Tóm tắt Luận án Selection and pure breeding of two egg-oriented D629 and D523 chicken lines

Nội dung text: Tóm tắt Luận án Selection and pure breeding of two egg-oriented D629 and D523 chicken lines

1. MINISTRY OF EDUCATION AND MINISTRY OF AGRICULTURE AND TRAINING RURAL DEVELOPMENT NATIONAL INSTITUTE OF ANIMAL SCIENCE PHAM THUY LINH SELECTION AND PURE BREEDING OF TWO EGG-ORIENTED D629 AND D523 CHICKEN LINES Major : Animal Genetics and Breeding Code number : 9 62 01 08 BRIEF INFORMATION OF PhD THESIS Ha Noi-2021
2. The work was completed at National institute of animal science Supervisors: Doctor. Nguyen Quy Khiem Assoc Prof. Doctor. Nguyen Huy Dat Reviewer 1: Prof. Doctor. Nguyen Duy Hoan Reviewer 2: Assoc Prof. Doctor. Do Vo Anh Khoa Reviewer 3: Doctor. Ngo Thi Kim Cuc The dissertation will be defended at the National thesis council at: National institute of animal sciences, Time: h date Month year of 20 The dissertation can be found at: - National library - Library of NIAS
3. INTRODUCTION 1. Problem Statement In order to achieve the strategic goals of livestock development and adaptive production system. In the past, our country has had access to high-yielding poultry genetic resources in the world, conducted selection and breeding and developed some exotic chicken breeds. At the same time, some high-productivity chicken lines, with oriented-eggs, has been selection and breeding. Imported chicken breeds, which have high egg production,have been developed such as: Leghorn white, ISA brown, Brown nick, Goldline 54, Moravia, Hisex whiter, Hyline, etc. From exotic genetic resources, some authors have selected, crossbreeding (using the method of selection based on phenotypic value) to create lines for domestic production such as research Nguyen Huy Dat (1991) white Leghorn chickens; Phung Duc Tien et al. (2012) two chicken lines HA1 and HA2, Nguyen Quy Khiem et cs. (2016) four lines of GT chickens, In 2016, The framework of the bilateral cooperation program between Vietnam and the Czech Republic to development of Czech egg-oriented chickens in Vietnam have been selected and imported two lines of egg-oriented chickens, the white feathered D629 line and brown feathered D523 series from DOMINANT CZ. These are two purebred chicken lines with high egg production, good egg quality, and the yolk ratio of egg has around 28-30%, which is 2-3% higher than other high-yielding chicken line. According to the company's documents, egg yield/hen/68weeks of age and egg weight of line D629 reached 269.81 eggs and 59.90g, and line D523 reached 258.37 eggs and 61.50g. Through studies on imported chicken breeds in our country, especially purebred lines, both egg yield and weight of these two lines have not been achieved as announced by the company. Thus, in order to effectively exploit the reproductive performance traits and develop the precious genetic resources of these two chicken lines in Vietnam, it is necessary to continue to select and purebred breed to maximize the genetic potential of the yield traits. At the same time, creating a hybrid between two lines with high egg yield and quality, eggshell color suitable to consumer’s tastes. Therefore, the study "Selection and pure breeding of two egg- oriented chicken lines D629 and D523" was selected as the thesis topic. 2. Objectives of the study - Selecting and improving the egg yield of the D629 rooster line. - Selecting and improving the egg weight of the D523 hen line. - Evaluating the production ability of commercial crossbred chickens created between D629 rooster line and D523 hen line. 3. Scientific and practical significance of the study 1
