The bitch

Question 1

What is the biological basis of pseudopregnancy?

Answer 1

A long luteal phase with no luteolysis causes prolonged life of corpus luteum.
Prolactin increase causes large mammary glands. Sterile mating possibly but it is not a key
trigger.
Early abortion or pregnancy loss can cause a false pregnancy as the corpus luteum will have had the initial signals to produce progesterone the
pseudo-pregnancy will end when the L-P shift occurs and there is not fetus to create progesterone.
In goats the CL maintains the progesterone levels throughout entire pregnancy therefore pseudo-pregnancy can go on and on in goats.

Question 2

How does PGF2a induce oestrus?

Answer 2

PGF2a inhibits progesterone by breaking down the CL, this allows for a new dominant follicle to ovulate and a return to oestrous.

Question 3

How does induction of oestrus behaviour using administration of progesterone for several
days and then withdrawal of progesterone work?

Answer 3

Normally progesterone is involved in the maintenance of pregnancy in the luteal phase. There is normally a progesterone peak prior to ovulation. This means that when you withdraw the progesterone there
is a dominant follicle ready to ovulate. This is the same principle used in sponging
sheep. The pre-ovulatory rise in progesterone provides the stimulus for the bitch to
become receptive to the male.

Question 4

Define diestrus?

Answer 4

A period of sexual inactivity between recurrent periods of oestrus.

Question 5

Describe the phases of reproduction in the bitch?

Answer 5

1) Proestrus = is when they are in the follicular phase, but not receptive to the male.
2) Estrus = In the follicular phase and receptive to the male.
3) Metestrus = Early luteal phase, rise in progesterone after ovulation.
4) Diestrus = In the luteal phase when progesterone levels falling.
5) Anestrus = Not cycling. Gap between the two cycles, when the ovaries are kind of inactive.