CN117598241A - A method for improving the pregnancy and delivery rate of cloned recipient sows - Google Patents

Abstract

The invention relates to the technical field of mammalian reproduction, and specifically discloses a method for improving the pregnancy and delivery rate of cloned recipient sows. The method mainly includes: selection of recipient sows, sow estrus and detection, pre-embryo transfer management, embryo transfer surgery and post-operative care, pregnancy feeding, recipient sow farrowing, and birth care of cloned piglets. By supplementing the recipient sows with hormones and vitamin ADE injection before and after surgery, the pregnancy rate and farrowing rate of the recipient sows were improved; at the same time, supplementing N-carbamylglutamic acid during pregnancy increased the total number of recipient sows. The number of litters and the number of healthy piglets; at the same time, strict feeding amount management of sows during pregnancy is carried out to control the production weight of sows, thereby reducing the dystocia and stillbirth caused by underweight or overweight, and further improving the number of healthy piglets. number.

Description

Method for improving pregnancy labor rate of cloned recipient sow

Technical Field

The invention relates to the technical field of mammal reproduction, in particular to a method for improving pregnancy labor rate of cloned recipient sows.

Background

The somatic cell cloning technology refers to a technology of preparing cloned animals by performing inhibition culture on animal somatic cells to make the cells in a dormant state, adopting a nuclear transfer method, taking oocyte enucleation as a nuclear receptor, taking somatic cells or cell nuclei containing a small amount of cytoplasm as a nuclear donor, transferring the latter into the former to construct a recombinant embryo, reprogramming the donor nuclei in cytoplasm of the enucleated oocyte, starting cleavage, starting embryo development and gestation farrowing, and producing the cloned animals, which is also called somatic cell nuclear transfer technology. The somatic cell cloning technology can replicate excellent livestock, produce transgenic livestock, prepare animal disease model, isolate embryo stem cell, etc. and has great application value in agriculture and medicine. More than 20 mammals such as sheep, cattle, mice, pigs, rabbits, horses and the like have been successfully cloned at present, but the technology still has some unresolved problems, and the outstanding problem is that the birth efficiency of cloned animals is low, and most cloned embryos die in gestation. At present, the whole-period development efficiency of cloned embryos of pigs is only about 0.1-1%, and the popularization and application of somatic cell cloning technology in pig industry are seriously hindered by low cloning efficiency.

At present, the mainstream view points are that the abnormal development of cloned embryos is caused by the dedifferentiation, totipotency recovery and apparent genetic reprogramming abnormality in the process of starting embryo development, which are experienced by somatic cell genome in oocyte, so that the blastula rate is lower, but the latest researches show that even higher blastula rate can not obtain higher pregnancy delivery rate, so that the problem of lower pregnancy delivery rate of cloned embryos also needs more scientific discovery. In view of the current state of the art limitations, in vitro cloned embryos and in vitro fertilized embryos must be transferred to recipient sows to develop normally into complete individuals. How to ensure the normal implantation and development of the embryo is an important factor affecting the final efficiency of embryo transfer. Embryo implantation and development are closely related to the feeding management of recipient sows after embryo transfer, fat condition, physiological condition and embryo transfer.

In order to improve the pregnancy rate and the litter size of somatic cell clone embryo transfer, the number of transferred embryos is generally up to 200-300, and only about 20 embryos are needed for conception of common sows. The pregnancy rate of cloned embryo acceptor sow is generally 20-50%, the number of born is 2-6, and the whole cloning efficiency is 0.1-1%. Because the cloned embryo development is different from that of the common embryo, the corresponding breeding management measures such as recipient sow selection, sow hormone treatment, oestrus, embryo transfer preoperative management, embryo transfer operation and postoperative care, gestation feeding, recipient sow delivery, cloned piglet birth care and the like are different, so that better overall cloning efficiency is convenient to obtain.

Iron is one of important microelements in animal organism metabolism, and participates in physiological and biochemical processes such as electron transfer, oxidative phosphorylation and the like. Iron is also a component of ribonucleotide reductase and is involved in DNA synthesis in cells. Most of iron exists in the body in the form of hemoglobin, which is the main component of red blood cells and is the most important carrier for the body to transport oxygen and carbon dioxide. The hemoglobin content may reflect the body's iron steady state. Iron intake or absorption deficiency can lead to iron deficiency anemia characterized by decreased red blood cell count, decreased hemoglobin content, loss of appetite, drowsiness, increased respiratory rate, and severe anemia leading to death. The study shows that the sow hemoglobin level is in negative genetic correlation with the weight of the primary piglets and in positive genetic correlation with the survival rate of the piglets. Studies show that the hemoglobin content of pregnant sows is in negative linear correlation with reproductive performance. The iron content and biological potency of the feed material is low, and iron supplements are often added in commercial production to avoid iron deficiency.

