation testing using hCG is usually performed to detect testicular tissue

a. Collect basal sample into a plain gel or heparin tube to give 1 ml serum /plasma

b. Inject hCG (Chorulon, Intervet) at a dose of 44 IU/kg IM

c. Collect second sample 60 – 120 minutes later

d. Separate the serum and label the tubes pre- and post and request TESTOSTERONE.