A timed insemination method for gilts to optimize hormone usage patterns

Abstract

The invention discloses a method for timed insemination of gilts for optimizing hormone usage patterns, comprising: 1) selecting gilts: selecting gilts in estrus, wherein the estrus span of the selected gilt group is within 11 days; 2) performing synchronization treatment: feeding alkaloids to gilts that are in estrus on the 1st, 2nd, 3rd, 4th, 5th and 6th days respectively starting from the 16th day after estrus, and continuously feeding them for 12, 11th, 10th, 9th, 8th and 7th days respectively; and feeding alkaloids to gilts that are in estrus on the 7th, 8th, 9th, 10th and 11th days respectively starting from the 15th, 14th, 13th, 12th and 11th days after estrus, and continuously feeding them for 7 days; 3) performing superovulation; and 4) artificial insemination. The present invention reduces the treatment time of progesterone hormones, reduces the usage amount of progesterone hormones, reduces the application cost and the return to estrus ratio, and improves the reproductive traits of gilts such as the first-time breeding conception rate, the first-time weaning estrus rate, and the average number of piglets born in the second litter.

Description

Technical Field

[0001] The present invention relates to the technical field of livestock breeding, and in particular to a method for timed insemination of gilts for optimizing hormone use patterns. Background Art

[0002] The reproductive performance of gilts in pig farming is a key factor in ensuring stable production and maximizing profits. The optimal replacement number of gilts in production should be maintained between 20% and 30% of the base sow herd. However, because 10% to 30% of gilts experience latent estrus or no estrus, conventional gilt herds frequently experience uneven estrus and low breeding rates. In recent years, with the significant advancements in scale and intensification of the pig farming industry, many farms have begun using timed insemination technology in gilt breeding to facilitate full-in, full-out batch production, reduce labor costs, improve production efficiency, and minimize the risk of cross-infection. Timed insemination technology uses progesterone analogs to synchronize the gilt's ovarian cycle, followed by the use of gonadotropins to synchronize estrus and ovulation, ultimately allowing for simultaneous breeding of the gilts. With the promotion and application of this technology in actual production, the first-time breeding concentration and farrowing concentration of gilts have been significantly improved.

[0003] Currently, the timed insemination technique for gilts requires feeding 20 mg / gilt / day of allylprogesterone (an oral active progestogen) for 18 consecutive days. This inhibits gonadotropin secretion, thereby suppressing follicular development, adjusting the ovarian cycle, and synchronizing the estrus cycle. This is followed by an injection of pregnant mare serum gonadotropin (PMSG) (1000 IU / gilt) to promote follicular development and induce estrus. Gonadotropin-releasing hormone (GnRH) (100 μg / gilt) is then injected to accelerate the final maturation of the dominant follicle and the release of the egg. Finally, artificial insemination is performed uniformly at a pre-set time. Clearly, the current timed insemination technique uses a large dose of allylprogesterone for ovarian cycle synchronization, requiring a long treatment time. This results in prolonged, high-dose hormone stimulation of the ovaries, disrupting the normal ovarian cycle and follicular development potential of the gilts, while also increasing the cost of the technique. Therefore, the current timed insemination technology for gilts still has the following problems that need further improvement: (1) The amount of hormones used is too large, the cost is high, and the side effects are large; (2) The breeding conception rate of gilts has not been significantly improved; (3) The average litter size has not been significantly improved; (4) The weaning estrus rate of gilts has not been significantly improved.

[0004] Therefore, we need to find an optimized solution to reduce the dosage of allylgestalone treatment during the timed insemination process of gilts. By effectively reducing the dosage of hormones in the synchronization treatment, we can improve the reproductive traits of gilts such as conception rate, weaning estrus rate and average litter size, and effectively reduce the application cost of timed insemination technology, so as to achieve the optimization and improvement of the current timed insemination technology for gilts. Summary of the Invention

[0005] In response to the problems existing in the existing timed insemination technology for gilts, the present invention provides a timed insemination method for gilts that optimizes the hormone usage pattern, with the aim of reducing the use of allylgestalone and lowering processing costs, while improving the reproductive performance of gilts and tapping the reproductive potential of gilts, thereby increasing the value of implementing the timed insemination technology for gilts.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for timed insemination of gilts with optimized hormone usage pattern comprises the following steps:

