Rabbit Breed – How To Increase Size of Rabbit Litters
Information About Rabbit Breed
No matter for what purpose rabbit breed is kept, the size of litters is a matter of some concern. In the commercial field, the largest litters consistent with good growth are obviously desirable.
Rabbit breed Litter size is controlled by two different sets of factors. The first set is those of an inherited nature. The second includes those of the environment. Obviously the environmental factors will influence the doe only, but the inherited characters will affect both the buck and the doe.
Facts About Rabbit Breed Litter Size
Rabbit breed Litter size is affected at ovulation, at fertilization, and during pregnancy. At ovulation, a certain number of eggs are shed. Some of these may not be fertilized, and some of the fertilized eggs may die during pregnancy. The potential fecundity of the doe is, therefore, the maximum number of eggs sited at ovulation, whilst the actual fecundity is the number of young born in each litter.
There are two basic hereditary influences (Rabbit Breed)
In general, the larger the rabbit breed, the higher is the number of young produced in each litter. But at the same time, in strains of the same size, some hereditary factors occur for high or low fecundity. Thus in the stud where management and breed are the same for all animals, and large litter size is desired, preference should be given when selecting breeding stock to animals that have a high average litter size. This applies to the bucks as well as the does, for the inheritance of fecundity can be transmitted through the male line.
Inheritance of fecundity is not controlled in a simple way by one or two genes. Thus the inheritance of this characteristic blends over a wide range. Occasionally when extra-large animals are desired the breeder may unconsciously select breeding stock for smaller and smaller litter size. This is because he will often select for future breeding on the basis of size, and most frequently the size of young in small litters is greater than that of those in large litters.
Apart from inherited characteristics, nutrition, age of doe, number of previous litters and disease all have an effect on the final litter size.
Of these factors, nutrition is the most important. A rising condition will produce the largest litter, and poor nutrition, over fatness, a falling condition and so on will lead to small litters. Litters born during the spring and summer are often larger than those born at other times of the year. But this is probably correlated with the better feeding condition than, for when nutrition is standardized throughout the year these variations tend to disappear.
There is almost invariably an increase in litter size between the first and second litters, but thereafter depending on the strain, variation occurs. In some strains the litter size continues to increase for some litters, in others, it remains more or less stationary, in others it decreases. In some strains, an increase may be noted up to an age of some three years, but eventually, litter size decreases.
During the course of pregnancy, embryos may die for several reasons. There are one or two diseases that cause death, but the most important factor is an inherited one which causes fetal atrophy. This factor is recessive, and when present in a homozygous state in the doe (for the character occurs in the doe arid not in the embryos) the majority of embryos die.
Following the death of the embryo, it is either absorbed or aborted, depending mainly on the stage of pregnancy. In the early stages, the embryos are absorbed whilst later on, they are aborted.
Fertility, the ability to produce living young, and fecundity, a measure of the number of young produced, are closely connected. Strains showing high fertility are usually also highly fecund. But this general rule does not, of course, apply to the relationship between the weight of adult and litter size, for in this relationship the small breeds (early maturing sexually) have smaller litters than do large breeds (late-maturing sexually).