The Chinese patent 201510261676.0 provides a method for improving the production performance of sows, which comprises daily management of gestation houses, gestation breeding, drug health care and conventional immunity in gestation, particularly the method for carrying out refined breeding management on gestation breeding and drug health care can obviously improve the survival rate and the healthy young rate of the sows, the survival rate reaches more than 98%, the average number of the sows is 12-14, the lactation capacity of the sows in the postnatal lactation period is high, the milk quality is high, the lactation peak period can be prolonged, the birth weight and the disease resistance of the newborn piglets are enhanced, and the method has great application prospect.

Chinese patent 201810465160.1 discloses a peptide chelated iron compound preparation for improving the production performance of sows and piglets, which is characterized by comprising the following components in percentage by mass: 15-25 parts of peptide chelated iron, 25-35 parts of probiotics and 10-15 parts of yeast cell wall. The invention has reasonable compatibility, shows a synergistic effect, not only can replace injection to supplement iron for piglets, but also can obviously increase milk yield of sows, improve feed utilization rate and immunity of sows and piglets, and has the advantages of increasing survival rate of piglets at birth, promoting animal growth, obviously improving productivity of sows and piglets, and the like.

At present, the iron supplement is divided into three types of inorganic salt iron, organic acid chelated iron and amino acid chelated iron, and the organic iron source in the prior art has limited effect in promoting the reproductive performance of sows, so that the research and development of the iron supplement with good digestion and absorption effects and high bioavailability has a certain market prospect in improving the pregnancy rate of cloned receptor sows.

Disclosure of Invention

In view of the above problems in the prior art, the technical problem to be solved by the present invention is to provide a method for improving pregnancy labor rate of cloned recipient sow.

The technical scheme of the invention is as follows:

a method of increasing pregnancy labor rate in a cloned recipient sow comprising the steps of:

s1, selecting a proper weaned sow or a nonpregnant sow as an alternative receptor sow according to a selection standard;

s2, when the candidate receptor sow is a weaned sow, intramuscular injection of Pregnant Mare Serum Gonadotropin (PMSG) and vitamin ADE injection is carried out on the second day of weaning, and Human Chorionic Gonadotrophin (HCG) is injected on the fourth day; when the candidate receptor sow is a nonpregnant sow, oral administration of allyl progestogen is carried out by mixing materials, the oral administration is carried out for 18 days, the injection of Pregnant Mare Serum Gonadotropin (PMSG) is carried out after the stop feeding for the second day, the injection of vitamin ADE is carried out, and the injection of Human Chorionic Gonadotropin (HCG) is carried out for the fourth day;

s3, backfat detection, oestrus detection and health condition detection are carried out on the sow which is an alternative receptor, embryo transplantation preoperative management is carried out on the sow which accords with the standard, and the number of the prepared sows is higher than the number of planned operations so as to be needed from time to time;

s4, intramuscular injection of cefquinome suspension into the qualified receptor sow, and uterine perfusion after mixing 10% lincomycin hydrochloride injection and houttuynia cordata injection, wherein vaginal purulent secretion is checked after 12 hours or 2 hours before operation, and the sow with purulent secretion cannot participate in transplantation;

s5, embryo transplantation operation is carried out on the recipient sow, strict disinfection measures are carried out, the environmental temperature and operation time are controlled, human Chorionic Gonadotrophin (HCG) is intramuscular injected after the operation is finished, and the Human Chorionic Gonadotrophin (HCG) is intramuscular injected again 14d after the operation is finished;

the recipient sow is intramuscular injected with ceftiofur sodium and cordate houttuynia every day three days after the S6 embryo is transplanted, and the wound is conventionally disinfected. And supplementing N-carbamylglutamic acid in the whole gestation period after operation, detecting backfat and feeding according to the detection result. The sow condition is checked every day after operation, including vaginal secretion and oestrus return and abortion, and B ultrasonic pregnancy is performed twice at 30d/60d after operation.

