A breeding method of large-sized high-quality black pigs

Abstract

This invention belongs to the field of black pig breeding technology, specifically relating to a method for breeding large-sized, high-quality black pigs. The method involves crossing purebred Songliao black pigs with purebred Berkshire pigs to obtain F1 generation hybrid pigs. The F1 generation hybrid pigs are backcrossed twice with purebred Songliao black pigs to obtain B2 generation hybrid pigs. The B2 generation hybrid pigs are then crossbred to obtain a basic breeding herd of black pigs. This basic breeding herd is then subjected to closed breeding and successive selection for at least six generations to obtain large-sized, high-quality black pigs. The large-sized, high-quality black pigs of this invention have a Berkshire bloodline content of 12.5%, retaining the high fertility and excellent meat quality of Songliao black pigs, while effectively introducing the growth rate and intramuscular fat deposition advantages of Berkshire pigs. The large-sized, high-quality black pigs of this invention have all-black coats, reach 100kg at ≤175 days of age, have a live intramuscular fat content ≥3.5%, and a litter size ≥10.5 piglets, and can be self-breeding.

Description

Technical Field

[0001] This invention belongs to the field of black pig breeding technology, specifically relating to a method for breeding large-sized, high-quality black pigs. Background Technology

[0002] High-quality black pork, due to its high intramuscular fat content, tender texture, and rich flavor, is gradually becoming a mainstream choice for high-end meat consumption. Songliao black pigs are an excellent breed, possessing advantages such as high fertility, tolerance to roughage, strong disease resistance, and excellent meat quality. However, their growth rate is relatively slow, their backfat is thicker, and their body structure is not ideal, making it difficult to fully meet the dual requirements of modern large-scale farming for growth efficiency and carcass quality. Berkshire pigs have advantages such as fast growth rate, strong intramuscular fat deposition ability, good precocity, and compact body shape. However, purebred Berkshire pigs have lower fertility and poorer disease resistance, making them unsuitable for direct large-scale promotion.

[0003] Existing technologies have been reported on binary crossbreeding between Berkshire pigs and local pig breeds, but most of these are simple crossbreeding methods utilizing heterosis, failing to create new breeds that can be stably inherited. For example, Wu Maisheng, Liu Tianming, Peng Yinglin, et al., "Binary Crossbreeding Experiment of Shaziling Pig with Berkshire and Hampshire Pigs [J]. Journal of Animal Ecology, 2011, 32(03):22-24+108," and Sun Chengzong, Liu Zhigang, Yang Xiangdong, et al., "Experiment on Fattening and Meat Quality Determination of Two-Way Crossbreeding Combinations of Commercial Lean Pigs [J]. Shaanxi Agricultural Sciences, 1984, (05):14-17," both utilize Berkshire pigs with local pig breeds for binary crossbreeding improvement. Existing technologies mostly focus on utilizing heterosis in the F1 generation, resulting in unstable genetic structure, severe segregation of traits in offspring populations, poor breed uniformity, and an inability to form new strains. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for breeding large-sized, high-quality black pigs.

[0005] The purpose of this invention is to provide a method for breeding large-sized, high-quality black pigs, comprising the following steps: Purebred Songliao Black Pigs and purebred Berkshire Pigs were crossbred to obtain F1 generation hybrid pigs.

[0006] F1 generation hybrid pigs were backcrossed twice with purebred Songliao black pigs to obtain B2 generation hybrid pigs.

[0007] B2 generation hybrid pigs were crossbred and fixed to obtain a black pig foundation breeding stock. The Berkshire bloodline of the black pig foundation breeding stock was 12.5%.

[0008] The black pig breeding stock was subjected to closed-loop breeding and successive selective breeding for at least five generations to obtain large-sized, high-quality black pigs. The Berkshire bloodline of the large-sized, high-quality black pigs was 12.5%.

[0009] The hybrid pigs obtained through two backcrosses, fixed crossbreeding, closed breeding, and subbreeding were all ranked from high to low based on a comprehensive selection index. For boars, the top 10% with an absolute intramuscular fat content of not less than 3.5% were selected for breeding. For sows, the top 20% with a litter size of not less than 12 piglets were selected for breeding.

[0010] Preferably, the method for calculating the comprehensive selection index includes the following steps: Daily weight gain, intramuscular fat content, litter size, live backfat thickness, and feed conversion ratio were selected as core evaluation traits. The raw data for each core evaluation trait were standardized to obtain the standard deviation. The overall selection index was obtained by multiplying the standard deviation of each trait by its corresponding weighting coefficient and summing the results.

