Manipulação térmica sobre a expressão dos genes do crescimento e choque térmico durante o período embrionário e pós-natal em codornas

Abstract

Heat stress is one of the main sources of oxidative stress. Studies have shown that heat stress during the embryonic period significantly affects animal physiology and may impair body development. Heat shock proteins (HSPs) are important for the animal's organism for providing cellular protection against heat stress through different mechanisms, including developing thermotolerance, modulation of apoptotic and anti-apoptotic signaling pathways, and regulation of redox conditions cell phones. Thus, our objective was to evaluate the effects of incubation temperature on the productive performance of the progeny through the following analyses: total hatching rate, birth weight, percentage of residual yolk sac at embryonic ages of 16 and 18 days, the relative weight of organs and expression of growth hormone receptor gene (GHR), insulinlike growth factor 1 (IGF1) and heat shock protein 70 kDa (HSP70) genes. For this, 200 quail eggs (Coturnix coturnix japonica) were incubated at two different temperatures: 37.5°C (control - CTL, n = 100) and 38.5°C (high temperature - AT, n = 100) . On the 16th and 18th day of incubation, the eggs were weighed and 6 embryos of each age were randomly selected from each incubator (CTL and AT), then they were weighed and the organs were extracted for weighing and gene expression analysis(liver). After hatching, 120 healthy chicks were weighed at birth and divided into 2 treatments according to incubation temperature (CTL, n = 60 birds; and AT, n = 60 birds). At 15 days of life, 6 birds from each treatment were randomly selected, weighed and slaughtered for the collection of organs to be used in the analysis of relative weight of organs and gene expression. The present study showed that embryos incubated in AT had a higher total hatching rate (74.36 ± 20.52%) than eggs incubated in CTL (65.00 ± 18.36%) (P<0.05). Significant differences (P<0.05) were observed in relation to the relative weight of the organs between the AT and CTL treatments both at E16 and E18 embryonic ages. Embryos from eggs incubated in AT at age E16 had higher embryonic weight (PE), relative intestinal tract weight (PRTI), and relative weight of proventriculus + gizzard (PRPM), and embryos incubated at CTL temperature had higher relative yolk sac weight (PRSV) and relative heart weight (PRC) (P<0.05). At embryonic age E18, embryos from eggs incubated in CTL had higher egg weight (PO) and PRSV, and embryos from eggs incubated in AT had higher relative liver weight (PRF) and PRC (P<0.05). Chicks with 15 days of age from eggs that were incubated in the CTL, were demonstrated to have higher values of PRF, relative spleen weight (PRB), and PRTI when compared to those chicks from eggs incubated in AT (P<0.05). The results of gene expression in the liver showed that embryos aged E16 incubated at high temperature showed higher expression of genes GHR and HSP70 (P<0.05) when compared to embryos incubated at control temperature. As for embryos aged E18, as well as chicks aged 15 days, the high incubation temperature resulted in greater expression of the GHR and IGFI genes (P<0.05). Thus, we can conclude that the incubation temperature can influence important parameters in embryonic development with consequences also in the post-hatching period.