S7, performing body surface cleaning and disinfection on pregnant sows after embryo transplantation for 107-110d, entering a delivery house for delivery, intramuscularly injecting chloroprostaenol (PG) to hasten parturition on sows without delivery symptoms after the transplantation for 115d, performing caesarean delivery if no delivery symptoms exist after the sows exceed 118d, and performing birth recording and registration on cloned piglets after delivery;

and S8, carrying out birth care on the cloned piglets, sterilizing breasts of the sows, and then enabling the cloned piglets to independently take milk, if the cloned piglets cannot independently take milk, carrying out auxiliary milk, or carrying out artificial milk on the cloned piglets with birth defects, and carrying out health care and immunity on the cloned piglets according to a normal program. Further, the recipient sow in the step S1 is a long white pig, a big white pig and a binary hybrid pig.

Furthermore, the standard of the weaned sow selected in the step S1 is that the number of farrowing is more than 2, less than 45, the number of farrowing of two continuous fetuses is more than or equal to 12, the number of weaned pigs is more than or equal to 10, the upper fetuses are free from taking out, obvious uterine inflammation is avoided, the limb hooves are healthy, the breasts are normal, and the backfat is 14-18mm; the standard of the nonpregnant sow is the same as that of the weaned sow;

further, the injection amount of PMSG in the step S2 is 800-1000 iu/head, the vitamin ADE injection is 4-5 mL/head, and HCG is 400-500 iu/head.

Further, in the step S4, the dosage of the cefquinome suspension is-1 mL/20kg body weight, the dosage of the lincomycin hydrochloride injection is 10-20 mL/head, and the dosage of the cordate houttuynia injection is 50-60 mL/head.

Further, the HCG is used in the step S5 in an amount of 400-500 iu/head.

Further, in the step S6, the dosage of ceftiofur sodium is 0.5-1 g/head, and the dosage of houttuynia cordata injection is 20 mL/head.

Further, in the step S6, the supplementary amino acid is added with N-carbamylglutamic acid into the feed, the addition amount is 800-1000g/t, the addition amount of the organic iron chelating agent is 400-1000g/t, the supplementary vitamins are added with vitamin E, sodium selenite, biotin and folic acid into the feed, and the addition amounts are respectively 80-100g/t, 0.1-0.3g/t, 0.1-0.5g/t and 6-10g/t; postoperative management includes fasting on the first day, feeding 0.8-1 kg/head daily on the second day, feeding 1.2-1.5 kg/head on the third day, and feeding 1.6-2 kg/head on the fourth to tenth days.

Transfer of iron to the fetus by pregnant sows is partly achieved by uterine transferrin, a yellow leader protein secreted by the uterus, which is thought to be one cause of anemia in newborn piglets in the late gestation stage. Serum iron is the lowest in the late gestation period of the sow, and the fetal serum iron level tends to decrease during the gestation period at the time of the efficiency of transferring iron to the fetus, and the level of red blood cell packed plasma iron ions is positively correlated with fetal weight and placenta efficiency. Therefore, the farrowing rate of sows in gestation period and the survival rate of piglets are affected by iron. In the invention, the inventor prepares the iron complex and then complexes with mannose under alkaline condition to obtain the organic iron chelating agent, and the chelating agent has good water solubility, high absorptivity and stable structure, so that the chelating agent can be absorbed in intestinal tracts without being easily damaged, the utilization rate is greatly improved, the iron element can be fully absorbed in pregnant sows, the phenomena of anemia and the like can not occur when piglets are born, and the survival rate is higher. The invention also manages different feeding amounts of sows in gestation period so as to control the weight of the sows in production, thereby reducing the phenomena of difficult labor, stillbirth and the like caused by overweight or light weight and further improving the delivery rate.

