How can the reproductive rate of Rex rabbits be improved? These 12 measures are very effective
12 effective measures to improve the reproductive rate of Rex rabbits
1. Strictly select breeds. When selecting excellent male and female rabbits to keep for breeding, attention should be paid not only to their production performance (mainly meat production performance, such as daily weight gain, feed consumption, dressing percentage, etc.), but also to their reproductive performance. For breeding rabbits, if reproductive performance is not high, no matter how high past production performance (referring to weight gain and feed consumption during the growing period) was, its value for use is not great. Therefore, when selecting breeding stock, reproductive performance must be taken as an important indicator. Breeding rabbits should be selected and retained from the offspring of high-yielding breeding rabbits; the selected breeding rabbits should have well-developed reproductive organs, male rabbits should have large and symmetrical testes, high sperm viability, high sperm density, strong libido, and moderate fatness. Female rabbits should have a long body and large abdomen, with more than 8 teats; promptly cull male and female rabbits with a single testis, cryptorchidism, incomplete ovarian or uterine development, or reproductive organ diseases.
2. Appropriate male-to-female ratio. The intensity of use of male rabbits has a relatively large effect on the conception rate of female rabbits. Generally speaking, under natural mating conditions, the ratio of male rabbits to female rabbits is 1:8-12, with an additional 10% of the total number of male rabbits kept in reserve. Male rabbits are generally mated 1-2 times per day, for 2-3 consecutive days followed by 1 day of rest. If overused, male rabbits will experience physical exhaustion and testicular function failure, leading to premature aging, and the mating conception rate will instead decrease. However, long-term non-use of male rabbits is also unfavorable. This will inhibit testicular function, cause the sperm stored in the epididymis to age, reduce vitality, and even die, not only lowering the conception rate, but also increasing the number of stillborn and weak fetuses and reducing the number of kits per litter.
3. Maintain the body condition of breeding rabbits. The body condition of breeding rabbits has a relatively large effect on conception rate and litter size. Being too obese causes fat deposition around the ovaries, affects their function, and can cause abnormal estrus or low conception rate and litter size. Being too thin and malnourished can also inhibit the sexual function of female rabbits. Therefore, maintaining breeding body condition, neither too fat nor too thin, that is, maintaining an 80% fat condition, can improve the estrus rate and mating conception rate. Practice has shown that in rabbit farms with the conditions to do so, increasing the feeding of green fodder can prevent female rabbits from becoming too fat, maintain good breeding condition, and improve reproductive capacity.
4. Strengthen feeding and management. Foreign research has pointed out that a high nutritional level often affects follicular development and reduces the ovulation rate of breeding female rabbits. According to observation of fertilized egg implantation on the 9th day after mating, the embryo mortality rate was 44% at the high nutritional level, while it was 18% at the low nutritional level; the former produced only 3.8 live kits, while the latter produced 6, indicating that maintaining the breeding body condition of breeding rabbits, neither too fat nor too thin, that is, medium fat condition, so that they have vigorous sexual function, is an important measure to improve the reproductive rate. For this reason, attention must be paid to feeding and management before and after mating, scientific feed formulation, and ensuring feed quality, so as to meet the nutritional needs of breeding rabbits and kits. Prevent the reproductive capacity of breeding rabbits from being affected by excessive toxic and harmful substances in the feed.
5. Increase vitamin feed. Vitamins have a relatively large effect on the reproductive rate of breeding rabbits. In particular, vitamin A and vitamin E play roles in the reproduction process of Rex rabbits that cannot be replaced by other nutrients. Their deficiency will cause reproductive disorders in Rex rabbits. For breeding rabbits during the reproductive period, the required supply of vitamin A and vitamin E in the feed should be guaranteed. Therefore, the feed should contain sufficient vitamins. Green fodder is rich in vitamins; providing a certain amount of green fodder year-round can reduce feed costs and improve conception rate and litter size.
6. Carry out crossbreeding between strains. In commercial Rex rabbit production, crossbreeding is an effective way to improve economic benefits. At present, the Rex rabbits raised in China include 3 types: the American line, the German line, and the French line. Practice has shown that using the American line Rex rabbit as the female parent and the German and French lines as the male parent for economic crossbreeding, the crossbred offspring are better than their parents in both growth and development and fur quality. Overall, the bloodlines of Rex rabbits raised in China are relatively narrow, and in production, especially in some small and medium-sized rabbit farms, there is more or less a certain degree of inbreeding. Therefore, consciously and purposefully carrying out crossbreeding between strains has certain practical significance for improving this narrow-bloodline situation.
