Rabbit Giving Birth

The birth weights of rabbits are rather variable, but it isin the interests of the rabbit breeder to strive towards ashigh birth weights as possible. The reason for this is thatthere is a considerable relationship between good birth weightand subsequent growth, development and ability to thrive.There are a number of factors which affect birth weight.Of these, that having the greatest influence is the size of themother. A doe weighing say 3 lbs. will on average haveyoung weighing about an ounce, whilst a doe weighing say12 lbs. may have young weighing as much as two and a halftimes this weight.

The number in the litter also greatly affects the weight ofindividuals. Young from a small litter may weigh twice asmuch as those from a large litter, other things being equal.Does fed well produce larger offspring than does 4.ed badly.In the same way as milk yield is increased by an improvingcondition, so are the birds weights of the young. It might be again stressed that it is the improving condition in thedoe which is important, not necessarily a high conditionthroughout pregnancy.

The length of time which the young are carried, and theage of the mother have some slight influence. The shorterthe gestation period, and the younger the doe, the lighterwill be the individual weights of young produced.

It is often argued that males are heavier than females atbirth. This is not so, and all evidence tends to prove thatthere is no difference its weight related to sex.
The secondary sex ratio (that is the number of males perhundred females at birth) may vary, but it is almost certainlyinfluenced by inherited tendencies. Figures for very largecalculations of the secondary sex ratio have in two casesgiven results of 95 males per too females and 105 males pertoo females. Generally speaking how-ever, it is often foundthat slightly mare males than females are produced. Thereis evidence that rather more males are produced at con-ception than females, for it is known that the pre-birth deathrate is usually slightly higher for males than females.There appear to be many factors which influence this sexratio. In one experiment, numerous repeated matings atthe same time by the same buck showed a great decrease inthe number of males produced in the litters from these matings.In the first matings the ratio was T 29 males per too females,but this dropped to 28 males per too females in litters result-ing from the loth matings on the sarne day, by the samebuck. When two pure breeds are mated together, thenumber of males may be high, as also will it be during theearly part of the spring and summer. The proportion ofmales may also increase as the doe produces further litters.