[0008] 1) Selecting gilts: Select gilts in estrus, and the estrus span of the selected gilt group should be within 11 days;

[0009] 2) Synchronization treatment: For gilts that come into estrus on the 1st, 2nd, 3rd, 4th, 5th and 6th days, they will be fed with allylgestalone starting on the 16th day after coming into estrus, and will be fed continuously for 12, 11th, 10th, 9th, 8th and 7th days respectively; for gilts that come into estrus on the 7th, 8th, 9th, 10th and 11th days, they will be fed with allylgestalone starting on the 15th, 14th, 13th, 12th and 11th days after coming into estrus, and will be fed continuously for 7 days respectively;

[0010] 3) Implement superovulation;

[0011] 4) Artificial insemination.

[0012] Furthermore, step 1) selects estrus gilts over 210 days old.

[0013] Furthermore, in step 2), the feeding amount of alprogesterone in the synchronization treatment is 20 mg / head / day.

[0014] Furthermore, the specific operation of superovulation in step 3) is as follows: 1000 IU PMSG / gilt is intramuscularly injected 42 hours after stopping feeding alprogesterone, and 100 μg GnRH / gilt is intramuscularly injected 80 hours after intramuscular injection of PMSG.

[0015] Furthermore, the specific operation of step 4) artificial insemination is as follows: the first artificial insemination is performed 24 hours after the intramuscular injection of GnRH, and the second artificial insemination is performed 16 hours after the first artificial insemination.

[0016] Beneficial effects of the present invention:

[0017] 1. The mechanism of the timed insemination technology for gilts is to use exogenous hormones to artificially control and adjust the estrus process of the gilt group, so that the entire gilt group can achieve synchronized estrus, synchronized ovulation, synchronized breeding, and synchronized parturition. However, the timed insemination technology currently implemented uses a unified pattern of hormone stimulation when treating gilt groups, ignoring the fact that the sensitivity and tolerance of the gilt ovaries to reproductive hormones are different at different physiological stages. First, different ovarian cycles may have different sensitivities to progesterone hormones, which will lead to differences in the speed and quality of follicle recruitment in different ovarian cycles, resulting in uneven follicle development or the failure to develop qualified follicles. Secondly, large doses and long-term progesterone hormone stimulation may inhibit the development of pre-antral follicles in the ovaries, leading to difficulties in subsequent follicle recruitment and development. To address the problems existing in the current timed insemination technology for gilts, the present invention initiates the synchronization treatment of gilts from the late luteal phase to the early follicular phase of the ovarian cycle. By reducing the treatment time of progesterone hormones and the amount of progesterone hormones used, the application cost of the timed insemination technology for gilts and the return to estrus rate after mating are reduced, and the reproductive traits of gilts such as the first-time mating conception rate, the first-time weaning estrus rate, and the average number of piglets born in the second litter are improved, thereby achieving efficient utilization of gilts. Specifically,

[0018] (1) Different from the conventional 18-day allylgestaltenes synchronization treatment, the embodiment of the present invention selects estrus gilts for 11 consecutive days to ensure that the estrus span of the selected gilts is within 11 days, and starts the allylgestaltenes synchronization treatment on the 11th to 16th day after estrus, controlling the treatment time of allylgestaltenes for gilts to 7-12 days, thereby greatly reducing the hormone treatment time and hormone usage of gilts.

[0019] (2) In the embodiment of the present invention, the total time of allylprogesterone treatment in the synchronous treatment of 25 gilts was reduced from 450 days to 225.67 days, the total amount of allylprogesterone used was reduced from 2250 ml to 1125 ml, and the unit cost of the synchronous treatment of gilts was reduced from 52 yuan to 26 yuan. The hormone treatment time, usage and unit cost were all reduced by about 50%.

[0020] (3) Compared with the current conventional 18-day allylprogesterone synchronous treatment timed insemination technology, the timed insemination technology with optimized hormone use pattern in the embodiment of the present invention reduces the return to estrus rate of primiparous gilts from 22.67% to 14.67%; increases the first-parity conception rate of gilts from 74.67% to 81.33%; increases the first-parity weaning estrus rate of gilts from 85.64% to 98.13%; and increases the average number of piglets born in the second litter of gilts from 12.20 to 13.04.