4. 3.1. Scientific meanings - Successfully selected the D629 male line with high egg yield; D523 female line had high egg weight. From two egg-oriented D629 and D523 chicken lines, commercial hybrid chicken had been created with heterosisin egg production. - The research results of the topic are a valuable scientific basis for the research on selection and breeding of livestock, as well as a valuable scientific document for teaching, learning, research at training institutions, poultry breeding establishments in general and egg-oriented chickens in particular. 3.2. Practical significance - The research results of the thesis opened the possibility of application from two egg-oriented chicken lines (D629 rooster line and D523 hen line) to produce commercial chickens with high yield egg, good egg quality and high yolk ratio, especially the eggshell with pink-white color, suitable to consumer’s tastes, contributing to providing a valuable food source for the society. - Enrich the genetic resources of our country's egg-oriented chicken breeds. 4. New contributions of the dissertation - The research results of the thesis have contributed to perfecting the method of selecting egg-oriented chicken breeds in our country based on breed value estimated by BLUP, have determined the genetic parameters analyzed by statistical model through the software PEST and VCE, have brought high efficiency in breed selection; - On the basis of the estimated breed value on egg yield trait at 38 weeks of age for D629 rooster and egg weight 38 weeks old for D523 hen, has selected a breed of D629 rooster with high egg yield, reaching 263.87 eggs/hen/68 weeks of age, increasing 11.28 eggs compared to the starting generation and a breed of D523 hen with high egg weight, reaching 64.14g; increasing 2.27g compared to the starting generation; - From 2 chicken lines D629 and D523, a commercial hybrid chicken DTP1 was created, with an outstanding hybrid advantage in egg yield of 4.22%. Eggs had good quality, yolk ratio reached 30.23%, eggshell color was pinkish white, suitable for consumer tastes. It has contributed to the enrichment of high-quality egg- oriented chicken breeds in Viet Nam. 5. Dissertation layout The thesis includes: 114 pages, 3 chapters, 40 tables, 9 pictures, references 141 domestic and international documents (44 documents in Vietnamese and 97 documents in foreign languages). There are 3 published research paper related to the Thesis. 2
5. CHAPTER 1 LITERATURE REVIEW 1.1. Scientific knowledge for some performance traits in chickens The research case of the thesis is based on the scientific knowledge of some yield traits in chickens, the selective method to estimate the breed value by BLUP, the scientific basis of economic hybridization and hybrid advantage. 1.2. Research statement in Vietnam and abroad The thesis has assessed the research statement of international and domestic following contents: study on heritability and genetic correlation in chicken selection, study on selection in chickens: The study on selection and breeding of chicken eggs in the country has also achieved encouraging results. Studies have focused on selection of morphology characteristics, egg yield, egg weight (Nguyen Huy Dat, 1991; Tran Cong Xuan et al., 1999; Phung Duc Tien et al., 2004 and 2012; Nguyen Quy Khiem et al., 2016; ). However, the method of selection by phenotypic value, mainly still uses the analysis of variance method to calculate genetic parameters. Recently, The selection base on color-oriented broiler chickens which has been applied to the modern method of selection by the BLUP method. Hoang Tuan Thanh (2017), selecting 2 chicken lines (LV4 and LV5 lines) showed that the heritability of egg yield trait traits was 0.46 and 0.15. Pham Thuy Linh and et al (2020), selection of 3 TN chicken lines (over 3 generations) showed heritability of egg yield trait 0.12- 0.19. There has not been any report on selecting broiler chickens using the systematic BLUP method of selection based on breed value, perhaps a few new studies only evaluate through genotype value modeling and using methods to calculate genetic parameters using animal models. In poultry breeding, in order to get high-yield breeds imported from abroad, only unisexual progenitor, parents and commercial products could be imported, the pure lines is difficult to import. On the other hand, according to studies on imported chicken