Report on the Breeding of Dahen 799 Broilers

ChaowuYANG　ChunlinYU　MohanQIU　ZengrongZHANG　ChenmingHU　HuaruiDU　QingyunLI　XiaXIONG　ShiliangZHU　SiyangLIU　XiaosongJIANG

Abstract[Objectives] This study was conducted to improve the production efficiency of dark-shank partridge-like plumage high-quality broilers and ensure animal welfare， so as to meet the development needs of China's yellow-feather broiler industry. [Methods]Sichuan Animal Science Academy and Sichuan Dahen Poultry Breeding Co.， Ltd. formed a joint breeding research team. The team bred Dahen 799 broiler complete set line with local chicken breeds as the main material and improving production efficiency， stabilizing meat quality and flavor and achieving autosexing of chicks as the main breeding goals by modern poultry breeding technologies， after 10 years and 8 generations. [Results] The Dahen 799 broiler complete set line was approved by National Commission of Livestock and Poultry Genetic Resources in December 2020. The 66-week-old egg production of the breed reached 189 eggs. For the commercial generation， cocks and hens showed 10-week-old weights of 2 668 and 2 269 g， respectively; the feed conversion ratio was 2.26-2.35; the survivability was 96.7%-97.2%; and the average intramuscular fat contents of cocks and hens were in the range of 1.8%-2.1%， and the inosinic acid contents were in the range of 2.3-3.2 mg/g. The production performance and meat flavor of Dahen 799 broilers were better than Dahen 699 broilers， Sichuan mountainous bone-black chickens and two other social breeds. Compared with Sichuan mountainous bone-black chickens， the egg production at the age of 66 weeks increased by 47 eggs; the average weight of cocks and hens of the commercial generation at 10 weeks increased by 45.21%; and the autosexing rate of chicks of the commercial generation reached 99.3%. [Conclusions]Dahen 799 broilers have the advantages of good production performance， high feed conversion ratio and excellent meat flavor and the characteristic of autosexing which other breeds do not have， and can fully meet the industrial development needs of dark shanks and partridge-like plumage broilers.

Key wordsDahen broiler; High-quality broiler; Genetic breeding; Performance measurement

Dark-shank partridge-like plumage high-quality broilers are the main variety in the yellow-feather broiler industry in Southwest China. They are cultivated from local chicken breeds and characterized by indigotic feet， partridge-like plumage in hens and red feathers in cocks. Due to their excellent meat flavor， they are very popular among consumers[1]. However， due to the low production efficiency of indigotic-foot partridge-like plumage high-quality broiler breeds and the inability to separate males and females for chicks， there are problems such as low production efficiency， great stress during sex identification by turning the anus for chicks and the inability to ensure animal welfare， which restricts the high-quality development of the industry. To this end， Sichuan Animal Science Academy and Sichuan Dahen Poultry Breeding Co.， Ltd. formed a joint breeding team to carry out commercial breeding for bottleneck problems to meet the needs of industrial development. The breeding research team has bred Dahen S01 line， Dahen S02 line， Dahen S03 line， Dahen D99 line and Dahen S05 series and other 5 specialized indigotic-foot partridge-like plumage high-quality broiler lines by introducing breeding materials such as Sichuan mountainous bone-black chickens， Jiuyuan black chickens， Caoke chickens and adopting modern poultry breeding technologies. They also bred Dahen S08 line， Dahen S06M line， Dahen S07 line， Dahen S011 line and Dahen B01 line with the main breeding goals of improving production efficiency， stabilizing meat flavor and realizing autosexing[2-3]. Through the determination of combining ability， the selected optimal combination was named Dahen 799 broiler complete set line. This complete set line was selected and bred after 10 years and 8 generations. In December 2020， it was approved by National Commission of Livestock and Poultry Genetic Resources. In this study， we briefly introduced the breeding process， breeding technology and results of Dahen 799 broiler line， which provides technical reference for the breeding of other yellow-feather broiler lines.