[0021] 2. In the process of my country's pig farming gradually transforming to large-scale intensive production, batch production plays an important role. Pig farms use batch production to reasonably divide batches according to the size of the sow group, and have reasonable intervals between batches, so that the pig group can enter and exit as a whole, the entire pig house can be disinfected, and the frequency of staff contact with the pig group can be reduced, effectively blocking the path of disease transmission and reducing cross-infection of diseases, especially in the prevention and control of major infectious diseases such as "African swine fever". The timed insemination technology for reserve sows is a key technology for carrying out batch production of pigs. The present invention optimizes the use pattern of hormones, reduces the use of hormones in batch production of pig farms, and reduces the cost of technology application. It not only improves the reproductive performance of reserve sows in their first birth, but also significantly improves the reproductive performance of reserve sows in their second birth. The application of this technology can create greater economic value for batch production in pig farms. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the grouping of gilts.

[0023] Figure 2 Flow chart of the technical operation of timed insemination for gilts. DETAILED DESCRIPTION

[0024] The present invention will be further explained below in conjunction with the examples and drawings. The following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0025] The current scheduled insemination procedure for gilts does not take into account the ovarian physiological cycle. Gilts are randomly selected and then artificially inseminated over a 23-day period, with 18 days of synchronization. The use of high doses of hormones during this period not only increases the application cost of the technology but also affects the reproductive potential of gilts, causing reproductive problems in their second parity. This manifests itself in low conception rates, low litter sizes, low weaning estrus rates, and low litter sizes in second-parity gilts. Currently, reducing costs, reducing hormone usage, improving estrus breeding efficiency, and scientifically tapping into reproductive potential in the implementation of scheduled insemination technology for gilts has become an urgent issue.

[0026] To effectively reduce the use of synchronizing hormones, it is necessary to identify steps within the timed insemination protocol that can be optimized based on the characteristics of follicular development. Compared to the luteal phase, timed insemination during the follicular phase significantly increases the transcriptional levels of LHCGR and CYP19A1 in the follicular wall of gilts, while simultaneously decreasing CYP11A1 transcription. This is likely due to differences in sensitivity and tolerance to reproductive hormone stimulation during different phases of the ovarian cycle. Upregulated LHCGR expression in normal follicles plays a crucial role in follicular development, estrogen synthesis, and ovulation, while upregulated CYP19A1 expression effectively inhibits apoptosis in porcine ovarian granulosa cells and promotes E2 synthesis. However, in abnormal follicles, CYP19A1 expression is downregulated during follicular atresia, and CYP11A1 is abnormally expressed in the follicle membrane of polycystic ovary syndrome (PCOS). Therefore, we confirm that timed insemination during the follicular phase of gilts is more conducive to normal follicular development. Taking this as a starting point to optimize the synchronization steps in the timed insemination procedure, it is possible to achieve a double increase in the breeding conception rate and postpartum estrus breeding rate of reserve sows on the basis of reducing the amount of hormones used.

[0027] In response to the problems that arise in the current timed insemination technology for gilts, the present invention provides a timed insemination technology for gilts that optimizes the hormone usage pattern. This technology implements a short-term synchronization treatment on gilts from the late luteal phase to the early follicular phase of the ovarian cycle. Combined with superovulation (PMSG+GnRH) and artificial insemination, it can also enable gilts to achieve the goals of synchronized estrus, synchronized ovulation, synchronized breeding, and synchronized parturition. This technology not only avoids the gilts from being stimulated by long-term, large doses of progesterone during the synchronization process, but also effectively reduces the application cost and return rate of the timed insemination technology for gilts, and also increases the primiparous breeding conception rate, the primiparous weaning estrus rate, and the average number of piglets born in the second litter. Therefore, the present invention effectively solves the shortcomings of the existing technology and improves the economic benefits of the application of timed insemination technology for gilts.

[0028] Example 1

[0029] 1 Experimental animals

[0030] The control group consisted of 25 randomly selected large gilts aged 210 days or older. The optimized hormone administration group (hereinafter referred to as the optimized group) consisted of 25 gilts in estrus, selected from a group of large gilts aged 210 days or older, after 11 consecutive days of estrus monitoring. Prior to the start of the experiment, the animals were fed juice via a feeder for three days to induce feeding habits and allow them to adapt to the feeder administration method. The experiment was repeated three times.

