Cause analysis and solution to the small number of mink litter

Mink

Minks are seasonal breeding animals that mate in estrus in late February and give birth from late April to May. The gestation period of female mink was 47 ±2 days. The average litter size was 6.5. If the number of minks born in the whole field is 2-5, with an average of less than 4, the number of minks is on the low side. In production practice, there are few reasons for the number of litters.

1. Genetic factors. Some minks themselves give birth to fewer babies, which is caused by heredity. No matter how they are raised and managed, they will produce 2-3 animals. In the selection, we should pay attention to eliminate the breed mink with less litter, and select the female mink with more than 8 births as the breeding mink. Strict seed selection can not make do. For those female minks that have a large number of offspring and low survival rate, they should not leave seeds and must be eliminated to fundamentally improve the reproductive performance of minks.

two。 Factors of feeding and management in preparation for mating period. Some mink farms are malnourished or poorly managed during the preparation and breeding period, resulting in insufficient development of mink follicles, few mature follicles, inobvious estrus, recessive estrus and short estrus, resulting in a small number of offspring. Such as the late period of preparation for mating, excessive adjustment of the body condition, so that the slow or stagnant development of the ovary, less mature follicles, so that the number of offspring reduced. In addition, the animal feed fed in some mink farms during the mating period is not fresh, the added vitamin E is insufficient, the reproductive organs of female minks are not fully developed, and the immature type of uterus and ovary is also one of the reasons why the litter size of minks decreases or does not come into estrus and it is difficult to breed.

The central task of preparing for mating period is to promote the normal development of mink reproductive organs and adjust their body condition. Adequate vitamin A, vitamin E and B vitamins should be provided in the diet to ensure the normal development of mink reproductive organs.

3. The male mink factor. The semen quality of male mink decreased. In the production practice, it was found that the early breeding of female mink in some mink farms gave birth more than that of later breeding, which was due to the over breeding of male marten and the decline of semen quality of male mink in the later stage. For example, there are 122 female minks in a mink farm, of which 35 are male minks, 13 have sexual desire and can be mated, and the other 22 male minks have no sexual desire and can not be mated. Only 13 species of male mink can be matched with 122 female mink. The male mink is overused and the semen quality is decreased. As a result, at the beginning of breeding, all the female minks gave birth to more than 5, individual 10, with an average of 6. However, for the female mink with late estrus and late mating, the semen quality decreased and the litter size was 2-4 due to over-mating of male mink.

In order to solve the problem that male mink can not be mated, it is necessary to strengthen feeding and management during the period of preparation for breeding, so as to make the testicular development of male marten normal, prevent testicular malacia and low libido. The diet of male minks should be based on animal feed, accounting for 70%, 75%, 18%, 20%, 3%, 5%, 1%, 0.1% and 0.5%, respectively. In addition, each male mink in the diet is supplemented with 800 international units of cod liver oil, 10 mg of vitamin E and 20 mg of vitamin C. The total diet of each male mink is 350-400 grams.

4. Improper feeding and management during pregnancy. During pregnancy, female minks should control their body condition, prevent and cure overweight, and reduce the supply of fat in feed, so as to keep pregnant minks in middle and upper condition all the time. For example, a mink farm does not pay attention to feed allocation during pregnancy, broiler sausage and fat pork are still used during pregnancy, the feed is too fat, the nutrition is sufficient, the coat is bright, and the female mink is too fat. as a result, the pregnancy period is prolonged, the embryo is absorbed, and the litter size is reduced. generally, the litter size of female minks in the whole field is less than 6, most of which are 2-4, with an average litter size of 2.7, and a small number of female minks have smaller bellies and smaller fetuses in the later stage of pregnancy. In the end, none of them were born.

Pregnancy feed must control the amount of fat, each mink daily intake of fat should not exceed 8-12 grams. During pregnancy, it is strictly forbidden to use fatty feeds such as broiler sausage and fat pork to prevent minks from getting too fat during pregnancy.

5. Inbreeding. Some mink farms do not pay attention to breed renewal and excessive inbreeding, resulting in a reduction in litter size. If there is no exchange of male minks in a mink farm for 3 years, the inbreeding of the mink group is serious, resulting in a decrease in litter size, 3-5 litters, with an average litter size of 4. After the introduction of male mink in the following year, the same feeding and management method was adopted, and the average litter size was 5.5. Therefore, inbreeding should be avoided as far as possible.

6. The breeding method is improper. For example, in a mink farm, the female mink only mated once during the whole mating period and did not mate, resulting in a decrease in litter size, with an average litter size of 3.5. Mink is seasonal multiple estrus, stimulating ovulation animals, after mating and ovulation can accept mating and ovulation, so multiple mating can increase the conception rate and litter size. The mating methods of minks can be divided into two types: simultaneous mating and out-of-phase mating. The practice shows that the pregnancy rate and litter size are higher in different period than in the same period. In the production, the out-of-phase compound method is generally adopted, mainly using the different-phase compound mode of 1-7 or 1-7-1.