and egg breeds in our country, it showed that egg productivity and egg weight have not been achieved as announced by the company. Since 1974, when Vietnam has supported a set of chicken breeds, specializing in white Leghorn chicken breed with X chicken line X and Y chicken line for high egg yield by Cuba. This is the second time that Vietnam has imported 2 lines of chickens D629 and D523 from Dominant company. To select and maintain high productivity of 2 chicken lines (D629 and D523), it is necessary to select 2 lines with the aim of improving egg yield, stabilizing egg weight for the male line (D629) and improving weight eggs, stabilizing egg production for female lines (D523). Selection through generations based on the 3
6. estimated breeding value by the BLUP method. Genetic parameters were estimated by the REML method on VCE 6.0.2 statistical software. Estimated breeding value was estimated by BLUP method on PEST 4.2.3 software. The statistical model using genetic analysis is a multi-trait animal model. In present, this is an advanced and highly effective method in poultry breeding. Genetic progress was obtained by regressing breed value over each generation and evaluating the selection response of 2 chicken lines. This is the research direction and implementation of this thesis. CHAPTER 2 MATERIALS, CONTENTS AND METHODS 2.1. Materials, locations and content of the research 2.1.1. Materials - Starting generation: two chicken lines (D629 and D523) were imported from the Czech Republic; - Generation 1, 2, 3, 4 of two lines of chicken D629 and chicken D523 - Commercial hybrid chicken DTP1 which is a cross between two chicken lines (♂D629 x ♀ D523). 2.1.2. Research location Pho Yen chicken research station - Dac Son commune - Pho Yen town - Thai Nguyen province, belonging to Thuy Phuong Poultry Research Center. 2.1.3. Research duration From May 2016 to April 2021. 2.2. Research content Content 1: Determination of some morphology characteristics and peformance of two chicken lines (D629 and D523) Content 2: Selection of 2 chicken lines (D629 and D523) through 4 generations Selective D629 male chicken line for improvement egg production. Selective D523 female chicken line for improvement egg weight. Content 3: Evaluation of performance production of commercial hybrid chicken DTP1 2.3. Research Methodology 2.3.1. Research Methodology 1 Determination of morphology characteristics and peformance of two derived chicken lines (D629 and D523) Two lines of chickens were imported from the Czech Republic on May 27, 2016. The diagram of the number of chickens in the derived generation is as follows: 4
7. Diagram of the number of chickens in the starting generation (chickens) D629 Line D523 Line 01 day: 117 cocks + 510 hens 01 day: 88 cocks + 534 hens 8 weeks: 117 cocks + 488 hens 8 weeks: 88 cocks + 530 hens 18 weeks: 114 cocks+ 484 hens 18 weeks:: 87 cocks + 521 hens Reproduction: 80 cocks + 480 hens Reproduction: 80 cocks + 485 38 TT: 30 cocks + 457 hens hens 38 TT: 40 cocks + 440 hens + Morphology characteristics: color of feathers, beak, legs and crest at 01 day of age and at 18 weeks of age using the method of observation with eye and taking pictures at: 01 day old and 18 weeks old by camera. + Evaluation of growth: body weight over weeks of age. At 8 and 18 weeks of age, the whole herd were weigh. Remove those that do not meet the standards such as clubfoot, crooked beak or some other deformity that moves to the laying hen stage. Feed consumption/herd/stage. - Evaluation of reproductive traits: Monitor individual laying hen for egg production from laying the first egg to 38 weeks of age. Egg weight: weigh all eggs laid at 37-38 weeks of age, using an electronic balance with an accuracy of ± 0.5g. Number of chickens taken to replace the flock of the next generation (according to the diagram above). Number of families in each line: D629 was divide in to 30 families, D523 was divide in to 40 families. 