[0031] 2 Experimental group design and technical operation process

[0032] 2.1 Experimental group design

[0033] The control group: According to the current technical requirements for timed insemination of gilts, they were first treated with progesterone for 18 days, then superovulated with PMSG and GnRH, and finally artificial insemination;

[0034] Optimization group: In the order from near to far from the estrus date, the synchronization treatment of allylgestaltenes was started on the 11th to 16th day after the estrus of the gilts, and the current 18-day synchronization treatment time was reduced to 7-12 days. The rest of the treatment steps were the same as the control group.

[0035] The specific operations of the optimization group synchronization process are as follows (such as Figure 1 shown):

[0036] The selection of replacement gilts was as follows: gilts in estrus were selected for synchronization, requiring the estrus span of the experimental pig group to be within 11 days, and the estrus sows were marked as gilts in estrus on days 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 according to the order of estrus;

[0037] The start time of synchronization treatment is as follows: for gilts that come into estrus on days 1-6, synchronization treatment starts on day 16 after their estrus; for gilts that come into estrus on days 7, 8, 9, 10, and 11, synchronization treatment starts on days 15, 14, 13, 12, and 11 after their estrus, respectively. In this optimization technology, the start time of synchronization treatment needs to be at least 10 days after the estrus day.

[0038] The end time of synchronization treatment is as follows: for gilts that are in estrus on the 7th to 11th day, 7 days of synchronization treatment will be implemented; for gilts that are in estrus on the 1st to 6th day, the end time of synchronization treatment will be based on the end time of gilts that are in estrus on the 7th to 11th day, and will end uniformly, that is, 12, 11, 10, 9, 8, and 7 days of synchronization treatment will be implemented respectively.

[0039] 2.2 Technical Operation Process

[0040] The control group was fed alprogesterone daily at 3:00 PM, with the first day of alprogesterone feeding designated as Day 1. Alprogesterone was then fed continuously for 18 days at a rate of 20 mg / head / day. Forty-two hours after stopping alprogesterone, each head received an intramuscular injection of 1000 IU PMSG. Eighty hours after the intramuscular injection of PMSG, 100 μg / head of GnRH was administered intramuscularly. The first artificial insemination (AI) was performed 24 hours after the intramuscular injection of GnRH, and the second AI was performed 16 hours after the first AI. Subsequently, the animals were monitored for return to estrus, conception, farrowing, estrus at weaning, and the birth of a second litter (the second litter was bred using a combination of natural estrus after weaning and artificial insemination).

[0041] Optimization group: Gilts that came into estrus on days 1, 2, 3, 4, 5, and 6 were fed alprogesterone starting at 3 p.m. on the 16th day after estrus, and continued to be fed for 12, 11, 10, 9, 8, and 7 days, respectively, at 20 mg / head / day; gilts that came into estrus on days 7, 8, 9, 10, and 11 were fed alprogesterone starting at 3 p.m. on the 15th, 14th, 13th, 12th, and 11th days after estrus, and continued to be fed for 7 days, at 20 mg / head / day. All gilts were treated with the same treatment (feeding alprogesterone) for 7-12 days and then stopped the drug. 42 hours after stopping alprogesterone, each gilt was injected intramuscularly with 1000 IU PMSG; 80 hours after intramuscular injection of PMSG, GnRH was injected intramuscularly at 100 μg / head. The first artificial insemination (AI) was performed 24 hours after intramuscular injection of GnRH, and the second artificial insemination (AI) was performed 16 hours after the first artificial insemination. The subsequent return to estrus, conception, farrowing, weaning estrus, and second litter births were then tracked (the second litter breeding program used a combination of natural estrus after weaning and artificial insemination). The operation process is shown in Figure 2 .

[0042] 3 Experimental data collection

[0043] 3.1 Cost of synchronous treatment of gilts in the control group

[0044] 3.1.1 Total amount of allylgestalone used in the synchronous treatment of 25 gilts in the control group:

[0045] All gilts in the control group were subjected to 18-day synchronization treatment. Each gilt was fed 5 ml (20 mg) of allylprogesterone per day for 18 consecutive days. The total amount of allylprogesterone used in the synchronization treatment of the 25 gilts was 5 ml / day / head × 18 days × 25 heads = 2250 ml.

[0046] 3.1.2 Unit cost of the synchronous treatment of 25 gilts in the control group:

[0047] Taking allylgestalen (450ml / bottle) with a market price of 260 yuan / bottle as an example, the unit cost of the synchronous treatment of 25 gilts in the control group is M = 2250ml ÷ 450ml / bottle × 260 yuan / bottle ÷ 25 heads = 52 yuan.

