1, genetic factors

Inbreeding can lead to teratogenic and stillbirths. Sex chromosome abnormalities can cause infertility, even if the pregnancy is mostly deformed and stillbirth. Intrauterine environment should not be embryonic growth and development, manifested in the lack of hereditary lutein secretion, so that reduced or even lack of uterine milk, resulting in early embryonic death.

2, nutritional factors

(1) The lack of protein or essential amino acids in the feed of pregnant pigs can not meet the needs of pregnancy and can cause stillbirths, deformed fetuses, and weak babies.

(2) The lack of iodine in pregnant pigs can result in the death of early embryos, and mucinous edema occurs in piglets that are either absorbed by the mothers or are born prematurely or are born hairless.

(3) iron deficiency in pregnant pigs, increased stillbirth, weak fetus and similar policies fetus iron deficiency anemia, low disease resistance.

(4) β-carotene, not simply a precursor of vitamin A, can also promote the synthesis of progesterone in the ovary and reduce the death of early embryos. As an antioxidant, it prevents the transitional oxidation of fat, thereby protecting cholesterol synthesis in the uterus and ovaries from oxidative damage. Once there is a lack of feed, the amount of progesterone declines, and the lack of uterine milk increases the early embryonic mortality. The lack of vitamin A in pregnant sows can not only give birth to blinking piglets, but also can cause miscarriage, resulting in stillbirths, deformed fetuses, and weak litters.

(5) Vitamin E, also known as tocopherol, promotes the formation of sow egg cells, increases the vigor of the egg, facilitates the implantation, promotes the secretion of milk, can be transmitted to the suckling piglets through milk, and improves the antioxidation of suckling pigs. ability. At the same time, vitamin E can make the estrus smooth after the sow weaning. Therefore, 10 days before sow mating until delivery, to ensure that the vitamin E content of sow feed can not be less than 44ppm; can not be less than 48ppm during lactation. Otherwise, the above function will be weakened, and the degree of weakening is positively related to the lack of much. It will cause pan-examination, even if the estrus is mated and give birth. First, there will be fewer litters and more babies;

(6) Folic acid is a member of the vitamin B family, also known as vitamin BC or vitamin M. Widely found in yeast, green leafy vegetables, and animal liver and kidney tissues. It is one of the most important vitamins that affect sow breeding skills. Sows use 20 ppm. The gilts were started from the age of 9 weeks until they were bred. Adding 15 mg folic acid per Kg diet promoted the healthy development of the ovaries and uterus, and showed estrus, normal pregnancy, and over 10 litters. Sows supplemented with 5 mg of folic acid per Kg of diet can increase embryo survival by 7% for 35 days of gestation. Adding folic acid to pregnant sows, and increasing litter size by improving embryo viability, has been recognized by the pig industry. Once the supply of folic acid is insufficient, there may be a large number of dying and early embryonic deaths, as well as miscarriages, premature labor, stillbirths and mummified fetuses and weak litters.

(7) Biotin, also known as vitamin H, is a vitamin B family. Its main function is to increase the health of the hooves and prevent cropping, limp, and warts. At the same time can promote fetal growth and development and reduce fetal death and promote lactation plus more. If the content of biotin in the diet is lower than 330ug, it will cause stillbirth and suckling piglets to grow poorly due to insufficient breast milk.

(8) Niacin and Niacin, vitamin pp, are members of the Vitamin B family. Nicotinic acid is converted into nicotinamide in animals and participates in the redox process of metabolism in the body. In the absence of pregnant sows, there is a 30% increase in the risk of a soma syndrome in sows. The second is that suckling piglets are prone to exudative dermatitis and the mortality rate of piglets born within 7 days is high.

(9) The lack of vitamin B1, B2 choline and pantothenic acid (all vitamin B) can cause sows to produce stillbirths and weak ones.

3, environmental factors

(1) Heat stress. When the temperature was above 32°C, the return rate of sows was 19.7%.

(2) Air pollution, when ammonia, methane, hydrogen sulfide, and other toxic gases increase, sows can be abnormal estrus, mating after pregnancy, fewer litters, increased stillbirth.

(3) Toxins. In particular, the mycotoxins F2 and T2, which are found in the feed, can cause the sow to have false estrus. Even if the estrus is true and the breeding is difficult, the stillborn pigs will miscarry stillbirths.

(4) There are toxic chemicals, pesticides, gossypol poisoning, and sows suffering from heavier diseases that can cause miscarriage and stillbirth. In particular, reproductive disorders such as infertility and abortion caused by endometriosis and low birth weight (localized endometritis) have become one of the major diseases that cause non-infectious sows to reproduce.

4, some non-infectious factors

Non-infectious infertility in sows mainly includes delayed sows in young sows, estrus after weaning sows, non-pregnancy after mating, weak estrus, and ovarian cysts.

1) The delay of puberty

1 ovarian hypoplasia: multiple long-term suffering from chronic digestive diseases, chronic respiratory diseases, parasites, gilts. Due to incomplete ovarian development, there are no large follicles in the ovary to develop sufficient hormones to cause estrus.

When observing pigs for necropsy, it was found that the ovary was small and inelastic, and the surface was smooth without irregularities. Even if the follicular development is shaped like a grain of rice, the size of the soybean is not developed, and traces of past passing and passing eggs may not be found.