2.3.2. Research Methodology 2 Selection of 2 chicken lines (D629 and D523) through 4 generations. Selective method: - Selection for growth trait: Body weight at 8 and 18 weeks old: this criterion was selected to stabilize, taking roosters and hens whose weight was in the mean ± 2δ range. Combined with phenotype, remove individual that do not meet the standards such asclubfoot, crooked beak or some other deformities (applicable to both lines D629 and D523). - Selective reproductive traits + Rooster D629: Selection for the egg yield trait over 38-week-old was the most important: Individual monitoring of egg production from first egg laying to 38 weeks of age, selection for estimated breed value (EBV), selection of males and hens have a high to low EBV for egg production but not below the average breed value. To ensure 5
8. stable egg weight, apply average egg weight as the standard, give preference to choose males and hens whose weight was around the mean value (Mean ± 2δ), until there are enough herd, The number of chickens per generation is shown in Table 2.1. + Hens D523: Selecting the trait of egg weight at 38 weeks of age was the most important, to weigh all eggs laid at the age of 37-38 weeks, using an electronic balance with an accuracy of ± 0.5g; selection for estimated breed value (EBV), selecting roosters and hens with a high to low EBV in terms of egg weight. To ensure stable 38-week- old egg production with average egg production as the standard, priority should be given to selecting hens and hens whose egg production was around the mean value (Mean ± 2δ), until there are enough herd. The quantity and number of chickens per generation was shown in Table 2.1. The selection method as above, through 4 generations, the number of selected chicken in flocks is shown in Table 2.1. Table 2.1. Number of chickens used on the flock selected over 4 generations (heads) D629 Line D523 Line Generation Targets Male Female Male Female Number of chickens 1 day old 2824 3185 Number of chickens 8 weeks old 1371 1362 1524 1548 Number of chickens selected at 253 1162 418 1352 8 weeks old G1 Number of chickens 18 weeks old 245 1119 403 1302 Number of chickens selected for 101 978 212 1.180 spawning Number of chickens chosen to 30 436 40 571 replace the flock (38 weeks old) Number of chickens 1 day old 2296 3140 Number of chickens 8 weeks old 1100 1109 1510 1525 Number of chickens selected at 270 998 444 1384 8 weeks old G2 Number of chickens 18 weeks old 260 965 430 1332 Number of chickens selected for 147 833 233 1199 spawning Number of chickens chosen to 30 496 40 601 replace the flock (38 weeks old) Number of chickens 1 day old 2575 3140 Number of chickens 8 weeks old 1237 1253 1507 1520 G3 Number of chickens selected at 355 1109 450 1379 8 weeks old Number of chickens 18 weeks old 344 1069 433 1327 6
9. Number of chickens selected for 154 962 238 1163 spawning Number of chickens chosen to 30 574 40 616 replace the flock (38 weeks old) Number of chickens 1 day old 2568 3242 Number of chickens 8 weeks old 1236 1245 1564 1565 Number of chickens selected at 385 1121 450 1411 8 weeks old G4 Number of chickens 18 weeks old 375 1081 434 1365 Number of chickens selected for 174 927 238 1210 spawning Number of chickens chosen to 30 556 40 644 replace the flock (38 weeks old) Pure line breeding method Using a closed cloning method, rotate the male across generations to avoid inbreeding. The D629 line has 30 families, each family consists of 1 cock and 13- 20 hens. The D523 line has 40 families, each family consists of 1 cock and 12-17 hens (depending on the generation, shown in Table 2.1). Each family has 1 and 1- 2 substitute chicken. Methods of observationg and collecting data Methods of collected eggs, incubationfor selection : collected and recorded eggs to incubate instead of flocks, numbering breeding eggs: using a pencil and typing as follows: numerator is family, denominator is mother (1/2) ; individual hatching: there is a tray to block the individual so that when stacking eggs, each mother is a separate cell. Chickens are marked with individual numbers