[0011] Preferably, the weighting coefficients are set according to the following principle: intramuscular fat content has the highest weight, followed by daily weight gain and number of piglets, while live backfat thickness and feed conversion ratio are given negative weights.

[0012] Preferably, the weighting coefficient for intramuscular fat content ranges from 0.28 to 0.32, the weighting coefficient for daily weight gain ranges from 0.23 to 0.27, and the weighting coefficient for litter size ranges from 0.18 to 0.22.

[0013] Preferably, the weighting coefficients for daily weight gain, intramuscular fat content, number of litters, live backfat thickness, and feed conversion ratio are 0.25, 0.30, 0.20, -0.15, and -0.10, respectively.

[0014] Preferably, the hybridization method includes the following steps: Purebred Songliao Black pig sows are mated with purebred Berkshire pig boars to obtain F1. Boars from F1 with high uniformity, excellent conformation, and black hair with white hooves or all-black hair are retained for breeding to obtain F1 generation hybrid boars.

[0015] Preferably, high uniformity refers to litter piglets without genetic diseases produced by sows with a litter size of ≥12 piglets, 7 or more effective teats, strong maternal instincts, and strong protective instincts.

[0016] Preferably, the genetic disorder is an inguinal hernia, umbilical hernia, imperforate anus, or stress syndrome.

[0017] Preferably, the "good body shape" refers to a body length ≥140cm, chest circumference ≥120cm, leg and hip circumference ≥100cm, and strong limbs, straight back and waist, and compact abdominal line.

[0018] Preferably, the method of backcrossing twice includes the following steps: The F1 generation hybrid boars were backcrossed with purebred Songliao Black sows to obtain B1. The all-black-haired and well-formed boars from B1 were then used for breeding to obtain the B1 generation hybrid boars.

[0019] A second backcross was performed between B1 generation hybrid boars and purebred Songliao Black pig sows to obtain B2. B2 boars were then used for breeding to obtain B2 generation hybrid pigs.

[0020] Preferably, the method for preserving B2 seed includes the following steps: After sorting the superior body type and all-black coat piglets in B2 according to the comprehensive selection index from high to low, two sows and one boar were selected from each litter for breeding to obtain B2 generation hybrid pigs.

[0021] Preferably, the method of transverse fixing includes the following steps: By crossbreeding B2 generation hybrid pigs to fix them, individuals with 12.5% ​​Berkshire blood were obtained, thus creating the black pig foundation breeding stock.

[0022] Boars and sows of the same generation in the B2 generation of crossbred pigs were mated, and the offspring were selected for black individuals based on body size, coat color and health status to obtain the black pig foundation breeding herd.

[0023] Preferably, the closed breeding and subgeneration selection method includes the following steps: By mating boars and sows within the basic breeding herd for at least five generations to avoid the introduction of foreign blood, large-sized, high-quality black pigs can be obtained.

[0024] The total number of boars and sows in each generation of the sows is maintained at more than 60, the ratio of boars to sows is 1:4 to 5, and the annual increase in the inbreeding coefficient does not exceed 1%.

[0025] In each generation of the lineage, boars and sows with a live backfat thickness of ≤28mm at a weight of 100kg, a live intramuscular fat content of ≥3.5%, and a feed conversion ratio of ≤3.5 will be used as the sire and dam for the next generation.

[0026] Preferably, the comprehensive selection index is selected from at least two of the following: daily weight gain, backfat thickness, intramuscular fat content, number of piglets born, and feed conversion ratio.

[0027] Preferably, the purebred Songliao Black Pig sows have a fertility of 12 or more heads, 7 or more pairs of teats, and no genetic defects.

