الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
 |  | from | 126 |  |  |
| | | from | 126 | | |
Abstract
Saadeya Saad El-Dein Mekky Mohamed: A Study of Association between Genetic Markers and Productive Traits in Layer Chicken. Unpublished Ph. D. Thesis, Poultry Production Department, Faculty of Agriculture, Ain Shams University, 2017.
The aim of this study was to measure the genetic variability in two commercial layer strains Hy-line (brown) and Hy-line (W-36) using five microsatellite markers and evaluation of their productive performance under Egyptian environmental conditions. The present study was carried out using a total of 663 layer chickens to determine egg production characteristics (447 brown Hy-line layers and 216 W-36 Hy-line layers). Egg production traits were recorded throughout the first three months of production period. However, egg quality traits were conducted at 24 weeks of age. Results indicated that brown Hy-line layers had heavier body weight than white ones. Brown layers commenced to lay at an earlier age. Brown eggs were heavier than white eggs. There was insignificant effect of strain on egg number and egg production percentage. However, egg mass was highly significant for brown layers than white ones. Data of egg quality showed that the brown Hy-line eggs were highly significant for egg weight, egg shape index, shell thickness, wet and dry shell weight and shell percentage than w-36 Hy-line eggs. Concerning internal egg quality, results indicated that brown eggs were higher than white eggs for albumen weight. However, Brown layers had higher Haugh units and yolk index than the white ones, but the differences were not statistically significant. Concerning genetic diversity of brown and white Hy-line strains, results showed that there were 18 alleles found at five loci across the two strains. The mean number of alleles per locus for the studied loci was 3.6 alleles ranged from 2 for MCW0246 to 5 for MCW0241. A total of 8 common alleles were detected versus five microsatellite loci overall genotypes. Regarding specific alleles, a total of 10 out of 18 alleles (56 %) were noticed overall loci for the two genotypes studied. 5 specific alleles were observed in HY-line (Brown). Also, 5 ones were obtained in the case of HY-line (White) strains. the microsatellite MCW0241, ADL0273, MCW0246, MCW0258 and ADL0188 gives number of alleles 5, 3, 2, 4 and 4 with a size range from 295-355, 161-183, 250-280, 161-194 and 164-200bp, respectively. The value of expected heterozygosity (He) was quite high ranging from 0.5556 to 0.6444 with the average of 0.6121 while, observed heterozygosity (Ho) was 1.000 with the average of 1.000. The mean FST values of 0.1748 measured the degree of differentiations within and between strains. Where, the FST value indicated a lack of genetic differentiation between the chiken strains. The highest allele frequency overall loci was (0.50), while the lowest one was (0.100) in brown and (W-36) Hy-line strains. In addition, the highest average of allele frequency estimated was(0.50) in HY-line (W-36) strain, the lowest one was (0.33). (PIC) value for HY-line (W-36) ranged from (0.50) to (0.58) with mean 0.548 for all loci. Meanwhile, it ranged from 0.50 to 0.62 with mean of 0.556 for HY-line (Brown) strain. These differences reflect high genetic variability within HY-line (Brown) strain.
Key words: Microsatellite markers, genetic diversity, Brown Hy-line,
W-36 Hy- line strain, productive performance, egg quality.