from hatching time (individual numbers: 1, 2, 3, 4, ) and recorded in the individual incubation book to track the pedigree of each generation. Set up a system of document and record data (number of chickens in the barn, number of animals lost, daily feed amount, number of eggs collected daily, body weight , egg weight, incubation book, etc.) Methods of analyzing variance components and genetic parameters Components of variance and genetic parameters of the selected trait were estimated by REML method on VCE 6.0.2 software. breed values were predicted by BLUP method on PEST software 4.2.3. Statistical model for genetic analysis of egg yield at 38 weeks of age (for D629) and egg weight at 38 weeks of age (for D523) as follows: Yijk= µ + THi + aj + eijk Where: Yijk: obtained value of observe trait; µ: mean value of the population; THi: fixed effect of generation factor (i = 1,4); aj: cumulative genetic influence of the j.th individual; eijk: random error. Method to determine the effect of fixed factors on yield traits Determining the effect of generation factor on yield traits by General Linear 7
10. Model (GLM). Statistical model: Yij = µ + THi + eij In which: Yij: obtained value of observe trait; µ: mean value of the population; THi: the influence of generational factors; eij: random error. Methods for assessing genetic predisposition and genetic progress The genetic propensity of the studied trait was evaluated based on the variation of the mean breeding values per generation. The genetic progress of each trait was determined by linear regression of the generation mean through the regression equation: y = a + bx In which: y: the same value as the studied trait; a: constant; x: generation (x = 1, 4), b: regression coefficient (increase/decrease of breed/generation value) is genetic progress. 2.3.3. Research Methodology 3 DTP1 commercial crossbred chickens were created from D629 male and D523 hens, obtained from generation 3. The experiment was arranged in a completely randomized one-factor design to evaluate commercial chicken performance. Total number of 1-day-old hens/group was 300 (repeated 3 times). Among the plots, there were similarities in age, care, nurturing, veterinary procedures for disease prevention. The only difference in experimental factors: experimental batches with different types of chickens. Research period: from July 2019 to April 2021. Nurturing care methods The chickens are cared for, and cleaned according to the egg-oriented chicken breeding process of the Thuy Phuong Poultry Research Center and the documents of Dominant CZ. Breeding method: The chicks, broilers, broodstock and DTP1 commercial hybrids in the reproductive stage were raised in a coop with a cooling system. Laying stage: for 2 lines of chicken D629, D523 from starting generation to 4th generation chickens were raised on a cage system, modern equipment, 1 chicken/cage and applying artificial insemination. Two lines of chickens D629, D523 and commercial chickens DTP1: from 01 day of age to 8 weeks of age, free feeding; period of 9-18 weeks of age with quantitative feeding; reproductive stage feed according to the rate of laying. Determine of indexes Monitoring indicators are determined by methods in poultry production (Bui Huu Doan et al., 2011). Data processing methods Statistical processing software such as EXCEL, Minitab 16.2.0. Presenting a table of results using 3 statistical parameters are sample size (n), mean value (Mean) and standard deviation (SD) (genetic parameters using standard error, SE), results take up to 3 decimal places. Using the method of analysis of variance (ANOVA) to evaluate the difference in body weight and egg productivity over generations. Compare percentage values with χ2 using MINITAB 16.2.0 software. 8