[0028] Compared with the prior art, the present invention has the following beneficial effects: 1. The method for breeding large-sized, high-quality black pigs according to the present invention includes the following steps: Crossing purebred Songliao black pigs with purebred Berkshire pigs to obtain F1 generation hybrid pigs. Backcrossing the F1 generation hybrid pigs with purebred Songliao black pigs twice to obtain B2 generation hybrid pigs. Crossbreeding the B2 generation hybrid pigs to fix their lineage, obtaining a basic breeding herd of black pigs. The Berkshire bloodline of the basic breeding herd of black pigs is 12.5%. The basic breeding herd of black pigs undergoes closed breeding and successive generation selection for at least 5 generations to obtain large-sized, high-quality black pigs. The Berkshire bloodline of the large-sized, high-quality black pigs is 12.5%. The hybrid pigs obtained from the two backcrosses, crossbreeding fixation, closed breeding, and successive generation selection are all ranked from high to low based on a comprehensive selection index. For boars, the top 10% with an absolute intramuscular fat content of not less than 3.5% are selected for breeding. For sows, the top 20% with a litter size of not less than 12 piglets are selected for breeding. The breeding method for large-sized, high-quality black pigs of this invention precisely controls the Berkshire bloodline to 12.5% ​​through two backcrosses. This bloodline ratio preserves the meat quality and growth advantages of Berkshire while avoiding the significant decrease in fertility and reduced adaptability caused by high bloodline content. This achieves simultaneous improvement of multiple traits, including IMF ≥ 3.5%, daily weight gain ≥ 750g, and litter size ≥ 11 piglets. The large-sized, high-quality black pigs of this invention are a uniformly black herd, fully meeting the aesthetic requirements for coat color in the high-end black pig market.

[0029] The breeding method for large-sized, high-quality black pigs of this invention achieves a balance of "high quality, high yield, and high efficiency." By crossbreeding to form a genetically stable new population, after six generations, the coefficients of variation in growth, reproduction, carcass, and meat quality performance are within 10%, resulting in stable performance. This eliminates the need for annual crossbreeding, significantly reducing the cost of breeding pig production and facilitating industrial-scale promotion.

[0030] 2. The large-sized, high-quality black pigs of this invention have robust bones, providing more high-quality pork bones. The southern market, represented by Hainan, has a strong demand for pork bones; surveys show that from November to March of the following year, the purchase volume of Hainan black pig ribs surges by 40%. Large-sized black pigs have backfat thickness of 36mm~43mm, a more developed skeletal support system, higher yield of marrow bones and ribs, and a richer bone broth flavor, better satisfying the preferences of southern consumers for pork bones. Attached Figure Description

[0031] Figure 1 This is a flowchart of the breeding process of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the following detailed description, in conjunction with preferred embodiments and accompanying drawings, provides a clear and complete account of the technical solutions of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0034] The purebred Songliao Black pig sows used in this invention were purchased from Feimas Livestock Co., Ltd., Gongzhuling National Agricultural Science and Technology Park. The purebred Berkshire boars were purchased from the Jilin Academy of Agricultural Sciences.

[0035] This invention employs a weighted scoring method, taking daily weight gain, intramuscular fat content, litter size, live backfat thickness, and feed conversion ratio as core traits, and summing them by weight to obtain a comprehensive selection index. 。 The specific calculation process is as follows:

[0036] 1. Data Collection When individual pigs reached a weight of 100 kg, their daily weight gain, live backfat thickness, and intramuscular fat content were measured. The number of piglets born in the first litter of the sows was also recorded. The feed conversion ratio (FCR) for the entire litter was calculated. Raw data for daily weight gain, intramuscular fat content, number of piglets born, live backfat thickness, and FCR were obtained. Specifically, daily weight gain was recorded as X1, intramuscular fat content as X2, number of piglets born as X3, live backfat thickness as X4, and FCR as X5.

[0037] Using all individuals in the current batch as a reference group, calculate the group mean and standard deviation for daily weight gain, intramuscular fat content, litter size, live backfat thickness, and feed conversion ratio. The group mean is denoted as μ. i The standard deviation is denoted as σ. i .

[0038] The Z-score method was used to process the raw data on daily weight gain, intramuscular fat content, litter size, live backfat thickness, and feed conversion ratio. The standard value of daily weight gain, S, was calculated according to formula (1). 日增重 The standard value of intramuscular fat is S. 肌内脂肪 The standard value for the number of piglets born is S. 产仔数 The standard value of backfat thickness S is calculated according to formula (2). 背膘厚 The standard value of feed conversion ratio and S料肉比 .

[0039] Formula (1): .

[0040] Formula (2): .

[0041] In the formula, S i This is the standard value. X i It can be any one of X1, X2, X3, X4 or X5.