2 Insufficient stimulation of the opposite sex: In addition to the genetic factors, the early and late stages of the pig's primordial period are related to the timing of the gilts' initial exposure to the boar. Experiments have shown that when gilts reach 160-180 days of age, sexually mature boars can be stimulated directly, and the puberty can be advanced by about 30 days. At the same time, it has been proved that the stimulating effect of boars and sows in contact with sows for 1-2 hours per day is the same as the effect of continuous contact between boars and sows, and it is better to use different boars for multiple stimulations than to use the same boar for multiple stimulations.

3 improper feeding and management: gilts in the incubation period due to the nutritional level is too low or too high, resulting in sows body condition is too thin or too fat will affect the normal arrival of sexual maturity. Although some body conditions are normal, but in the early feeding, long-term lack of vitamin E, biotin and other nutrients in feed, gonadal development is inhibited, sexual maturity will be delayed. In addition, it is advisable to feed 4-6 heads per lap. Feeding 1 head in a single lap may have an adverse effect on the estrus of the sow. Overcrowding and frequent fighting can cause delays in the puberty.

4 Quiet estrus: Individual sows have reached sexual maturity, ovarian activity and follicular development are normal, but they do not show estrus symptoms or stand up reflexes in the presence of boars. This phenomenon is called quiet estrus or weak estrus. Weak estrus can take certain measures and sows can conceive.
There are obvious differences among varieties in this situation. The introduction of pig breeds and breeding pig breeds showed no obvious estrus performance, especially for gilts.

2) Sisters do not have heat (weakness) after weaning

1age parity: Under normal circumstances, 85%-90 sows showed estrus 7 days after weaning. Only 60-70% of gilts have estrus in the first week after the first delivery. This is the phenomenon that the second-born sows that are commonly performed in pig industry around the world are not estrus. The main reason for this phenomenon may be that the gilt body is still under development. According to body weight, it is not fully mature; gilts appear to be over-nurtured during the first lactation, and thus Director of Pig Uterus Recovery Process.

There is another problem that arises at the same time as this issue. This is the decrease in the number of litters in second-born sows. However, if hormones are used, this problem can be solved.

2 temperature and light:

High temperature: In the summer when the ambient temperature reaches 30°C or more, ovarian and estrus activity are suppressed. The weaning rate of adult sows in July, August and September was higher than that of weaning at other times, especially in young sows. These sows do not have estrus for more than a few days. Seasonal effects on the estrus of sows kept outside the house and in the house are obvious. Daily light for more than 12 hours has an inhibitory effect on estrus.

3 Size of herd: The estrus rate of adult sows reared alone after weaning was higher than that of herds reared in groups. The reason is that with the increase of herds, mutual biting each other increases the occurrence of hoof limb disease and mastopathy, and the effect of nutrient absorption becomes worse; boars and artificial observation of estrus have deteriorated.

4 The most common cause of irritability is lack of energy. For sows, the status at the time of breeding has a lot to do with feeding during lactation. Therefore, the weight loss of sows should be kept to a minimum during the lactation period, especially for gilts. One week after lactation, sows should take free food. During the hot summer season, the appetite of pigs must be guaranteed. Sows raised in groups need special care for individual thin sows.

5 Management factors: In terms of management, familiarize and master sow estrus identification technology. There are better breeding facilities.

3) No fetus after multiple breeding

The sow is estrus for more than 3 times and is still not pregnant. The incidence increased with the increase of the sow population. This type of pig accounts for 8 to 10% of the sows in the farm.

The reason for this is that the reason why the sow is not matched with the pregnancy is divided into two types depending on the timing of the sows mating or artificially granting the sperm and then returning to the heat.

Sows that estrus 21 days after mating belong to the estrus in the range of days of the normal cycle, indicating normal ovarian function. In this case, there are three reasons for the absence of a fetus after mating:

1 Fertility disorders. If uterine inflammation or uterine endometriosis hinder the movement and survival of sperm, sperm can not reach the site of fertilization; salpingitis or edema, embolism, and ovarian adhesions, etc., can cause fallopian tube atresia can not be fertilized.

2 Fertilized egg death: Early or late insemination of estrus, and use of semen that has been stored for a long period of time; or breeding of boars due to increased body temperature following heat stress, leading to early death of fertilized eggs;

3 Embryo died within 12 days of mating. That is, before the implantation of embryos floating in the uterus, the abnormal composition of common factors or suffering from high temperature, biting, transfer, transportation and excessive feed intake or mildew feed, etc., affect the embryos. The bed died quickly.

After mating with the estrus 25 days later, embryos died and were absorbed due to genital infection at the time of mating or postpartum. The utero embryos disappeared completely. Sows can again estrus. If fetal bones die, they can cause cadaverization and prolonged stagnation in the uterus, which can cause sows to lose their estrus.

Caused by the sow after mating is not due to the fetus, in addition to attention to sow aspects of bacterial infection, hormone secretion disorders and improper feeding and other factors, in the boar should be semen examination, especially in hot summer semen quality will appear temporary The decline in sex, and the conception rate has been severely affected.

4) Ovarian cysts

Etiology: Ovarian cysts are the most common diseases in swine ovary diseases. Ovaries can occur on one or both sides. Some vesicles can reach more than 5 cm in diameter. There are more than tens of vesicles, and some of them reach weight. 500 grams or more. Some pregnant sows also have 1-2 cysts. Follicular growth, development, maturation and depending on the balance of the pituitary FSH and LH. In particular, the balance between FSH and LH on ovulation is particularly important. If the balance is not reached and the amount of LH is reduced, ovulation does not occur and many follicular fluids accumulate in the follicles, causing the follicles to increase. Many cysts have a follicle diameter of more than 14 mm. One of the causes of ovarian cysts is the excessive secretion of thyrotropin.

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