11. CHAPTER 3 RESULTS AND DISCUSSION 3.1. Determination of some appearance and yield characteristics of two derived chicken lines D629 and D523 3.1.1. Appearance characteristics of two chicken lines Line D629: At 1 day old and 18 weeks old, cocks and hens have white feathers, yellow beak and legs, bright red single crests. Line D523: At 1 day old and 18 weeks old, roosters and hens have brown feathers, yellow beak and legs, scarlet single crest. 3.1.2. Survival rate of two chicken lines The survival rate of 2 chicken lines D629 and D523 at the age of 1 day and 8 weeks for roosters was 100.00% and hens was 95.69-99.25%. In the period of 9- 18 weeks of age, the survival rate of roosters reached 97.44-98.86% and hens reached 98.30-99.39%. Thus, two chicken lines D629 and D523 had good adaptability and disease resistance in Vietnam's climate. 3.1.3. Body weight of two chicken lines Body weight at 8 weeks of age of line D629 rooster was 701.50g, hen was 574.74g; Compared with the Company, respectively, 97.43 and 96.19%. Line D523 rooster was 832.96g and hen was 631.23g; Compared with the firm, respectively, reached 101.58 and 98.63%. The body weight of an 18 weeks old D629 rooster was 1,674.88g and hen was 1,271.79g (equivalent to 104.68 and 97.83% compared to the firm). The D523 rooster line was 2,046.53g and the hen was 1,477.07g (reaching 100.32 and 100.14% respectively compared to the company). Thus, chickens D629 and D523 had the same body weight compared to the firm. Compared with the study of Pham Thuy Linh (2010), hens HA1 and HA2 at 8 weeks old reached 738.11-742.67g; At 18 weeks of age, reaching 1,409.44-1,436g, the result of the hen line D629 has a lower weight, the line D523 is higher. 3.1.4. Feed consumption of two chicken lines Feed consumption/bird: 1NT-8 weeks old: line D629 rooster: 1,773.03g and hen: 1,666.49g; line D523 1,841.14 and 1,708.42g, respectively. In the period of 9-18 weeks of age, line D629 roosters 4,929.40g and hens: 4,722.20g; line D523 respectively 5,205.48 and 4,854.78g. Phase 1 day old -18 weeks old line D629 rooster 6,702.43g and hen 6,388.69g; line D523 7,046.62 and 6,563.20g, respectively. The results of feed consumption/head of the two chicken lines were lower than that of the study of Phung Duc Tien et al. (2012) HA cocks was 8.34 - 8.68 kg and hens was 7.24-7.41 kg. 3.1.5. Laying age, hen weight and egg weight at 5% laying rate, peak and 38 weeks of age of the two parent lines The D629 line had a 5% laying age of 137 days and the D523 line was 139 9
12. days. The peak laying age of D629 chickens was 205 days; chicken line D523 was 209 days (week 30), suitable for domestic chicken breeds. Pham Thuy Linh (2010) reported that the peak laying age of HA12 chickens was 209 days, so the D629 line was 4 days earlier and the D523 line was similar. Weight of hens at 38 weeks of age: line D629: 1,762.00g; D523 line: 1,880.67g. 3.1.6. Yield of 38-week-old eggs of two primary-generation chicken lines Table 3.1. Egg yield at 38 weeks of age of two lines D629 and D523 THXP Herd Target D629 Line D523 Line Quantity 480 485 Chicken Egg/hen yield 95.58 93.06 population SD 18.23 18.81 Quantity 457 440 Population Egg/hen yield 98.39 97.67 selected SD 13.32 12.16 Egg yield/hen/38 weeks of age, the population of the D629 line reached 95.58 eggs, the D523 line reached 93.06 eggs; higher than the results of Phung Duc Tien et al. (2012) breeding through generations of egg-oriented chickens HA1 was 87.25-87.85 eggs, HA2 was 82.10-83.44 eggs. 3.1.7. Laying rate, egg yield and feed consumption/10 eggs of two chicken lines The average laying rate/68 weeks of age of chicken line D629 was 73.64%, line D523 was 71.21%. Egg yield/hen/68 weeks of age of line D629 reached 252.59 eggs, compared to the firm's 93.61% and the line D523 reached 244.24 eggs, reaching 94.53% compared with the firm. Feed consumption/10 eggs average 68 weeks old of chicken line D629 was 1.71 kg; D523 line was 1.79 kg. According to Pham Thuy Linh (2010), the egg yield/hen/68 weeks old, HA12 chickens reached 225.65 eggs; HA21 reached 219.48 eggs; HA1: 222.24 eggs; HA2: 216.42 eggs. Feed consumption/10 eggs 1.96; 2.02; 2.01 and 2.13 kg, respectively. Chickens D629, D523 have higher egg productivity and lower feed consumption/10 eggs. 3.1.8. Hatching