macksmom98":1khlfn5d said:
I am kind of concerned about the whole possibility of 2 litters different dates same Doe thing. Do ya all worry about that?
Anything is
possible, but "dual pregnancies" would be incredibly rare, if they happen at all. I have copied the text from this post
post223088.html#p223088 I wrote quite some time ago which explains why it would be highly unlikely:
Rabbits are induced ovulators, which means that they release the eggs on stimulation from the buck. They do have cycles of receptivity as indicated by the color of the vulva. Dark pink or purple indicates that she has follicles that are ready to burst and release eggs. If she is mounted when follicles aren't ready, none will be released.
During their receptive window, there are "waves" of follicles maturing at different rates. Once a follicle reaches a certain size and is ready to rupture, but the doe is not bred, it will regress and never be viable again. At that point another "wave" of follicles will be maturing and may be ready to be released.
Breeding her to another buck will not cause release of a secondary "wave" of eggs, because they will not yet be mature.
Some people claim that does can carry two pregnancies of different gestational age, but this is not possible due to the hormonal changes that occur when eggs are released.
I'm about to get technical on you, :explanation: but am trying to keep it relatively simple, so here goes:
When the eggs are released the follicle is called a corpus hemorrhagicum, but the cells change to become a corpus luteum. The corpus luteum produces relatively high levels of progesterone and moderate levels of other hormones such as estrogen to inhibit further production of follicle stimulating hormones, preventing the growth of new follicles and release of eggs.
The corpus luteum remains in the ovary while the eggs traverse the fallopian tubes, continuing to secrete progesterone to prepare the uterus for implantation of the embryo(s). When the egg implants itself, it releases another hormone (HCG) which signals the corpus luteum to continue secreting progesterone to maintain the thick lining and increased blood vessels to the uterus to maintain growth of the embryos. Eventually, the placenta takes over and the corpus luteum degrades.
If the eggs are not fertilized and implantation fails to occur, the corpus luteum stops progesterone production and decays, allowing the receptive cycle to resume.
Further proof:
In most mammals the progesterone secreted during gestation inhibits oestrus and the pregnant female refuses to mate, but a pregnant doe may accept mating throughout the gestation period. Indeed, in the second half of pregnancy this is the most common behaviour (Figure 10).
A breeder cannot therefore use the sexual behaviour of does as an indication of pregnancy. Mating occurring during gestation has no dire consequences for the embryos. Unlike the phenomenon observed in the female hare, superfoetation (two simultaneous pregnancies at two different stages of development) never occurs in rabbits.
http://www.fao.org/docrep/t1690E/t1690e05.htm