Materials and Methods

Breeding material

In 2000， the breeding team introduced Sichuan mountainous bone-black chickens， Jiuyuan black chickens， Caoke chickens and other breeding materials. According to the diversified needs of the market at that time， 5 new high-quality broiler lines （indigotic foot， partridge-like plumage， white skin） were cultivated， i.e.， Dahen S01 （fast feathering）， Dahen S02 （slow feathering）， Dahen S03 （fast feathering）， Dahen S05 （fast feathering）， Dahen D99 （fast feathering）. In 2005， the 5 new lines passed the examination and approval of Sichuan Provincial Bureau of Animal Husbandry and Foodstuff and obtained the certificate of new breed （certificate number： （2005） new breed certificate No.02）. In 2010， the breeding team used the 5 pure lines as breeding materials to carry out the breeding of Dahen 799 broiler line. At that time， all 5 lines had entered the breeding of generation G9.

Breeding of new specialized lines

During the breeding of Dahen 799 broiler line， five new specialized lines were selected， namely S08 line， S06M line， S07 line， S011 line and B01 line.

Breeding of new male linesDuring the breeding of S08 line， starting from cocks of the G8 generation of Dahen S01 line and hens of the G8 generation of Dahen S03 line， a basic group was established after crossing， backcrossing and crossbreed fixation by retaining fast-feathering indigotic-foot partridge-like plumage broilers， and selection was performed with growth performance as the main breeding goal. For Dahen S01 line and Dahen S03 line， the main traits utilized were growth rate and physical appearance.

In the breeding of S06M line， cocks of the G8 generation of Dahen S02 line and hens of the G8 generation of Dahen S05 line were the initial materials， and a basic group was established after crossing， backcrossing and crossbreed fixation by retaining slowly-feathering indigotic-foot partridge-like plumage broilers， for the selection with growth performance and reproductive performance as the main breeding goals. For Dahen S02 line， the main traits utilized were physical appearance and growth rate， and from Dahen S05 line， the main traits utilized were reproductive performance and physical appearance.

Breeding of new female lines S07 line was selected from a basic group established by retaining fast-feathering indigotic-foot partridge-like plumage broilers in the G8 generation group of Dahen D99 line with reproductive performance as the main breeding goal. S011 line was selected from a basic group established by retaining fast-feathering indigotic-foot partridge-like plumage broilers in the G8 generation group of Dahen S05 line with reproductive performance as the main breeding goal. B01 line was bred from cocks in the G8 generation of Dahen D99 line and hens in the G8 generation of Dahen S05 line， which were used to perform crossing， backcrossing and crossbreed fixation， after which a basic group was established by retaining fast-feathering indigotic-foot partridge-like plumage broilers， for the selection with reproductive performance and growth performance as the main breeding goals. From the two breeding materials， the main traits mainly utilized were reproductive performance， physical appearance and growth rate.

Breeding and selection methods The main target traits of the male parent line were growth rate， population uniformity and appearance traits. The selected traits were feathering speed， feather color， crus color， crest shape and height， body shape， body weight and uniformity （1 d， 6 w， 10 w， age of caging， age at first egg， 43 w）， semen quality of cocks （age of caging， age at first egg）， and egg weight （weight of first egg， egg weight at 43 w）. The main selected traits were body weight at 10 w， weight at first egg， semen quality of cocks， body weight at 43 w， and feathering speed. Each generation was established with 80 families， each having a ratio of males to females at 1∶10， and 8 generations were selected continuously.

The main target trait of the female parent line was reproductive performance， taking into account the growth rate and appearance traits. The selected traits were feathering speed， feather color， crus color， crest shape and height， body shape， body weight and uniformity （1 d， 6 w， 10 w， age of caging， age at first egg， 43 w）， semen quality of cocks （age of caging， age at first egg）， egg weight （weight of first egg， egg weight at 43 w）， the number of eggs laid （43 w， 66 w）， and the number of healthy chicks （43 w， 66 w）. The main selected traits were body weight at 10 w， weight at first egg， semen quality of cocks， the number of eggs laid at 43 w， number of healthy chicks at 43 w and feathering speed. Each generation was established with 80 families， each having a ratio of males to females at 1∶10， and 8 generations were selected continuously.

Each line was bred by a combination of family selection and individual selection. The rate of reserved cocks in each generation was controlled at 2.0%-2.5%， and the rate of reserved hens was controlled at 20%-25%. In the breeding process， the purification and monitoring of Salmonella pullorum and avian leukosis were strictly carried out in accordance with relevant requirements.