[0042] 2. Weighting: The weighting coefficients for each trait were determined based on the genetic parameters of Songliao Black Pigs and Berkshire Pigs, as well as the market value demand for high-end black pigs. The weighting coefficient is denoted as W. i In this invention, the weighting coefficients for daily weight gain, intramuscular fat content, litter size, live backfat thickness, and feed conversion ratio are W, respectively. 日增重 =0.25, W 肌内脂肪 =0.30、W 产仔数 =0.20、W 背膘厚 =0.15 and W 料肉比 =0.10.

[0043] 3. Calculation of the comprehensive selection index The comprehensive selection index is calculated according to formula (3).

[0044] Formula (3): I = (0.25 × S) 日增重 )+(0.30×S 肌内脂肪 )+(0.20×S 产仔数 )+(0.15×S 背膘厚 )+(0.10×S 料肉比 ).

[0045] In the formula, I is the comprehensive selection index.

[0046] Example 1 A method for breeding large-sized, high-quality black pigs includes the following steps: The breeding process of this invention is as follows: Figure 1 As shown. The specific process is as follows.

[0047] (1) Crossbreed purebred Songliao black pigs with purebred Berkshire pigs to obtain F1 generation hybrid pigs. The specific method is as follows:

[0048] Purebred Songliao Black pig sows are mated with purebred Berkshire pig boars to obtain F1. Boars from F1 with high uniformity, excellent conformation, and black hair with white hooves or all-black hair are retained for breeding to obtain F1 generation hybrid boars.

[0049] The purebred Songliao Black Pigs are defined as follows: sows with a reproductive capacity of ≥12 piglets, ≥7 pairs of teats, and no genetic defects. High uniformity refers to litter piglets from sows with a litter size of ≥12 piglets, ≥7 pairs of functional teats, strong maternal instincts, and strong protective instincts, free from genetic diseases. The genetic diseases are inguinal hernia, umbilical hernia, imperforate anus, or stress syndrome. Excellent conformation refers to a body length ≥140cm, chest circumference ≥120cm, leg and hip circumference ≥100cm, with strong limbs, a straight back and loin, and a compact abdominal line.

[0050] (2) The F1 generation hybrid pigs were backcrossed twice with purebred Songliao black pigs to obtain the B2 generation hybrid pigs. The specific method is as follows:

[0051] The F1 generation hybrid boars were backcrossed with purebred Songliao Black sows to obtain B1. All boars in B1 were ranked from highest to lowest based on their overall selection index. The top 10% of boars, with an absolute intramuscular fat content of at least 3.5%, and those with all-black hair and excellent body shape, were selected for breeding to obtain the B1 generation hybrid boars.

[0052] B1 generation hybrid boars were backcrossed with purebred Songliao Black pig sows to obtain B2. All boars in B2 were ranked from highest to lowest based on their overall selection index, and the top 10% of boars with excellent conformation and all-black coat were selected. All sows in B2 were ranked from highest to lowest based on their overall selection index, and the top 20% of sows with at least 12 piglets per litter, excellent conformation, and all-black coat were selected. This yielded the B2 generation of hybrid pigs.

[0053] (3) The B2 generation hybrid pigs were crossbred and fixed to obtain a black pig foundation breeding stock. The Berkshire bloodline of the black pig foundation breeding stock was 12.5%. The specific method is as follows:

[0054] Boars and sows of the same generation in the B2 generation were mated, and the comprehensive selection index values ​​of all offspring were ranked from highest to lowest. Boars were selected from the top 10% of those with a comprehensive selection index value and an absolute intramuscular fat content of at least 3.5% (all-black individuals), and sows were selected from the top 20% of those with a comprehensive selection index value and a litter size of at least 12 piglets (all-black individuals) (all-black individuals). This resulted in the black pig foundation breeding herd.

[0055] (4) The black pig breeding stock is subjected to closed breeding and successive selection for at least 5 generations to obtain large-sized, high-quality black pigs. The Berkshire bloodline of the large-sized, high-quality black pigs is 12.5%. The specific methods are as follows:

[0056] The boars and sows in the breeding herd were crossbred for six generations. In each generation, all individuals were ranked from highest to lowest based on their overall selection index. Boars were selected from the top 10% of those with the highest overall selection index and an absolute intramuscular fat content of at least 3.5% (all-black). Sows were selected from the top 20% of those with the highest overall selection index and a litter size of at least 12 piglets (all-black). This process avoided the introduction of foreign blood, resulting in large, high-quality black pigs. These large, high-quality black pigs can be raised as commercial pigs or kept for breeding.