[0048] 3.2 Optimizing the cost of synchronous treatment of gilts within the group

[0049] 3.2.1 Optimize the total amount of allylgestalone used in the synchronization treatment of the 25 gilts in the group:

[0050] The treatment time and amount of alprogesterone used in the synchronization treatment of gilts in the optimization group are not uniform and will vary with the different estrus time of the gilts. Each gilt needs to be calculated separately. The calculation of the treatment time and total amount of alprogesterone used in the synchronization treatment is as follows:

[0051] Each gilt was fed 5 ml (20 mg) of allylgestaltenes per day. The total number of days of allylgestaltenes treatment in the synchronous treatment of 25 gilts in the optimization group was T = N1 × 12 days + N2 × 11 days + N3 × 10 days + N4 × 9 days + N5 × 8 days + N 6-11 × 7 days (N1, N2, N3, N4, N5 represent the number of gilts in estrus on the 1st, 2nd, 3rd, 4th, and 5th day, respectively, N 6-11 represents the sum of the number of gilts in estrus on days 6, 7, 8, 9, 10, and 11).

[0052] The total amount of allylgestalen used in the synchronous treatment of the 25 gilts in the optimization group was T×5ml / day / gilt, that is, between 875ml-1500ml.

[0053] 3.2.2 Optimize the unit cost of synchronizing the group of 25 gilts:

[0054] Taking the market price of 450ml / bottle of allylgestalol at RMB 260 per bottle as an example, the unit cost M in the synchronous treatment of 25 gilts in the optimization group is (N1×12 days+N2×11 days+N3×10 days+N4×9 days+N5×9 days+N 6-11 ×7 days) ×5ml / day / head ÷450ml / bottle ×260 yuan / bottle ÷25 heads, which is between 20.22 yuan and 34.67 yuan.

[0055] 3.3 Effects of timed insemination technology on reproductive traits of gilts

[0056] 3.3.1 Testing of reproductive traits of gilts after primiparity

[0057] After scheduled insemination, the percentage of gilts standing still, return to estrus rate within 28 days after mating, conception rate 28 days after mating, farrowing rate, and average litter size were tracked and summarized. The test indicators are as follows:

[0058] Standing ratio = number of gilts standing ÷ number of gilts processed

[0059] Return rate = number of gilts returning to estrus within 28 days after breeding ÷ number of gilts treated

[0060] Conception rate = number of gilts with positive B-ultrasound results 28 days after mating ÷ number of gilts treated

[0061] Farrowing rate = number of farrowing gilts ÷ number of conceived gilts

[0062] Average litter size = total litter size ÷ number of farrowing gilts

[0063] 3.3.2 Testing of reproductive traits of second-parity gilts

[0064] After farrowing and weaning, the gilts are naturally estrus and bred. The gilts’ estrus rate at weaning, second-parity conception rate, and average number of piglets born in the second-parity litter are tracked and summarized. The detection indicators are as follows:

[0065] Weaning estrus rate = the number of gilts that naturally estrus within 7 days after weaning ÷ the number of gilts that farrow

[0066] Second-parity conception rate = number of second-parity B-ultrasound-positive gilts ÷ number of gilts in estrus after weaning

[0067] Average number of piglets born in the second litter = total number of piglets born in the second litter by gilts ÷ number of gilts giving birth in the second litter

[0068] 4 Experimental results

[0069] 4.1 Cost of different types of timed insemination techniques for gilts

[0070] Gilts were treated with two different timed insemination protocols: a conventional 18-day synchronization protocol (control group) and a timed insemination protocol with an optimized hormone regimen (optimized group). The study found that the total number of days of alkaloid progesterone treatment, the total amount of alkaloid progesterone used, and the unit cost of the synchronization protocol in the optimized group were significantly lower than those in the control group (P < 0.001) (Table 1). The optimized hormone regimen in the optimized group avoided excessive suppression of ovarian follicle development by alkaloid progesterone and facilitated the return of the follicle development cycle to its natural course after hormone treatment. Furthermore, the unit cost of the synchronization protocol in the optimized group decreased by 50%, significantly reducing the cost of this technology.

