Evaluation Of Chicken Heat-tolerance And Gene Expression Profile In Liver Under Heat Stress

Heat stress is an important stress factor that impacts production performance of chicken, andtherefore, selection for heat resistance is one of goals in the chicken breeding in the tropics and southarea of China. In this study, full-sib or half-sib Anak40pullets at with similar weight (n=55) wereraised in a room of24-28℃, RH50%in61-65days of age. At66d, the ambient temperature wasquickly increased to (35±1)℃and when was regarded as the initial of heat stress (0h). Rectaltemperature (RT) at0,6,18,30,42,54and66h were determined for each pullet. At66h, the ambienttemperature was sharply enhanced to (41±1)℃, and heat stress survival time (HSST) as well aslethal rectal temperature (LRT) was recorded for each individual. The gap between the RT as well asLRT and initial RT were recorded as~△Tn (~△T6,~△T18,~△T30,~△T42,~△T54, and~△T66) and~△TT,respectively. The results showed that the correlations between HSST and~△Tn as well as~△TT weresignificant negative (r~△T18=-0.277and r~△TT=-0.314, respectively, P<0.05; r~△T30=-0.362，r~△T42=-0.385，r~△T54=-0.559, P<0.01). Meanwhile, the HSST (256.0±208.4min) of the pullets with low~△T18waslonger (P<0.05) than that (123.7±78.3min) of the pullets with high~△T18. Therefore, the~△T18could beused as an evaluation index for heat resistance in chicken.Twelve pullets of Anak40, full-sib or half-sib, were randomly selected at60days of age. Pulletswere divided into3groups (G1, G2, and G3, respectively) and each group contains4individuals. G1was designed as the control which did not suffer heat stress, maintaining ambient temperature at(25±1)℃; G2suffered a24-h heat stress at (35±1)℃; G3suffered a24-h heat stress at (35±1)℃andfollowed by a24-h recovery at (25±1)℃. The liver tissues were collected and the RNAs were isolatedindividually. Twelve44K Agilent Chips for gene expression profile were obtained. Two hundred andthirty five genes changed by2fold or more were identified. According to the biological processclassification method of gene ontology provided, these genes were divided into16groups: DNAmetabolic process (6), DNA replication (5), transcription, DNA-dependent (3), response tomonosaccharide stimulus (2), response to glucose stimulus (2), response to carbohydrate stimulus (2),response to hexose stimulus (2), monosaccharide metabolic process (4), fatty acid metabolic process (3),RNA biosynthetic process (3), regulation of receptor biosynthetic process (2), histone modification (3),covalent chromatin modification (3), chromosome organization (5), histone H3acetylation (2),organelle fusion (2). Considering the gene repetition among groups, there were16genes were focused.By KEGG Pathway analysis, these differential expressed genes could be divided into four categories:Galactose metabolism, Gluconeogenesis, Pyruvate Glycolysis/metabolism, and Glycerolipidmetabolism, included8genes in total. In the HSP family, only HSP60mRNA differentially expressed(2.35, P<0.05). In conclusion, an evaluation index for chicken heat tolerance was obtained, and23candidate genesrelated to heat tolerance were identified and focused. The results will be helpful in the future study onthe genetics and molecular marker for heat stress in chicken.