7. Control temperature in summer and increase light in winter. Practice has shown that when female rabbits are exposed to different environmental temperatures during pregnancy, litter size differs. Under high temperature (above 30°C) conditions, the litter size of female rabbits is significantly reduced. In an environment below 25°C, there is a higher litter size. This is because under high temperature, embryo mortality increases. Rex rabbits are not demanding regarding light, but insufficient light can significantly affect reproductive performance. According to experiments, under conditions of 20-24°C and complete darkness, supplementing 1 watt of light per sq m for 2 hours, although female rabbits still have some fertility, the conception rate is very low, with the conception rate of a single mating being only about 30%. If the light is increased to 15 watts per sq m and the light duration is extended to 12 hours, the conception rate of a single mating is about 50%. Under the same light intensity, if irradiated for 16 hours, the conception rate of female rabbits reaches 65%-70%, and the survival rate of kits can also be significantly improved. Therefore, in winter and after autumn, a combination of natural light and artificial supplementary light should be adopted so that the daily light duration reaches 14-16 hours.
8. Carry out short-term flushing. In animal production there is a theory of "short-term flushing," that is, 2 weeks before mating of female livestock, increasing the energy content in the feed (that is, increasing the proportion of feeds containing more energy, such as corn and wheat bran, so that energy is increased by 20%-30%) can increase the number of ovulations. However, after mating, the energy should be reduced immediately. Otherwise, it will increase embryo mortality.
9. Improve semen quality. The mating conception rate is affected by the conditions of both female and male rabbits. In production, infertility caused by male rabbits seems to be more common and should be taken seriously. For breeding male rabbits, in addition to body condition, nutrition, vitamins, and disease, the testes of male rabbits are particularly sensitive to high temperature. Continuous high temperature in summer will cause degeneration of the spermatogenic epithelium of the male rabbit's testes, temporarily losing the ability to produce sperm, and the recovery of its function requires a relatively long time (generally 40-60 days). Therefore, in the high-temperature season, special emphasis should be placed on providing breeding male rabbits with a suitable low-temperature environment, which is an effective measure to improve the conception rate and litter size of Rex rabbits. In rabbit farms with the conditions to do so, breeding male rabbits can be concentrated in an air-conditioned room to spend the summer during the hot summer, and doing so is economically worthwhile. Timely use of anti-heat-stress preparations for male rabbits subjected to heat stress has a good effect on preventing stress and accelerating the recovery of testicular function in male rabbits.
10. Implement scientific mating. ① Mate during the mid-estrus period of female rabbits, when the conception rate is highest, and avoid inbreeding. ② Use repeat mating and double mating. During the estrus period of a female rabbit, using 1 male rabbit to mate 2 or more times (generally at an interval of 4 hours) is called repeat mating; if 2 male rabbits are used to mate with the same estrous female rabbit (generally at an interval of more than 15 minutes and within 4 hours), it is called double mating. Both methods can improve the conception rate and litter size of female rabbits. ③ Hormone-assisted mating. According to experiments, while carrying out natural mating of Rex rabbits, additionally injecting the female rabbit intramuscularly with ovulation-promoting hormone No. 3 can not only improve the conception rate but also increase litter size. ④ Reduce summer breeding. In rabbit farms without cooling conditions, mating should be stopped during the high-temperature period in summer. In doing so, the number of litters of female rabbits may seem to decrease, but it can ensure the physical condition of breeding rabbits and maintain vigorous reproductive capacity. ⑤ Appropriate postpartum mating. Female rabbits have the characteristic of postpartum estrus. For young and strong female rabbits with a relatively small litter size, if their body condition is good, they can be mated within 24 hours after giving birth (experiments show that mating 6-12 hours after giving birth has the best effect), and both the conception rate and litter size are relatively high. However, for female rabbits in poor fat condition, even if they conceive after mating, it will lead to poor fetal development, decline in the female rabbit's physical condition, and a relatively large impact on both litters of kits and the female rabbit's subsequent reproduction. 