Determination of combining force

According to the breeding goal of Dahen 799 broiler complete set line， the parental breeding chickens need to have high reproductive performance， and commercial broilers can be identified for genders by feathering speed， and have fast growth rate， high survival rate and strong disease resistance to maximize production benefits. Therefore， based on the characteristics of various lines of Dahen Company and the breeding goals to be achieved， 3 combinations were determined for the reproduction models of parental hens， and 6 combinations were determined for the production models of commercial broilers， so as to select the best complete set model. Since the commercial chicks to be bred can be autosexed by feathering speed， according to the sex-linked inheritance law of feathering speed， S06M （slowly-feathering pure line） was fixed as the first male parent in the process of combination design. The specific models of various combinations were： S08♂×（S06M♂×S07♀） （combination 1）， S08♂×（S06M♂×S011♀） （combination 2）， S08♂×（S06M♂×B01♀） （combination 3） ， S01♂×（S06M♂×S07♀） （combination 4）， S01♂×（S06M♂×S011♀） （combination 5）， S01♂×（S06M♂×B01♀） （combination 6）. The performance of the parental and commercial generations of the 6 combinations was determined and analyzed to determine the optimal hybrid combination.

Statistical analysis of data

The high-quality broiler breeding information intelligent management and analysis system[4] independently developed by the breeding team was used to collect， manage and analyze relevant performance.

Results and Analysis

Breeding of pure lines for Dahen 799 broilers

Breeding of S06M lineFrom the data in Table 1， it was calculated that the weights of cocks and hens at the age of 10 w in the 8th generation of S06M line increased by 176 and 159 g compared with the 0 generation， respectively， and the coefficients of variation decreased by 1.54 percentage points and 1.00 percentage point， respectively. The number of eggs laid at the age of 43 w increased by 9.4 eggs per hen， the coefficient of variation decreased by 9.26 percentage points， and other performance and uniformity were significantly improved. It indicated that the body weight， uniformity and laying performance of the line were greatly improved.

It can be seen from Table 2 that through the breeding of 8 generations， the homozygous proportion of the slowly-feathering genotype reached 100%， and the descendant phenotype testing showed that the slowly-feathering proportion increased from 75.6% in the 1st generation to 99.8% in the 8th generation， and the S06M line was slow. The breeding for the slowly-feathering trait progressed significantly. The results showed that in the breeding process， adopting the combination of conventional breeding and molecular breeding improved the efficiency of hybrid breeding.

Breeding of S07 lineFrom the data in Table 3， it was calculated that the number of eggs laid at the age of 43 w in the 8th generation of S07 line had an increase of 9.6 eggs compared with the 0 generation， and the coefficient of variation decreased by 4.76 percentage points. The average fertilization rate and average hatching rate of fertilized eggs increased by 1.6 percentage points and 2.7 percentage points， respectively. Other performance and uniformity were significantly improved. It indicated that the growth rate and reproductive performance of the line were greatly improved.

Breeding of S08 linesFrom the data in Table 4， it was calculated that the weights of cocks and hens at the age of 10 w in the 8th generation of S08 line increased by 153 and 152 g compared with the 0 generation， respectively， and the coefficients of variation decreased by 1.49 percentage points and 0.86 percentage point， respectively. The body weights of 66-week-old cocks and hens increased by 219 and 347 g， respectively， and the body weights at the ages of 6 and 43 w and the number of eggs laid at the age of 43 w increased significantly. It showed that the line had made remarkable progress in growth rate and reproductive performance through systematic breeding.

Complete set model for Dahen 799 broilers

Reproductive performance of hens in different combinationsIt can be seen from Table 5 that the progeny of S06M♂×S07♀ combination had higher egg production per hen housed， hen-day egg production， average fertility and hatchability of fertilized eggs at the age of 66 w than other combinations， showing excellent reproductive performance.

Performance of the commercial generation of different combinationsIt can be seen from Table 6 that the production performance of the 70-day-old commercial broilers of combination 1[S08♂×（S06M♂×S07♀）]was higher than that of other combinations. It can be seen from Table 7 that the overall differences in meat quality indices between various combinations were not significant. Combined with the measurement of the reproductive performance of the parents， combination 1 was determined as the complete set model of Dahen 799 broilers.