The preparation method of the organic iron chelating agent comprises the following steps:

weighing 5-6 parts by weight of 2-aminomethylpyridine and 4-6 parts by weight of triethylamine, adding into 4-10 parts by weight of ethanol, adding 7-9 parts by weight of 3-bromopropionic acid, heating to 70-90 ℃, stirring for 20-30 hours, cooling to room temperature after the reaction is finished, filtering, washing residues with acetonitrile, and concentrating to dryness to obtain 3-pyridine-methylaminopropionic acid;

x2, weighing 2-3 parts by weight of 3-pyridine-methylaminopropionic acid and 2-3 parts by weight of tetramethylammonium hydroxide in the step X1, adding 10-20 parts by weight of methanol, adding 3-4 parts by weight of ferrous chloride tetrahydrate, stirring for 1-4 hours, filtering, pouring the filtrate into diethyl ether, precipitating, and filtering and drying after 7d to obtain an iron complex;

and X3, weighing 5-6 parts by weight of mannose oligomer, adding 25-30 parts by weight of water to dissolve the mannose oligomer, adding 0.5mol/L sodium hydroxide aqueous solution to adjust the pH to 9-10, stirring and uniformly mixing, keeping the pH to be 9-10 by 5-6 parts by weight of the iron complex in the step X2, adding two times of volume of absolute ethanol for ethanol precipitation, centrifuging at 4000-5000rpm for 5-10min, continuously centrifuging the lower precipitate after 2 times of volume of absolute ethanol precipitation, and freeze-drying the lower precipitate to obtain the mannose-iron complex serving as an organic iron chelating agent.

Further, in the step S6, the sow after the post-operation management is fed according to the backfat condition, specifically, the backfat is less than 14mm and is fed for 2.0-2.2kg/d after the operation for 11-30d, and the backfat is fed for 1.8-2kg/d for 14-18mm; 31-85d after operation, feeding back fat less than 14mm by 2.6-2.8kg/d, feeding back fat 14-18mm by 2.0-2.2kg/d, and feeding back fat more than 18mm by 1.8-2kg/d; after 86d of operation, backfat is 18-22mm and is fed by 2.8-3kg/d.

Compared with the prior art, the invention has the beneficial effects that:

(1) Due to the large number of embryos transferred into the recipient sow, insufficient hormone in the recipient sow can affect cloned embryo development and implantation conception. Therefore, hormone is additionally supplemented before and after transplantation, so that the level of hormone in the recipient sow can be maintained, an intrauterine environment which is favorable for embryo development and implantation is provided, and the pregnancy rate is further improved;

(2) After recipient sow transplantation, the main factor affecting litter size and healthy litter size is high embryo loss rate in gestation period of the sow. Therefore, the inventor supplements N-acetylglutamic acid (NCG) in gestation period, can promote endogenous arginine synthesis, and can effectively improve litter size and healthy number of sows. Simultaneously, vitamins are supplemented to promote the uterine dilatation and placenta formation in gestation, increase the uterine horn length and the placenta surface area, better provide nutrition for the fetus and promote the growth and development of the fetus;

(3) In the gestation period feeding management of pregnant sows, the effect of adjusting the feeding amount according to the backfat condition is that: if the gestation period is too thin, nutrition supply of the fetus is affected, so that weak or malformed fetus and dead fetus are increased; too thin can also lead to insufficient physical energy storage of the sow, so that the sow is powerless in farrowing, difficult in production and even choking death of the fetal pig; the overfeeding of the sow can also lead to the increase of difficult yield of the prolongation of the birth process due to the overfeeding of the fetus and the narrow birth canal, so the feeding amount is timely adjusted according to the backfat, and the difficult yield of the pregnant receptor sow can be greatly reduced by keeping the moderate fat condition.

Detailed Description

The technical scheme of the present invention will be described in detail by means of specific examples, which should be explicitly set forth for illustration, but should not be construed as limiting the scope of the present invention.

The parameters of partial raw materials in the embodiment of the invention are as follows:

example 1

A method of increasing pregnancy labor rate in a cloned recipient sow comprising the steps of:

s1, selecting 15 sows from weaned white sows to give birth more than 2, 5 or less, wherein the number of continuous two farrowes is more than 12, and the number of weaned piglets is more than 10, and the sows with upper fetuses without taking out birth, obvious uterine inflammation, healthy limb and hooves, normal breasts and backfat of 14-18mm are used as candidate receptor sows;

s2, injecting PMSG1000iu and vitamin ADE injection into each muscle of the weaning sow of the 2 nd day of the recipient, and injecting HCG500iu of the 4 th day;

s3, backfat detection is carried out on the recipient sow, the backfat thickness is 15-22mm, estrus and physical condition detection is carried out on the recipient sow, and embryo transplantation preoperative management is carried out on qualified sows;