11. Induce estrus. Some female rabbits 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 female rabbits estrus and mate, in addition to improving feeding and management, artificial methods of inducing estrus can also be adopted to promote estrus and carry out mating in time. ① Sexual induction of estrus. For female rabbits that do not come into estrus for a long time or refuse to mate, the sexual induction method can be used. Place the female rabbit in the male rabbit's cage, and after about half an hour of stimulation through chasing, mounting, and the like, return the female rabbit to its original cage. After 2-3 times, the female rabbit can be induced to secrete sex hormones, promoting estrus and ovulation. Generally, induce estrus in the morning, and about 8 hours later, place the female rabbit in the male rabbit's cage for mating. ② Scent induction of estrus. Exchange the cage positions of the male and female rabbits for one day and night so that the female rabbit is exposed to the male rabbit's scent. The next day the female rabbit will come into estrus; put the male rabbit back in the original cage to mate with the female rabbit. ③ Massage induction of estrus. Hold the female rabbit by both ears and the neck with the left hand to restrain it, and gently massage (or quickly pat) the external genitalia with the right hand. When the female rabbit raises its hindquarters, place it in the male rabbit's cage for mating. ④ Stimulation induction of estrus. Apply a small amount of cooling oil or 2% dilute iodine tincture to the female rabbit's external genital lips, and after 30 minutes place it in the male rabbit's cage for mating. It is reported that the success rate can reach about 70%. ⑤ Hormone induction of estrus. Intramuscular injection of pregnant mare serum gonadotropin at 50-80 units per female rabbit or triple hormone at 0.75-1 mL per rabbit can be used, with mating 6 hours after injection. Ovulation-promoting hormone No. 3 can also be used by intramuscular injection at 5 micrograms per female rabbit, with mating during the period 5-8 hours after injection. ⑥ Feed induction of estrus. Wheat can be germinated for 2-3 days and then mixed into concentrated feed, twice a day, 20-30 grams each time, and results can be seen after 3 consecutive days of feeding; carrots can also be cut into fine dice and mixed into concentrated feed, twice a day, 50-100 grams each time, and after 2 days the female rabbit will come into estrus and mate.
12. Promptly diagnose and treat diseases. Any disease in Rex rabbits will affect the reproductive rate. In particular, reproductive system diseases, such as metritis, vaginitis, syphilis, orchitis, etc., should be diagnosed and treated promptly. However, when preventing and treating diseases, do not use drugs in large amounts, for long periods, or blindly, and try not to use drugs or inject vaccines during the mating period of Rex rabbits. ① Environment. Clean the rabbit cages and rabbit houses frequently and promptly, do a good job of environmental sanitation, and keep the rabbit house ventilated, well-lit, dry, and quiet. ② Disinfection. In summer, disinfect once every 10 days; in winter, disinfect once a month. The disinfectants are: Lysol, disinfectant solution, caustic soda, etc. ③ Medicated bath. In spring, summer, and autumn, use medicated water (trichlorfon 3%, amitraz 0.01%, fenvalerate 0.01%) for one medicated bath each to prevent skin diseases, foot and ear mange, and other diseases. ④ Epidemic prevention. Kits should be injected 3-4 times a year with rabbit plague vaccine and Pasteurella vaccine to enhance the Rex rabbit's own resistance and improve and accelerate the growth and development of Rex rabbits. ⑤ Culling. Old, weak, diseased, and disabled rabbits with little breeding value should be decisively culled.
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15 watts per sq m, and the light duration is extended to 12 hours, then the conception rate of a single mating is about 50%
2. Appropriate male-to-female ratio. The intensity of use of male rabbits has a relatively large effect on the conception rate of female rabbits. Generally speaking, under natural mating conditions, the ratio of male rabbits to female rabbits is 1:8-12, with an additional 10% of the total number of male rabbits kept in reserve. Male rabbits are generally mated 1-2 times per day, for 2-3 consecutive days followed by 1 day of rest. If overused, male rabbits will experience physical exhaustion and testicular function failure, leading to premature aging, and the mating conception rate will instead decrease. However, long-term non-use of male rabbits is also unfavorable. This will inhibit testicular function, cause the sperm stored in the epididymis to age, reduce vitality, and even die, not only lowering the conception rate, but also increasing the number of stillborn and weak fetuses and reducing the number of kits per litter.
3. Maintain the body condition of breeding rabbits. The body condition of breeding rabbits has a relatively large effect on conception rate and litter size. Being too obese causes fat deposition around the ovaries, affects their function, and can cause abnormal estrus or low conception rate and litter size. Being too thin and malnourished can also inhibit the sexual function of female rabbits. Therefore, maintaining breeding body condition, neither too fat nor too thin, that is, maintaining an 80% fat condition, can improve the estrus rate and mating conception rate. Practice has shown that in rabbit farms with the conditions to do so, increasing the feeding of green fodder can prevent female rabbits from becoming too fat, maintain good breeding condition, and improve reproductive capacity.