Production performance of Dahen 799 broilers and its comparison with other breeds

It can be seen from Table 8 that the production performance and meat flavor of Dahen 799 broiler complete set line were significantly better than those of Dahen 699 broiler line， Sichuan mountainous bone-black chickens and two other social breeds. Compared with Sichuan mountainous bone-black chickens as a breeding material， the number of eggs laid at the age of 66 w increased by 47 eggs. The average body weight of 10-week-old cocks and hens of the commercial generation increased by 45.21%， and the autosexing rate of the chicks of the commercial generation reached 99.3%. Therefore， Dahen 799 broiler line has the advantages of good production performance， high feed conversion rate and excellent meat flavor， and the characteristic of autosexing that other breeds do not have.

Discussion

Breeding effect of Dahen 799 broilers

Dahen 799 broiler line is mainly based on the genetic resources of local chicken breeds， and was bred by combining conventional breeding and molecular breeding[5]， which improves the efficiency of cross-breeding. It has the characteristics of high reproductive performance of the parental breeding chickens and fast growth rate and excellent meat quality and flavor of the commercial generation， which are in line with the national yellow-feather broiler market demand in Sichuan， Chongqing， Yunnan， Guizhou， Anhui， Shandong， Henan， etc. Dahen 799 broiler line is not only suitable for standardized scale breeding， but also suitable for ecological breeding in forests outside houses and adaptive to diversified breeding methods. In general， after 8 generations of breeding， the coefficients of variation of the 3 lines in Dahen 799 broiler complete set line were controlled within 10%， which meets the requirements for breed approval and the breeding effect is good.

Market promotion prospect of Dahen 799 broilers

In this study， the commercial generation of Dahen 799 broilers was compared with Dahen 699 broiler complete set line[6]， Sichuan mountainous bone-black chickens， social breed 1， and social breed 2. Among them， Dahen 699 broiler complete set line and Dahen 799 broiler complete set line are both fast indigotic-foot partridge-like plumage high-quality broiler complete set lines developed by our team， and Dahen 699 broiler complete set line has been extended to the main producing areas of high-quality broilers across the country and has been fully recognized by the market since its approval by the state in 2010. Sichuan mountainous bone-black chickens are the main local chicken breed in Sichuan， which has fast growth rate and excellent meat quality and flavor. Social breed 1 and social breed 2 are the complete set lines of indigotic-foot partridge-like plumage broilers that have been approved by the state in recent years. The results showed that Dahen 799 broiler complete set line is good in various production performance and has obvious market competitive advantages. It can adapt to the new situation of meat production under the condition of tight food supply， and has broad market promotion prospects.

Future work and improvements

According to relevant national policies and market demand，

the future selection and breeding of Dahen high-quality broilers will be mainly carried out from various aspects. First， we should continue to carry out research on supporting feeding and management technology and nutritional needs， formulate more reasonable and accurate nutritional standards according to the growth and metabolic needs of chickens， and optimize technical regulations for feeding and management， so as to give full play to the genetic potential of breeds. The second is to continuously carry out the monitoring and purification of pullorum and avian leukosis， optimize the immunization program， and improve the level of maternal antibodies and the quality of breeding chickens as a whole. Third， information technologies can be used to develop intelligent breeding equipment， so as to reduce human error， improve selection efficiency and speed up the breeding process. The fourth is to use new technologies and new methods to select pure lines， such as the whole genome selection technology， which can speed up the breeding progress of pure line chickens for low-heritability traits such as feed conversion efficiency and egg production performance. Meanwhile， candidate pure lines should be further selected to meet the market's future requirements for the standardization of "chilled chicken" carcasses[7]. At present， our breeding team is cultivating a complete set line of Dahen 899 broilers suitable for slaughtering and processing.

Conclusions

In this study， the breeding process and technology of Dahen 799 broilers were briefly described， and the main breeding data of the breeding process such as pure line selection and combining ability determination were statistically analyzed. The results showed that Dahen 799 broiler complete set line produced 189 eggs at the age of 66 w; the weights of cocks and hens of the commercial generation at the age of 10 w were 2 668 and 2 269 g， respectively; the feed conversion ratio was 2.26-2.35; the survivability was 96.7%-97.2%; and the average intramuscular fat contents in the meat of cocks and hens were in the range of 1.8%-2.1%， and the contents of inosinic acid were in the range of 2.3-3.2 mg/g. The complete line has the advantages of good production performance， high feed conversion rate and excellent meat quality and flavor， and the characteristic of autosexing that other varieties do not have. It fully meets the requirements of the breeding goals， and can satisfy the needs of industrial development for high-quality provenance.

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Editor： Yingzhi GUANG Proofreader： Xinxiu ZHU