title: Effect of cyclical cold stress during embryonic development on aspects of physiological responses and HSP70 gene expression of chicks.
abstract: The objective of the present study was to evaluate the effects of cyclical lower incubation temperature at different embryonic ages on the hatchability, body and organs weights, thyroid hormones, and liver HSP70 gene expression of newly hatched chicks. In a completely randomized design, fertile eggs of a broiler breeder (34 weeks of age) were assigned to three treatment groups with six replicates and 145 eggs per each. The treatment groups were as: control group (C) that eggs were incubated at 37.6°C during the whole incubation period; incubation temperature was decreased to 36°C for 3h per day at embryonic age from 12 to 14 (T1); and incubation temperature was decreased to 36°C for 3h per day at embryonic age from 15 to 17 (T2). No significant difference was found among treatments for hatchability (P>0.05). There were no differences (P>0.05) among treatments for body weight and liver weight, while heart weight of chicks in T1 and T2 groups were significantly higher than the control group (P<0.05). There were no differences (P>0.05) among treatments for the levels of thyroid hormones, however, the levels of both hormones tended to increase in chicks exposed to cold stress (T1 and T2). Chicks in T2 group had higher liver HSP70 gene expression compared with those in T1 and the control group (P<0.05). Cold stress in both incubation periods had no significant effect on the plasma levels of aspartate aminotransferase and alanine aminotransferase. Treatments had no effect on the plasma levels of glucose, cholesterol and triglyceride. The results of this study suggest that cyclical lower incubation temperatures (36°C) at the embryonic age from day 15-17 could induce the liver HSP70 gene expression, without negative effects on the hatchability and body weight of hatched chicks.
authors.affiliation: Department of Animal Science, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Keyvan
authors.initials: K
authors.lastname: Aminoroaya
authors.affiliation: Department of Animal Science, Science and Research Branch, Islamic Azad University, Tehran, Iran. Electronic address: a.sadeghi@srbiau.ac.ir.
authors.forename: Ali Asghar
authors.initials: AA
authors.lastname: Sadeghi
authors.affiliation: Department of Animal Science, Sari Agricultural Sciences and Natural Resources University, Sari, Iran.
authors.forename: Zarbakht
authors.initials: Z
authors.lastname: Ansari-Pirsaraei
authors.affiliation: Department of Animal Science, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Nasser
authors.initials: N
authors.lastname: Kashan
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation; D001835:Body Weight; D002642:Chick Embryo / Q000196:embryology*; D002645:Chickens / Q000097:blood / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D003080:Cold Temperature; D058639:Cold-Shock Response; D018507:Gene Expression Regulation, Developmental; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D006321:Heart / Q000254:growth & development / Q000502:physiology; D008099:Liver / Q000254:growth & development / Q000502:physiology; D008297:Male; D009929:Organ Size; D013963:Thyroid Hormones / Q000032:analysis
chemical_list: D018840:HSP70 Heat-Shock Proteins; D013963:Thyroid Hormones
keywords: Broiler chicks; Cold stress; Embryo; Heat shock protein; Incubation