4. Strengthen feeding and management. Foreign research has pointed out that a high nutritional level often affects follicular development and reduces the ovulation rate of breeding female rabbits. According to observation of fertilized egg implantation on the 9th day after mating, the embryo mortality rate was 44% at the high nutritional level, while it was 18% at the low nutritional level; the former produced only 3.8 live kits, while the latter produced 6, indicating that maintaining the breeding body condition of breeding rabbits, neither too fat nor too thin, that is, medium fat condition, so that they have vigorous sexual function, is an important measure to improve the reproductive rate. For this reason, attention must be paid to feeding and management before and after mating, scientific feed formulation, and ensuring feed quality, so as to meet the nutritional needs of breeding rabbits and kits. Prevent the reproductive capacity of breeding rabbits from being affected by excessive toxic and harmful substances in the feed.
5. Increase vitamin feed. Vitamins have a relatively large effect on the reproductive rate of breeding rabbits. In particular, vitamin A and vitamin E play roles in the reproduction process of Rex rabbits that cannot be replaced by other nutrients. Their deficiency will cause reproductive disorders in Rex rabbits. For breeding rabbits during the reproductive period, the required supply of vitamin A and vitamin E in the feed should be guaranteed. Therefore, the feed should contain sufficient vitamins. Green fodder is rich in vitamins; providing a certain amount of green fodder year-round can reduce feed costs and improve conception rate and litter size.
6. Carry out crossbreeding between strains. In commercial Rex rabbit production, crossbreeding is an effective way to improve economic benefits. At present, the Rex rabbits raised in China include 3 types: the American line, the German line, and the French line. Practice has shown that using the American line Rex rabbit as the female parent and the German and French lines as the male parent for economic crossbreeding, the crossbred offspring are better than their parents in both growth and development and fur quality. Overall, the bloodlines of Rex rabbits raised in China are relatively narrow, and in production, especially in some small and medium-sized rabbit farms, there is more or less a certain degree of inbreeding. Therefore, consciously and purposefully carrying out crossbreeding between strains has certain practical significance for improving this narrow-bloodline situation.
7. Control temperature in summer and increase light in winter. Practice has shown that when female rabbits are exposed to different environmental temperatures during pregnancy, litter size differs. Under high temperature (above 30°C) conditions, the litter size of female rabbits is significantly reduced. In an environment below 25°C, there is a higher litter size. This is because under high temperature, embryo mortality increases. Rex rabbits are not demanding regarding light, but insufficient light can significantly affect reproductive performance. According to experiments, under conditions of 20-24°C and complete darkness, supplementing 1 watt of light per sq m for 2 hours, although female rabbits still have some fertility, the conception rate is very low, with the conception rate of a single mating being only about 30%. If the light is increased to 15 watts per sq m and the light duration is extended to 12 hours, the conception rate of a single mating is about 50%. Under the same light intensity, if irradiated for 16 hours, the conception rate of female rabbits reaches 65%-70%, and the survival rate of kits can also be significantly improved. Therefore, in winter and after autumn, a combination of natural light and artificial supplementary light should be adopted so that the daily light duration reaches 14-16 hours.
8. Carry out short-term flushing. In animal production there is a theory of "short-term flushing," that is, 2 weeks before mating of female livestock, increasing the energy content in the feed (that is, increasing the proportion of feeds containing more energy, such as corn and wheat bran, so that energy is increased by 20%-30%) can increase the number of ovulations. However, after mating, the energy should be reduced immediately. Otherwise, it will increase embryo mortality.
9. Improve semen quality. The mating conception rate is affected by the conditions of both female and male rabbits. In production, infertility caused by male rabbits seems to be more common and should be taken seriously. For breeding male rabbits, in addition to body condition, nutrition, vitamins, and disease, the testes of male rabbits are particularly sensitive to high temperature. Continuous high temperature in summer will cause degeneration of the spermatogenic epithelium of the male rabbit's testes, temporarily losing the ability to produce sperm, and the recovery of its function requires a relatively long time (generally 40-60 days). Therefore, in the high-temperature season, special emphasis should be placed on providing breeding male rabbits with a suitable low-temperature environment, which is an effective measure to improve the conception rate and litter size of Rex rabbits. In rabbit farms with the conditions to do so, breeding male rabbits can be concentrated in an air-conditioned room to spend the summer during the hot summer, and doing so is economically worthwhile. Timely use of anti-heat-stress preparations for male rabbits subjected to heat stress has a good effect on preventing stress and accelerating the recovery of testicular function in male rabbits.