[0057] The total number of boars and sows in each generation of the progeny is maintained at more than 60, the ratio of boars to sows is 1:4, and the annual increase in the inbreeding coefficient does not exceed 1%.

[0058] In each generation of the lineage, boars and sows with a live backfat thickness of ≤28mm at a weight of 100kg, a live intramuscular fat content of ≥3.5%, and a feed conversion ratio of ≤3.5 will be used as the sire and dam for the next generation.

[0059] To illustrate the beneficial effects of the present invention, the following experiments were also conducted.

[0060] 1. Reproductive performance of large-sized, high-quality black pigs Seventeen sows from the sixth generation of crossbred sows in Example 1 were selected based on comprehensive production performance indicators. All selected sows were then raised under identical feeding conditions. The farrowing performance of each sow was recorded. The farrowing results of the large-sized, high-quality black pig sows are shown in Table 1. The results show that the large-sized, high-quality black pigs bred using this invention, containing 12.5% ​​Berkshire bloodline, had an average litter size of 13.06 piglets, an average live piglet count of 11.88 piglets, and a survival rate as high as 95.3%. The piglets exhibited good uniformity, with an average birth weight of 1.42 kg, meeting the breeding goals for large-sized, high-quality black pigs. This group also possesses good maternal instincts, farrowing capacity, and piglet vitality, which can meet the needs of large-scale production.

[0061] Table 1. Statistics on the farrowing rate of large-sized, high-quality black sows. 2. Growth performance and feed conversion efficiency of large-sized, high-quality black pigs Twenty commercial pigs from the 6th generation after crossbreeding fixation in Example 1 were randomly selected. All experimental pigs were fed under the same conditions, with free access to feed, and daily feed intake and weight changes were recorded. Growth performance was measured during the fattening period from 30kg to 100kg. The growth performance results of the large-bodied high-quality black pigs are shown in Table 2. The results show that the average daily weight gain of the large-bodied high-quality black pigs was 690g / day, significantly higher than the industry average, achieving the rapid growth target for large-bodied high-quality black pigs. The average feed conversion ratio of the large-bodied high-quality black pigs was 2.91, lower than 3.0, indicating high feed conversion efficiency and excellent muscle deposition efficiency, which is beneficial for reducing breeding costs. The survival rate during the fattening period was 100%, and the overall health of the herd was good, providing high-quality raw material pigs for slaughtering and processing.

[0062] The above results indicate that the large-sized, high-quality black pigs bred according to the method of this invention exhibit high growth rate and high feed conversion efficiency during the fattening period, high uniformity of the herd, and excellent health, which can significantly improve the economic benefits of breeding and meet the requirements of large-scale and high-efficiency production.

[0063] Table 2. Statistics on the growth performance of large-sized, high-quality black pigs. 3. Carcass performance and meat quality characteristics of large-sized, high-quality black pigs Ten commercial pigs from the sixth generation after crossbreeding fixation in Example 1 were randomly selected for slaughter performance testing and meat quality analysis. All experimental pigs were kept under identical feeding conditions, fasted for 24 hours before slaughter, and subjected to the same slaughtering process. The carcass performance and meat quality characteristics of the large-sized, high-quality black pigs are shown in Table 3. The results showed that the core indicators such as pre-slaughter body weight, dressing percentage, lean meat percentage, and eye muscle area all reached excellent levels, with a lean meat percentage of 60.79% and a dressing percentage of 71.85%.

[0064] Meat freshness: pH 1 is 6.23, pH 24 is 5.88, no white muscle or black dried meat, meat freshness is good.

[0065] With an intramuscular fat content of 3.52% and a shear force of 41.02 N, the meat is tender and flavorful, making it suitable for fresh consumption and chilled meat processing.

[0066] With a water retention rate of 76.28% and a cooked meat yield of 64.73%, it has low moisture loss during processing, high yield, and is suitable for various processing scenarios such as braising and marinating.

[0067] The coefficients of variation for indicators such as eye muscle area and drip loss are relatively high. It is recommended to further optimize the post-slaughter cooling process and the uniformity of feed intake during the fattening period.

[0068] The large-sized, high-quality black pigs bred by the method of this invention exhibit excellent carcass performance and meat quality characteristics, and possess good slaughter efficiency, tender flavor, and processing stability. They fully meet the breeding objectives of large-sized, high-quality black pigs and have significant market competitiveness and industrialization value.

