Associations Between Hair Follicle Density, Biochemical Indicators And Polymorphism In HSP70 Gene With Chicken Survival Duration From Heat Stress

300 chickens of similar weight (F1 population of Anka Chicken♂X Lingnanhuang Chicken♀) were selected randomly in order to investigate the survival duration of chicken under a condition of prolonged high heat stress and study the associations between hair follicle density, biochemical indicators and polymorphism in HSP70 gene with Chicken survival duration from heat stress.(1) Survival duration of chickens was determined under a condition of sustained high heat stress (38±1)℃. The results indicated that the total mortality of cocks and hens in 84 hours of heat stress were respectively 78.89% and 77.54%; the cumulative mortality of cocks in the former four periods of heat stress was significantly higher than that of hens (P<0.01); in the late three periods of heat stress, no significant difference was found between the cumulative mortality of cocks and hens.(2) 70 chickens were selected randomly to determine the hair follicle density and confer its correlation with survival duration. The results turned out that the relationship between hair follicle density of cocks and heat time were negative (P<0.01, R=-0.61), and the relationship between hair follicle density of hens and heat time were negative (P<0.05, R=-0.34).(3) Before heat stress, 30 chickens were selected randomly to determine the blood biochemical indexes by collecting blood before high heat stress and 12 hours after the high heat stress beginned respectively, in order to investigate the correlation between initial blood biochemical indexes, the change rate of blood biochemical indexes in 12 hours heat stress and survival duration. The results showed that the relationship between the initial concentration of glucose and survival duration were positive (P<0.05, R=0.42); the relationship between change rate of glucose in 12 hours and survival duration were negative (P<0.01, R=-0.79).(4) Three single nucleotide polymorphisms (SNP) were searched by means of DNA sequencing in whole coding sequence of chicken HSP70 gene: mutate in 1586 site (T→C), 1541 site (C→A) and 386 site (C→G), which were all synonymy mutations without any change in amino acids.(5) Genotypes in three mutations were detected and statistical analysis by PCR-RFLP. The frequency of three genotypes AA, AB and BB in T1586C site was 0.181, 0.495 and 0.324, respectively, the frequency of allele A was 0.429 and that of allele B was 0.571; the frequency of two genotypes CD and DD in C1541A site was 0.166 and 0.834, respectively, the frequency of allele C was 0.083 and that of allele D was 0.917; the frequency of three genotypes EE, EF and FF in C386G site was 0.679, 0.300 and 0.021, respectively, the frequency of allele E was 0.829, the frequency of allele F was 0.171. Being verified byχ2, the results revealed that the three enzyme polymorphisms in coding region of chicken HSP70 gene were all in Hardy-Weinberg balance. T1586C site was of medium polymorphism, C1541A and C386G site were of low polymorphism. T1586C site showed the highest polymorphism and a highest level of genetic diversity, while C1541A site revealed the lowest polymorphism and a lowest level of genetic diversity. The heterozygosity in T1586C site was 0.490, which showed a medium level of genetic variation; while the heterozygosity in C1541A and C386G site was 0.152 and 0.284, respectively, which revealed a low level of genetic variation.(6) The relationships among three different SNPs genotypes in HSP70 gene , different diplotypes constructed by three SNPs and survival duration were analyzed. The result revealed that there was no singnificant difference in survival duration neither in different genotypes of three variable sites nor in 11 different diplotypes identified in experimental chickens.