The genetic of welfare: gene expression and heat stress in chicken.

High environmental temperature is one of the most important
stressors associated with economic losses to the poultry industry.
It causes poor growth performance, immunosuppression, and
high mortality, contributing thus to a production decrease.
Broilers are in general more sensitive to high environmental
temperatures than other domestic animals but the responses to
heat differ between different chicken genetic backgrounds. We
used One Step Taqman real time RT-PCR technology to evaluate
the effect of heat stress on the expression of six genes codifying
for the antioxidative enzymes (SOD and CAT), heat shock protein
(HSP) 70 and HSP90, glucocorticoid receptor (NR3C1), and
Caspase 6 (CASP6) in the liver of two chicken strains: Red JA
Cou Nu Hubbard (CN) and Ross 508 Aviagen (RO). A total of 120
RO and 120 CN broilers, 4 weeks of age, were divided into 4
groups of 60 animals, which were then reared for 4 weeks at two
different environmental temperatures: 34°C and 22°C.
Corticosterone (CORT) concentration was measured in blood
samples using enzyme immunoassay method. We also analysed
the association between transcriptomic response and specific
SNPs in each genetic strain of chickens. The results demonstrated
that there was both a genotype and a temperature effect on
the chickens’ growth, given that a different trend was seen in the
four combinations genetic strain-environmental temperature
from the 6th week to the end of the experiment. Chronic heat
stress caused a significant increase in CORT levels due to activation
of the hypothalamic-pituitary-adrenal axis in both genetic
strains. Carcass yield at slaughter were similar in all groups,
ranging from 86.5 to 88.6%, whereas carcass weight was negatively
influenced by heat stress in both breeds. Heat stress affected
the expression of quite all target genes and the differences
found in the mRNA copies of two (CASP6 and HSP70) out of the
six genes could be partly explained by SNPs. In particular, we
found three SNPs for the HSP70 gene (HSP70-3, -7, -9) with different
allelic frequencies between the two target breeds, and a
SNP polymorphism in the CASP6 gene (CASP6-9). The evidence
given in this study, on gene expression and genome polymorphisms
will be useful in the future marker assisted selection of
chickens more tolerant to heat stress.High environmental temperature is one of the most important
stressors associated with economic losses to the poultry industry.
It causes poor growth performance, immunosuppression, and
high mortality, contributing thus to a production decrease.
Broilers are in general more sensitive to high environmental
temperatures than other domestic animals but the responses to
heat differ between different chicken genetic backgrounds. We
used One Step Taqman real time RT-PCR technology to evaluate
the effect of heat stress on the expression of six genes codifying
for the antioxidative enzymes (SOD and CAT), heat shock protein
(HSP) 70 and HSP90, glucocorticoid receptor (NR3C1), and
Caspase 6 (CASP6) in the liver of two chicken strains: Red JA
Cou Nu Hubbard (CN) and Ross 508 Aviagen (RO). A total of 120
RO and 120 CN broilers, 4 weeks of age, were divided into 4
groups of 60 animals, which were then reared for 4 weeks at two
different environmental temperatures: 34°C and 22°C.
Corticosterone (CORT) concentration was measured in blood
samples using enzyme immunoassay method. We also analyzed
the association between transcriptomic response and specific
SNPs in each genetic strain of chickens. The results demonstrated
that there was both a genotype and a temperature effect on
the chickens’ growth, given that a different trend was seen in the
four combinations genetic strain-environmental temperature
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