COMMERCIAL RABBIT RAISING 



29 



at all times during the breeding 

 season. There may be a transi- 

 tional period, while the new set of 

 follicles is growing and the old 

 set is retrogressing, when the doe 

 lacks interest in the male and i3 

 temporarily sterile. 



Ovulation usually does not occur 

 in the female unless she is mated 

 to a male. Following mating, the 

 large follicles in the ovary begin 

 to grow rapidly. These break 

 about 10 hours after mating. This 

 process of shedding the egg is 

 called ovulation. In the meantime 

 the sperm from the male move 

 through the female tract to the 

 upper part of the tubes so that 

 when the eggs are shed from the 

 follicles, the sperm enter and fer- 

 tilize them. These fertilized eggs 

 then undergo a number of changes 

 and grow to become the develop- 

 ing fetuses. The young fetuses 

 grow and develop in the uterus 

 and this period of development 

 usually takes 30 to 32 days. After 

 the eggs are shed, the cells that 

 line the follicles begin to grow and 

 form small yellow bodies in the 

 ovary, called the corpora lutea. 

 These bodies secrete a hormone 

 called progesterone, which is nec- 

 essary to cause the uteri to grow 

 and secrete substances that feed 

 the developing young. 



The practical method for meas- 

 uring fertility in does is to deter- 

 mine the total number of live 

 young born from each gestation. 

 The litter size varies with the 

 strain or breed, and the more fer- 

 tile strains will produce an aver- 

 age of about eight young per preg- 

 nancy. Many factors, such as nu- 

 trition, heredity, and environment, 

 affect fertility. Does that are un- 

 derfed will not come in heat, and 

 the quality of semen from starved 

 bucks is lowered. Also, though 

 experimental proof is lacking, 

 there is a widespread opinion that 



does and bucks which are exces- 

 sively fat have lowered reproduc- 

 tive capacities due to decreased 

 sexual urge, or libido, or inter- 

 ference with the passage of eggs 

 and sperm in the small reproduc- 

 tive tubules. Hereditary charac- 

 ters that affect fertility in does are 

 number of eggs shed and fetal mor- 

 tality. In highly fertile strains, 

 the number of eggs shed averages 

 about 10, while in low strains, the 

 number may only be 4 or 5. In 

 some low-fertility strains, normal 

 numbers of ova are shed but an 

 abnormally large number of em- 

 bryos die during gestation. In 

 fertile strains, about 15 to 20 per- 

 cent of the fetuses die in the uterus 

 during gestation. In some low- 

 fertility strains, 80 percent of the 

 fetuses die during the gestation 

 period. 



Gestation Period 



The gestation period, or the pe- 

 riod from mating to kindling, is 

 31 or 32 days. Some litters may 

 be kindled as early as the 28th or 

 29th day, or as late as the 35th, but 

 98 percent of the normal litters 

 will be kindled between the 30th 

 and 33d day. If kindling is de- 

 layed 2 or 3 days, generally one 

 or more of the fetuses is unusually 

 large. 



Age to Breed 



The proper age of bucks and 

 does for the first mating depends 

 on breed and individual develop- 

 ment. Smaller breeds develop 

 more rapidly and are sexually ma- 

 ture at a much younger age than 

 medium-weight or giant breeds. 

 Does should be mated when they 

 reach maturity; some difficulty 

 may be experienced if mating is 

 too long delayed. On the average, 

 the smaller breeds may be bred 

 when the bucks and does are 4 to 