s4, injecting cefquinome suspension into 10 heads of the qualified recipient sow according to the weight of 1mL/20kg, simultaneously using 20mL of 10% lincomycin hydrochloride injection and 60mL of cordate houttuynia injection for each sow, and then pouring into the uterus, wherein vaginal purulent secretion is checked after 12 hours or 2 hours before operation, and the sow with purulent secretion cannot participate in transplantation;

s5, embryo transplantation operation is carried out on the recipient sow, the environment and operation time are strictly disinfected, the HCG500iu is intramuscular injected into each sow after the operation is finished, and the HCG500iu is intramuscular injected again 14d after the operation is finished;

the recipient sow is intramuscular injected with ceftiofur sodium 1 g/head+cordate houttuynia 20 mL/head every day three consecutive days after the S6 embryo transfer, and the wound is conventionally disinfected. The above-mentioned supplement is added into conventional feed to feed the receptor sow according to 800g/t of N-carbamylglutamic acid, 1000g/t of organic iron chelating agent, 100g/t of vitamin E, 0.3g/t of sodium selenite, 0.5g/t of biotin and 10g/t of folic acid in the whole gestation period after operation. Specific postoperative feeding management includes: fasted on the first day, fed 1 kg/head on the second day, 1.5 kg/head on the third day, 2 kg/head per day on the fourth to tenth days; and supplementing N-carbamylglutamic acid in the whole gestation period after operation, detecting backfat and feeding according to the detection result. Feeding back fat of less than 14mm for 2.2kg/d after operation for 11-30d, and feeding back fat of 14-18mm for 2kg/d; 31-85d after operation, feeding back fat less than 14mm for 2.8kg/d, feeding back fat 14-18mm for 2.2kg/d, and feeding back fat more than 18mm for 2kg/d; after 86d of operation, backfat is 18-22mm, and 3kg/d is fed; the sow condition is checked every day, including vaginal secretion and oestrus return, and B ultrasonic pregnancy is performed twice at 30d/60d after operation.

S7, cleaning and sterilizing pregnant sows after embryo transplantation for 110d, entering a delivery house for delivery, carrying out intramuscular injection of chloroprostenol 2mL for induced delivery of the sows without delivery symptoms after transplantation for 115d, carrying out caesarean delivery if no delivery symptom exists in more than 118 days, and carrying out birth recording and registration on cloned piglets after delivery;

and S8, carrying out birth care on the cloned piglets, sterilizing breasts of the sows, enabling the piglets to take milk autonomously, assisting in lactation if the cloned piglets cannot self-feed, or carrying out artificial lactation on the cloned piglets with birth defects, and carrying out health care and immunity on the cloned piglets according to a normal program.

The preparation method of the organic iron chelating agent comprises the following steps:

x1, weighing 540g of 2-aminomethylpyridine and 505g of triethylamine, adding into 5L of absolute ethyl alcohol, adding 765g of 3-bromopropionic acid, heating to 80 ℃, stirring for 24 hours, cooling to room temperature after the reaction is finished, filtering, washing residues with acetonitrile, and concentrating to dryness at 45 ℃ and minus 0.9MPa to obtain 3-pyridine-methylaminopropionic acid;

x2, weighing 250g of 3-pyridine-methylaminopropionic acid and 250g of tetramethyl ammonium hydroxide in the step X1, adding into 10L of methanol, adding 375g of ferrous chloride tetrahydrate, stirring for 3 hours, filtering, pouring the filtrate into diethyl ether, precipitating, filtering after 7d, and drying at 40 ℃ for 8 hours to obtain an iron complex;

and X3, weighing 600g of mannose oligomer, adding into 3L of water, uniformly mixing, adding 0.5mol/L sodium hydroxide aqueous solution to adjust the pH to 10, stirring and uniformly mixing, adding 600g of the iron complex obtained in the step X2, keeping the pH at 10, adding two times of volume of absolute ethyl alcohol for alcohol precipitation, centrifuging at 4500rpm for 10min, centrifuging the lower precipitate continuously for 10min after 2 times of volume of absolute ethyl alcohol precipitation, and lyophilizing the lower precipitate at-30 ℃ for 48h at 9Pa to obtain the mannose-iron complex serving as the organic iron chelating agent.

The experiment was divided into 3 batches of 10 sows each, and 30 sows were treated in total.

Example 2

The only difference from example 1 is that the organic iron chelator is replaced with ferrous glycine chelate in the gestational feed.

Example 3

The difference from example 1 is only that the feed amount of each recipient sow during gestation, i.e. post-operative management in step S6, is 3kg/d.