[0069] Table 3. Statistical Table of Carcass Performance and Meat Quality Characteristics of Large-Body High-Quality Black Pigs It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the inventive concept of this invention, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0070] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If such modifications and variations fall within the scope of equivalents of this invention, then this invention is also intended to include such modifications and variations.

Claims

1. A method for breeding large-sized, high-quality black pigs, characterized in that, Includes the following steps: Purebred Songliao black pigs and purebred Berkshire pigs were crossed to obtain F1 generation hybrid pigs; F1 generation hybrid pigs were backcrossed twice with purebred Songliao black pigs to obtain B2 generation hybrid pigs; B2 generation hybrid pigs were crossbred and fixed to obtain a black pig base breeding stock; The black pig breeding stock is kept in a closed breeding and selective breeding process for at least 5 generations to obtain large-sized, high-quality black pigs. The hybrid pigs obtained from backcrossing twice, crossbreeding in a fixed and closed manner, and subsequent generations of breeding were all ranked from high to low by a comprehensive selection index. The top 10% of boars with an absolute intramuscular fat content of not less than 3.5% were selected for breeding; the top 20% of sows with a litter size of not less than 12 piglets were selected for breeding.

2. The method for breeding large-sized, high-quality black pigs according to claim 1, characterized in that, The method for calculating the comprehensive selection index includes the following steps: Daily weight gain, intramuscular fat content, litter size, live backfat thickness, and feed conversion ratio were selected as core evaluation traits. The raw data of each core evaluation trait were standardized to obtain the standard deviation. The standard deviation of each trait was multiplied by its corresponding weight coefficient and then summed to obtain the comprehensive selection index.

3. The method for breeding large-sized, high-quality black pigs according to claim 1, characterized in that, From the F1 generation of hybrid pigs obtained by crossing purebred Songliao black pigs and purebred Berkshire pigs, boars with high uniformity, excellent body shape, and black hair with white hooves or all-black hair are selected for breeding to obtain F1 generation hybrid boars.

4. The method for breeding large-sized, high-quality black pigs according to claim 3, characterized in that, High uniformity refers to litter piglets without genetic diseases produced by sows with a litter size of ≥12 piglets, 7 or more effective teats, strong maternal instincts, and strong protective instincts.

5. The method for breeding large-sized, high-quality black pigs according to claim 4, characterized in that, The genetic disorders mentioned are inguinal hernia, umbilical hernia, imperforate anus, or stress syndrome.

6. The method for breeding large-sized, high-quality black pigs according to claim 3, characterized in that, The term "good physique" refers to a body length ≥140cm, chest circumference ≥120cm, leg and hip circumference ≥100cm, and strong limbs, straight back and waist, and compact abdominal line.

7. The method for breeding large-sized, high-quality black pigs according to claim 1, characterized in that, The method of backcrossing twice includes the following steps: The F1 generation hybrid boars were backcrossed with purebred Songliao black sows to obtain B1; the all-black-haired and well-formed boars from B1 were kept for breeding to obtain B1 generation hybrid boars. B1 generation hybrid boars were backcrossed with purebred Songliao black pig sows a second time to obtain B2; By retaining B2 for breeding, B2 generation hybrid pigs were obtained.

8. The method for breeding large-sized, high-quality black pigs according to claim 7, characterized in that, The method for preserving B2 seed includes the following steps: After sorting the superior body type and all-black coat piglets in B2 according to the comprehensive selection index from high to low, two sows and one boar were selected from each litter for breeding to obtain B2 generation hybrid pigs.

9. The method for breeding large-sized, high-quality black pigs according to claim 1, characterized in that, The method for horizontal fixation includes the following steps: Boars and sows of the same generation in the B2 generation of crossbred pigs were mated, and the offspring were selected for black individuals based on body size, coat color and health status to obtain the black pig foundation breeding herd.

10. The method for breeding large-sized, high-quality black pigs according to claim 1, characterized in that, The closed breeding and subgeneration selection method includes the following steps: The boars and sows in the basic breeding pig herd are mated for at least 5 generations to obtain large-sized, high-quality black pigs. The total number of boars and sows in each generation of the procreation is maintained at more than 60, the ratio of boars to sows is 1:4-5, and the annual increase in the inbreeding coefficient does not exceed 1%. In each generation of the lineage, boars and sows with a live backfat thickness of ≤28mm at a weight of 100kg, a live intramuscular fat content of ≥3.5%, and a feed conversion ratio of ≤3.5 will be used as the sire and dam for the next generation.

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