[0071] Table 1 Comparison of costs of different types of timed insemination techniques for gilts

[0072]

[0073] **Indicates that the difference in the same column is extremely significant (P < 0.001)

[0074] 4.2 Effects of optimizing hormone usage patterns during timed insemination in gilts on reproductive traits in primiparous pigs

[0075] Table 2 shows the effects of timed insemination with an optimized hormone pattern on reproductive traits in primiparous gilts. The results showed no significant differences in standing percentage, farrowing rate, and average litter size between the optimized and control groups. The return to estrus rate in the optimized group was significantly lower than that in the control group (P < 0.05), while the conception rate was significantly higher than that in the control group (P < 0.05). Although there were no significant differences in standing percentage, farrowing rate, and average litter size between the timed insemination with an optimized hormone pattern and conventional timed insemination, the timed insemination with an optimized hormone pattern significantly reduced the return to estrus rate and increased the conception rate in primiparous gilts.

[0076] Table 2 Effects of different types of timed insemination techniques on reproductive traits of gilts

[0077]

[0078] *Indicates significant difference in the same column (P < 0.05)

[0079] 4.3 Effects of optimizing hormone usage patterns during scheduled insemination in gilts on reproductive traits of the second litter

[0080] Gilts treated with timed insemination technology using an optimized hormone usage pattern farrowed and farrowed. The proportion of pigs in natural estrus within 7 days after weaning was significantly higher than that in the control group (P < 0.05). Although there was no significant difference in the second-parity conception rate between the optimized and control groups, the average litter size of the second litter in the optimized group was significantly higher than that in the control group (P < 0.05). The results suggest that timed insemination technology using an optimized hormone usage pattern can significantly improve the weaning estrus rate of gilts, which is beneficial for resolving the problem of inconsistent weaning estrus in gilts and promoting the development of batch breeding production. In addition, this technology can increase the average litter size of second-parity gilts, further contributing to the realization of the reproductive potential of gilts.

[0081] Table 3 Effects of different types of timed insemination techniques on reproductive traits of second-born gilts

[0082]

[0083] *Indicates significant difference in the same column (P < 0.05)

[0084] The present invention addresses the defects in the existing timed insemination technology for gilts and achieves the purpose of improving the reproductive performance of gilts with a small amount of exogenous hormones. By implementing a short period of synchronization treatment from the late luteal phase to the early follicular phase of the gilt's ovarian cycle, the current 18-day synchronization treatment time can be reduced to 7-12 days, significantly reducing the amount of progesterone hormones used, thereby avoiding the long-term stimulation of the ovaries by progesterone hormones, protecting ovarian function, and establishing a feasible technology for the continuous and stable reproduction and production of gilts. At the same time, since the optimization of the synchronization treatment time reduces the amount of progesterone hormones used, the cost of using the drug is greatly reduced, and the economic benefits of the application of the timed insemination technology in gilts are improved.

Claims

1. A method for timed insemination of gilts with optimized hormone usage pattern, characterized in that: The steps include: 1) Selecting gilts: Select gilts in estrus. The estrus span of the selected gilts should be within 11 days. 2) Synchronization treatment: Gilts that came into estrus on the 1st, 2nd, 3rd, 4th, 5th, and 6th days were fed alprogesterone starting on the 16th day after estrus, and continued to be fed for 12, 11th, 10th, 9th, 8th, and 7th days respectively; Gilts that came into estrus on the 7th, 8th, 9th, 10th, and 11th days were fed alprogesterone starting on the 15th, 14th, 13th, 12th, and 11th days after estrus, and continued to be fed for 7 days respectively; the feeding amount of alprogesterone in the synchronization treatment was 20mg / head / day; 3) Perform superovulation. The specific operation of superovulation is as follows: 42 hours after stopping feeding allylgestalone, 1000 IU PMSG / gilt is injected intramuscularly. 80 hours after the intramuscular injection of PMSG, 100 μg GnRH / gilt is injected intramuscularly. 4) Artificial insemination.

2. The method for timed insemination of gilts with optimized hormone usage pattern according to claim 1, characterized in that: Step 1) Select estrus gilts over 210 days old.

3. The method for timed insemination of gilts with optimized hormone usage pattern according to claim 1, characterized in that: Step 4) Artificial insemination: The specific operation is as follows: the first artificial insemination is performed 24 hours after the intramuscular injection of GnRH, and the second artificial insemination is performed 16 hours after the first artificial insemination.

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