Example 4

The difference as in example 1 is only that no additional supplementation of N-carbamylglutamic acid is carried out in the feed during gestation.

Comparative example 1

The only difference with example 1 is that no additional supplementation of the organic iron chelator is made in the gestational feed.

Test example 1

The postpartum sow was counted according to the methods of each control and example, including pregnancy rate, farrowing rate, total litter size, healthy litter size, and piglets with birth weight >900g, and the specific results are shown in table 1.

Table 1 comparative analysis of sow farrowing rates by different treatments

Group of

Number of heads

Pregnancy with a new device

Pregnancy rate

Delivery of childbirth

Labor rate

Litter size

Number of healthy litters

Comparative example 1

30

10

33.33％

8

26.67％

4.5±0.93

3.5±0.54

Example 1

30

22

73.33％

18

60％

6.5±1.5

5.4±1.1

Example 2

30

20

66.67％

15

50％

5.2±0.77

4.07±0.8

Example 3

30

12

40％

10

33.33％

5.8±0.92

5.2±0.79

Example 4

30

11

36.67％

9

30％

5.3±0.64

4.94±0.68

From the standpoint of sow delivery and piglet survival, it is seen that additional nutritional supplements are necessary to the sow during gestation. N-carbamylglutamic acid is a structural analogue of N-acetylglutamic acid, can promote endogenous synthesis of arginine, and arginine is metabolized in a body to generate Nitric Oxide (NO) and polyamine, so that NO can relax smooth muscle, promote capillary generation and formation, increase microcirculation of the body, improve reproductive performance of multiple fetal animals, and effectively improve litter size and birth weight of sows, so that effective litter size and survival rate of piglets of sows supplemented with N-carbamylglutamic acid are higher. The oligomannose contains many chemical bonds which are not hydrolyzed by amylase, and its structural properties and the like are not easily changed, so that it is not only resistant to hydrolysis by saliva or hydrolysis by gastric and pancreatic secretions, but also they are not absorbed or degraded in the small intestine. When the iron ions and mannose are chelated to form a stable complex, a stable chemical bond structure is formed, and the complex is not influenced by other substances, so that intestinal tracts can be smoothly reached, and the absorption rate of iron elements is improved. The intake effect of the iron element directly influences the content of hemoglobin in the pregnant sow and is also directly related to the primary weight of the piglets, so that the sow delivery rate without additionally supplementing the iron element can be seen to be poor, and the survival situation of the piglets is finally poor. However, in example 3, the sow is lean or overfertilized due to the lack of the feeding amount distinction of the pregnant sow, which is not beneficial to pregnancy and delivery, but also leads to dystocia, so that the delivery rate of the sow and the survival condition of the piglet are not ideal.

Claims (10)