results of the two generations of chickens Following 5 incubators from 35 to 40 weeks old, the results of the D629 line showed an average embryo rate of 93.26%, hatching/total hatching rate of 78.38%, hatching/egg with embryos was 84.04%; line D523 was 94.34; 79.35, and 84.11%, respectively. Chickens D629 and D523 apply artificial insemination, on the other hand, two newly imported purebred chicken lines hatch in hot and humid climate in Vietnam, which also affects the hatching results more or less. 3.2. Selection of two chicken lines D629 and D523 through 4 generations 3.2.1. Selective D629 rooster line improves egg production 3.2.1.1. Composition of variance and heritability of traits across generations The egg yield trait is the most important used to genetically improve the D629 chicken line. The trait of egg yield at 38 weeks of age: The cumulative genetic variance (σ²A) is 10
13. the determining factor for the magnitude of the heritability coefficient and decreases markedly from the 1st generation (96.55) to the 4th generation (35.04), accounting for 28.67% in the 1st generation, then only 12.08% in the 4th generation compared with the phenotypic variance (σ²P). The estimated heritability also tends to decrease markedly through 4 generations of selection: the 1st, 2nd, 3rd and 4th generations are 0.29; 0.18; 0.15 and 0.12, respectively. This result shows that stabilizing the D629 lineage chickens after each generation of selection reduced the genetic variability, thereby reducing genetic variance, leading to decreased heritability across generations. Table 3.2. Composition of variance and heritability of traits across generations BW 8 weeks BW 18 weeks 38 weeks old EW 38 Generation Parameters age age egg yield weeks age n 2,733 1,364 978 978 σ²A 1,158.39 6,027.55 96.55 11.92 G1 σ²E 2,631.30 12,032.70 240.30 14.30 σ²P 3,789.60 18,060.20 336.80 26.20 h2± SE 0,31±0,036 0,33±0,045 0,29±0,06 0,46± 0,04 n 2,209 1,225 833 833 σ²A 799.70 3,048.67 56.43 9.36 G2 σ²E 2,542.10 10,737.40 257.80 16.70 σ²P 3,341.80 13,786.00 314.20 26.10 h2± SE 0.24±0.02 0.22±0.03 0.18±0.04 0.36± 0.04 n 2,490 1,413 962 962 σ²A 1,026.25 3,484.19 48.38 7.36 G3 σ²E 2,092.76 9,599.01 265.41 14.35 σ²P 3,119.00 13,083.20 313.80 21.70 h2± SE 0.33±0.029 0.27±0.032 0.15±0.03 0.34± 0.04 n 2,481 1,456 927 927 σ²A 849.01 3,220.17 35.04 6.13 G4 σ²E 2,258.98 9,707.54 254.93 12.30 σ²P 3,108.00 12,927.70 290.00 18.40 h2± SE 0.27±0.026 0.25±0.035 0.12±0.03 0.33± 0.04 Note: n: number of chickens; BW: body weight, EW: egg weight, G: generation 3.2.1.2. Composition of variance of 4 generations of selection Table 3.3. Composition of variance of 4 generations of selection Parameters 38 weeks old EW 38 weeks BW 8 weeks age BW 18 weeks age egg yield age n 10518 6057 4180 4180 σ²A 991.57 4,892.35 85.43 9.93 σ²E 2,345.90 10,090.60 234.00 13.30 σ²P 3,337.40 14,982.90 319.40 23.30 11
14. The cumulative genetic variance for the 38-week-old egg yield trait was 85.43, equivalent to 26.75% of the phenotypic variance (σ²P), so for the 38-week-old egg yield trait, the external variance occupied the highest level. Therefore, in parallel with the selection to improve the genetic potential of egg yield, the external conditions such as care and management of the breeding stock, cages, food need to be ensured at the best level to promote or retain the genetic potential of this trait. 3.2.1.3. Covariance for traits of body weight, egg yield and egg weight Table 3.4. Covariance for traits of body weight, egg yield and egg weight Targets 1 2 3 4 BW 8 weeks age (1) 1,181.75 -108.15 42.77 BW 18 weeks age (2) 2,467.60 -305.16 134.52 38 weeks old egg yield (3) -179.90 -332.80 -17.47 EW 38 weeks age (4) 82.50 197.80 -2.30 Note: Values above the diagonal are genetic covariances, below the diagonal are phenotypic covariances The results showed that: there were 3 pairs of traits between body weight 8 with 18 weeks of age, body weight of 8 weeks of age with 38-week-old egg weight and 18- week-old body weight with 38-week-old egg weight genetic covariance is positive. The pairs of 38-week-old egg yield with 38-week-old egg weight, 8-week-old body weight with 38-week-old egg yield, and 18-week-old body weight with 38- week-old egg yield were all covariates genetic error negative, so genetic variation between these traits tends to be opposite. The phenotypic covariance of the above trait pairs also tends to be similar to the genetic covariance. From the relationship between the pairs of traits make more accurate decisions when considering the trait selection for efficiency. 