The leech is a seasonal breeding animal and estrus is mated at the end of February each year. It is born late April to May. The mother's gestation period is 472 days. The average number of litters was 6.5. If the number of litters in the field is 2-5, the average is less than 4 and the number of litters is less. In production practice, the number of litters has fewer causes.

1. Genetic factors. Some leeches themselves are born less because of genetics. No matter how feed management is produced 2-3 only. When selecting the seedlings, pay attention to the elimination of seedlings that have fewer litters, and select the mothers that produce more than 8 fetuses as their seedlings. Strict selection, can not make do. For those who have lots of calves and low survival rates, they should not be left to plant, and must be eliminated to fundamentally improve the breeding performance of leech.

2. Prepare feeding and management factors for breeding period. Some fields are prepared for malnutrition or mismanagement during the breeding period, resulting in insufficient follicular development, less mature follicles, and not obvious otter estrus, implicit estrus, short estrus, and low litter size. For example, in the later period of the mating period, over-adjustment of the body condition will result in slow or stagnant ovarian growth and less mature follicles, which will reduce the number of litters. In addition, some animal feeds that are prepared for breeding in the open field are not fresh, the added vitamin E is insufficient, the female reproductive organs are not fully developed, the uterus and ovaries are naïve, and the number of litters is reduced or not estrus. It is difficult to mate. One reason.

The central task of preparing the breeding period is to promote the normal development of leeches reproductive organs and adjust the body condition. The diet should be supplied with sufficient vitamin A, vitamin E and B vitamins to ensure the normal development of the genital blister.

3. Public money factor. The quality of semen of public eel declined. In production practice, it was found that there were many farrowing mothers in some breeding farms, and there were fewer litters in later mating. This was due to excessive male-female breeding, and the quality of seminal semen was reduced. Little less. For example, there are 122 female breeding farms, 35 male breeding stalls, and 13 breeding couples who have sexual desires and can breed. The remaining 22 males have no sexual desire and cannot breed. Only 13 species of male cubs can be used with 122 female quails, and male cubs are used excessively and semen quality is reduced. As a result, there were more than 5 litters of females that had just started mating, with 10 individuals alone and an average of 6 litters. The estrus was late, and the mating females in the later period had reduced semen quality due to excessive breeding of public funds, and the number of litters was between 2-4.

To solve the problem that male-family male-female breeds cannot be bred, the breeding management must be strengthened during the preparation of the breeding period so that the male-female testes can develop normally, and the testicular softening and low sexual desire can be prevented. The use of male rations should be based on animal feed, accounting for 70%-75%, vegetable feed 18%-20%, vegetables 3%-5%, vegetable oil 1%, mineral additives 0.1 %, salt 0.5%. In addition, 800 IU of cod liver oil, 10 mg of vitamin E, and 20 mg of vitamin C were added daily to each species in the diet. The total amount of rations for each type of male commonweed is 350-400 grams.

4. Incorrect feeding and management during pregnancy. The mother-in-law controls the body condition during pregnancy, controls excessive fat, reduces the supply of fat in the feed, and makes the pregnancy leeches always maintain an upper body condition. For example, in a certain market, no attention is paid to feed during pregnancy, and broiler sausages, fat pork, etc. are still used during pregnancy. There is too much fat in the feed, nutrition is sufficient, the hair is bright, and the mother's fat is too fat. As a result, the gestation period is prolonged and the mother is degenerated. The fetuses and embryos are absorbed and the number of litters is reduced. Generally, the number of litters per mother is below 6 and most of the animals are 2-4, and the average number of litters is 2.7. There are a small number of female calves. The fetus did not produce a final one.

Pregnancy must control the amount of fat feed, each leeches daily intake of fat should not exceed 8-12 grams. It is strictly forbidden to use broiler intestine, fat pork and other fat-containing feeds during pregnancy to prevent overhydration during pregnancy.

5. Inbreeding. Some markets do not pay attention to breed replacement, excessive mating, making the number of litter reduced. If there is no exchange of public funds in a certain market for three years, the close relatives of the herds will be severely mated. As a result, the number of litters will be reduced. There will be 3-5 births and the average number of litters will be four. In the following year, after the introduction of public breeding, the same feeding and management methods were used, and the average number of litters was 5.5. Therefore, try to avoid inbreeding.

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