10. Implement scientific mating. ① Mate during the mid-estrus period of female rabbits, when the conception rate is highest, and avoid inbreeding. ② Use repeat mating and double mating. During the estrus period of a female rabbit, using 1 male rabbit to mate 2 or more times (generally at an interval of 4 hours) is called repeat mating; if 2 male rabbits are used to mate with the same estrous female rabbit (generally at an interval of more than 15 minutes and within 4 hours), it is called double mating. Both methods can improve the conception rate and litter size of female rabbits. ③ Hormone-assisted mating. According to experiments, while carrying out natural mating of Rex rabbits, additionally injecting the female rabbit intramuscularly with ovulation-promoting hormone No. 3 can not only improve the conception rate but also increase litter size. ④ Reduce summer breeding. In rabbit farms without cooling conditions, mating should be stopped during the high-temperature period in summer. In doing so, the number of litters of female rabbits may seem to decrease, but it can ensure the physical condition of breeding rabbits and maintain vigorous reproductive capacity. ⑤ Appropriate postpartum mating. Female rabbits have the characteristic of postpartum estrus. For young and strong female rabbits with a relatively small litter size, if their body condition is good, they can be mated within 24 hours after giving birth (experiments show that mating 6-12 hours after giving birth has the best effect), and both the conception rate and litter size are relatively high. However, for female rabbits in poor fat condition, even if they conceive after mating, it will lead to poor fetal development, decline in the female rabbit's physical condition, and a relatively large impact on both litters of kits and the female rabbit's subsequent reproduction. 11. Induce estrus. Some female rabbits 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 female rabbits estrus and mate, in addition to improving feeding and management, artificial methods of inducing estrus can also be adopted to promote estrus and carry out mating in time. ① Sexual induction of estrus. For female rabbits that do not come into estrus for a long time or refuse to mate, the sexual induction method can be used. Place the female rabbit in the male rabbit's cage, and after about half an hour of stimulation through chasing, mounting, and the like, return the female rabbit to its original cage. After 2-3 times, the female rabbit can be induced to secrete sex hormones, promoting estrus and ovulation. Generally, induce estrus in the morning, and about 8 hours later, place the female rabbit in the male rabbit's cage for mating. ② Scent induction of estrus. Exchange the cage positions of the male and female rabbits for one day and night so that the female rabbit is exposed to the male rabbit's scent. The next day the female rabbit will come into estrus; put the male rabbit back in the original cage to mate with the female rabbit. ③ Massage induction of estrus. Hold the female rabbit by both ears and the neck with the left hand to restrain it, and gently massage (or quickly pat) the external genitalia with the right hand. When the female rabbit raises its hindquarters, place it in the male rabbit's cage for mating. ④ Stimulation induction of estrus. Apply a small amount of cooling oil or 2% dilute iodine tincture to the female rabbit's external genital lips, and after 30 minutes place it in the male rabbit's cage for mating. It is reported that the success rate can reach about 70%. ⑤ Hormone induction of estrus. Intramuscular injection of pregnant mare serum gonadotropin at 50-80 units per female rabbit or triple hormone at 0.75-1 mL per rabbit can be used, with mating 6 hours after injection. Ovulation-promoting hormone No. 3 can also be used by intramuscular injection at 5 micrograms per female rabbit, with mating during the period 5-8 hours after injection. ⑥ Feed induction of estrus. Wheat can be germinated for 2-3 days and then mixed into concentrated feed, twice a day, 20-30 grams each time, and results can be seen after 3 consecutive days of feeding; carrots can also be cut into fine dice and mixed into concentrated feed, twice a day, 50-100 grams each time, and after 2 days the female rabbit will come into estrus and mate.
12. Promptly diagnose and treat diseases. Any disease in Rex rabbits will affect the reproductive rate. In particular, reproductive system diseases, such as metritis, vaginitis, syphilis, orchitis, etc., should be diagnosed and treated promptly. However, when preventing and treating diseases, do not use drugs in large amounts, for long periods, or blindly, and try not to use drugs or inject vaccines during the mating period of Rex rabbits. ① Environment. Clean the rabbit cages and rabbit houses frequently and promptly, do a good job of environmental sanitation, and keep the rabbit house ventilated, well-lit, dry, and quiet. ② Disinfection. In summer, disinfect once every 10 days; in winter, disinfect once a month. The disinfectants are: Lysol, disinfectant solution, caustic soda, etc. ③ Medicated bath. In spring, summer, and autumn, use medicated water (trichlorfon 3%, amitraz 0.01%, fenvalerate 0.01%) for one medicated bath each to prevent skin diseases, foot and ear mange, and other diseases. ④ Epidemic prevention. Kits should be injected 3-4 times a year with rabbit plague vaccine and Pasteurella vaccine to enhance the Rex rabbit's own resistance and improve and accelerate the growth and development of Rex rabbits. ⑤ Culling. Old, weak, diseased, and disabled rabbits with little breeding value should be decisively culled.
--------------------------------------
15 watts per sq m, and the light duration is extended to 12 hours, then the conception rate of a single mating is about 50%