1. A method for improving the pregnancy and delivery rate of cloned recipient sows, which is characterized in that it includes the following steps: S1 selects suitable weaned sows or pregnant sows as candidate recipient sows based on the selection criteria; S2 When the candidate recipient sow is a weaned sow, pregnant mare serum gonadotropin and vitamin ADE injection are intramuscularly injected on the second day after weaning, and human chorionic gonadotropin is injected on the fourth day; When the sows are empty-pregnant, allylenogest is taken orally through the mixture for 18 consecutive days. On the second day after feeding is stopped, pregnant horse serum gonadotropin and vitamin ADE injection are injected. On the fourth day, human chorionic gonadotropin is injected. hormone; S3 conducts backfat test, estrus test and health test on the candidate recipient sows. Sows that meet the standards are managed before embryo transplantation. The number of sows prepared should be higher than the number of planned surgeries in case of emergency; Recipient sows that passed the S4 inspection were intramuscularly injected with cefquinoxime suspension, and mixed with 10% lincomycin hydrochloride injection and Houttuynia cordata injection for uterine perfusion. The vagina was inspected 12 hours after uterine perfusion or 2 hours before surgery. Purulent secretions, sows with purulent secretions cannot participate in transplantation; S5 performs embryo transfer surgery on recipient sows, strictly disinfects the environment, controls the environmental temperature and the operation time. Human chorionic gonadotropin is injected intramuscularly after the operation, and human chorionic gonadotropin is injected intramuscularly 14 days after the operation. After S6 embryo transplantation, the recipient sows were given intramuscular injections of ceftiofur sodium and Houttuynia cordata every day for three consecutive days, and the wounds were routinely disinfected. After surgery, N-carbamylglutamic acid, amino acids, organic iron chelators, and vitamins were supplemented throughout pregnancy. Backfat testing was performed and feeding was performed based on the test results. Check the condition of the sow every day after the operation, including vaginal secretions, return to estrus, and abortion, and do two B-ultrasound pregnancy tests on the 30th day/60th day after the operation; S7 pregnant sows undergo body surface cleaning and disinfection 107-110 days after embryo transplantation, and then enter the farrowing house to wait for delivery. Sows with no symptoms of labor 115 days after transplantation can be intramuscularly injected with cloprostenol to induce labor. If there are still no signs of labor after 118 days, sows will be After caesarean section, birth records and registration of cloned piglets will be carried out after delivery; S8 provides birth care to the cloned piglets. After disinfecting the sow's udder, the cloned piglets are allowed to breastfeed on their own. If the cloned piglets cannot breastfeed autonomously, they will be assisted to breastfeed. Or if the cloned piglets have birth defects, they will be artificially breastfed. The cloned piglets will be treated according to normal procedures. Carry out health care and immunity. 2. The method according to claim 1, characterized in that: in step S1, the recipient sow breeds are Landrace pigs, Large White pigs and binary hybrid pigs, and it is prohibited to select ternary sows. 3. The method according to claim 1, characterized in that: the standards for the weaned sows selected in step S1 are more than 2 births and less than 5 births, the number of piglets born in two consecutive births is ≥ 12, and the number of weaned piglets is ≥ 10 pigs, no farrowing, no obvious uterine inflammation, healthy limbs and hooves, normal breasts, and 14-18mm back fat; the standards for empty-pregnant sows are the same as those for weaned sows. 4. The method according to claim 1, characterized in that: the injection volume of pregnant horse serum gonadotropin in step S2 is 800-1000iu/head, the vitamin ADE injection is 4-5mL/head, and the human chorionic villus Gonadotropin is 400-500iu/head. 5. The method according to claim 1, characterized in that: the dosage of cefquinoxime suspension in step S4 is 1mL/20kg body weight, and the dosage of lincomycin hydrochloride injection is 10-20mL/head, The dosage of Houttuynia cordata injection is 50-60mL/head. 6. The method of claim 1, wherein the dosage of human chorionic gonadotropin in step S5 is 400-500iu/head. 7. The method according to claim 1, characterized in that: in step S6, the dosage of ceftiofur sodium is 0.5-1g/head, and the dosage of Houttuynia cordata injection is 20 mL/head. 8. The method of claim 1, characterized in that: supplementing amino acids in step S6 is adding N-carbamylglutamic acid in the feed, and the addition amount is 8000g/t; postoperative management includes the first day After fasting, feed 0.8-1kg/head every day on the second day, 1.2-1.5kg/head on the third day, and 1.6-2kg/head on the fourth to tenth day. 9. The method of claim 1, characterized in that: the preparation method of the organic iron chelating agent includes the following steps: X1 Add 2-aminomethylpyridine and triethylamine to ethanol, then add 3-bromopropionic acid, heat to 70~90°C and stir for 20~30h. After the reaction is completed, cool to room temperature, filter, and the residue is treated with acetonitrile After washing, concentrate to dryness to obtain 3-pyridine-methylaminopropionic acid; X2 Take 3-pyridine-methylaminopropionic acid and tetramethylammonium hydroxide in step Precipitation appeared after treatment, and after 7 days, it was filtered and dried to obtain the iron complex; In Add twice the volume of absolute ethanol for ethanol separation, and centrifuge. The lower precipitate is separated by ethanol with 2 times the volume of absolute ethanol and then centrifuged again. The lower precipitate is freeze-dried to obtain a mannose-iron complex as an organic iron chelator. 10. The method according to claim 1, characterized in that: in step S6, the sows after the postoperative management are fed according to the backfat condition, specifically 11-30 days after the operation, the backfat is less than 14mm. Feed 2.0-2.2kg/d, backfat 14-18mm feed 1.8-2kg/d; 31-85 days after surgery, backfat <14mm feed 2.6-2.8kg/d, backfat 14-18mm feed 2.0-2.2 kg/d, backfat>18mm, feeding 1.8-2kg/d; after 86 days after surgery, backfat 18-22mm, feeding 2.8-3kg/d.