Technical Measures for Improving the Reproduction Rate in Rex Rabbit Breeding

1 Improving Mating Methods

Adopting repeated mating or double mating can significantly increase the conception rate and litter size of does. Repeated mating means that after the first mating, at an interval of 4-6 hours, the same buck is used to mate once more. Double mating means that 1 doe is mated successively with 2 bucks, with the interval between them not exceeding 20-30 minutes.

Double mating can increase the conception rate of does by 10%-20% and increase the litter size by 1-3 young. It is worth noting that when double mating is used, the doe should be promptly returned to her original cage after mating with the first buck, and only after the buck's odor has dissipated should she be mated with the second buck. Otherwise, the odor of another buck on the doe's body will cause fighting, which will not only prevent successful mating but may also bite and injure the doe.

2 Increasing Breeding Density

In general rabbit farms, most young rabbits are weaned at 40-45 days of age, and then the doe is mated again. Therefore, only 3-4 litters can be bred per year, and the breeding speed is very slow. If feeding and management conditions are relatively good, intensive breeding or semi-intensive breeding can be implemented to increase the breeding density. Because the mating time in intensive breeding is relatively close to the time of kindling and littering, this kind of mating is commonly called "blood mating," that is, mating is carried out within 1-3 days after the doe gives birth, which can shorten the breeding interval by 20-30 days and allow 8-10 litters per year; semi-intensive breeding means that the doe is mated within 12-15 days after giving birth, which can shorten the breeding interval by 8-10 days and increase the number of litters per year by 3-4. It should be pointed out that after blood mating in does, because lactation and pregnancy proceed simultaneously, the demand for nutrients is very large, and the quantity and quality of feed must meet the needs of the doe itself as well as lactation and fetal growth and development. In addition, does must be weighed regularly, and if a significant loss of body weight is found, the next blood mating should be stopped. Because the use of intensive breeding shortens the service years of breeding rabbits, generally not exceeding 1.5-2 years, the natural culling rate is relatively high. Therefore, the breeding doe herd must be updated in a timely manner, and the young rabbits kept for breeding must have their feeding and management strengthened.

3 Using Artificial Estrus Induction

Some does affect reproduction because they do not come into estrus for a long time or refuse to mate, especially in autumn and winter. In order to make does come into estrus and mate, in addition to improving feeding and management, artificial estrus induction methods can also be used.

3.1 Hormone Estrus Induction

The hormones that promote estrus and ovulation in does mainly include follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secreted by the anterior pituitary, as well as chorionic gonadotropin (HCG) secreted by the placenta and pregnant mare serum gonadotropin (PMSG), etc. According to experiments, intramuscular injection of follicle-stimulating hormone (2 times daily, 0.6 mg per rabbit each time), intravenous injection of luteinizing hormone (10 units per rabbit each time), intramuscular injection of chorionic gonadotropin (50-100 units per rabbit each time), or pregnant mare serum gonadotropin (40 units per rabbit each time by intramuscular injection) can generally make the estrus rate of does reach 70%-90%, the conception rate reach 65%-70%, and the average litter size 4-6 young.

3.2 Sexual Induction of Estrus

For does that do not come into estrus for a long time or refuse to mate, the sexual induction method can be used. Place the doe in the buck's cage, and after stimulation through chasing, mounting, and so on, still return the doe to her original cage. After 2-3 times, the doe can be induced to secrete sex hormones, promoting estrus and ovulation. Generally, estrus is induced in the morning and mating is done in the evening.