3.2.1.4. Heritability and genetic correlations for traits of body weight, egg yield and egg weight In the D629 rooster, the heritability of the egg yield trait and the genetic correlation between egg yield and egg weight were the most important. a. Heredity coefficient The heritability of the 38-week-old egg yield trait in the D629 rooster line was 0.27. With standard error value of heritability of low egg yield trait (SE = 0.02), the estimated value had high confidence. This result was consistent with the study of Nguyen Quy Khiem et al. (2020) The genetic coefficient of Egyptian chickens in male lines was 0.23-0.27. Several studies in the world have been published, using the REML method with advanced software, the heritability of the egg yield trait was at different levels, ranging from 0.11 to 0. 54 (Nurgiartiningsih et al., 2002, 2004; Szwaczkowski, 2003; Luo et al., 2007). 12
15. Table 3.5. Heritability, genetic correlation and phenotypic correlation for traits of body weight, egg yield and egg weight Targets 1 2 3 4 BW 8 weeks age (1) 0.30±0.02 0.54±0.04 -0.37±0.06 0.43±0.04 BW 18 weeks age (2) 0.35 0.33±0.026 -0.47±0.08 0.61±0.04 38 weeks old egg yield (3) -0.17 -0.15 0.27±0.02 -0.60±0.07 EW 38 weeks age (4) 0.30 0.34 -0.03 0.43±0.03 Note: Diagonal (bold) is heritability, values above the diagonal are genetic correlations, below diagonal are phenotypic correlations. The heritability coefficient for the 38-week-old egg weight trait of the D629 rooster line was 0.43, a high value. At the same time, the heritability of body weight traits at 8 and 18 weeks of age were 0.30 and 0.33, respectively and were stable. Thus, the estimated value of the heritability of the egg yield traits of the D629 line was consistent with published domestic and foreign studies. At the same time, the standard error of heritability coefficients was low, the estimated value of heritability was reliable and the genetic stability was also quite high. Therefore, the main goal was to select for genetic improvement and keep the genetic potential of the egg yield trait promising and effective. b. Genetic correlation coefficient For broilers, the genetic correlation coefficient between egg production and egg weight was important. The results showed that the D629 line in the flock population was -0.60 and had a negative correlation, consistent with the research of some authors: (Adebambo et al., 2006; El-Labban et al, 2011; Oleforuh-Okoleh, (2011) Abdel-Ghany (2011) genetic correlation in Mandarah chickens over three generations was negative (-0.41). Le Thanh Hai et al. (2021) BT color feathered chicken line was -0.75. The genetic correlation coefficient between body weight at 8 and 18 weeks of age was positive and quite close (0.54), body weight at 8, 18 weeks of age with egg weight at 38 weeks of age was also positive: 0.43 and 0.61. The corresponding phenotypic correlation was 0.35; 0.30 and 0.34. This result was consistent with the announcement of Dang Vu Binh (2002) that genetic correlation and phenotypic correlation of body weight and egg weight were 0.42 and 0.33. The genetic correlation between body weight at 8 and 18 weeks of age and egg yield at 38 weeks of age was inversely correlated with a value ranging from -0.37 to -0.47. Identifying genetic correlation helps reference breeders to reduce the number of traits in selection to improve efficiency in breeding. 3.2.1.5. Breed value, genetic predisposition and genetic progress for 38-week- old egg yield 13