Vol. 11, Special Issue 8 (2022)

Materials and Methods: The proposed study was carried out on Cobb 400 broilers with a view to find out the seasonal impact on heat shock protein 70 and cortisol level of broiler chicken at five different agro-climatic zones prevalent in Assam viz. Upper Brahmaputra Valley (Z₁), Hill Plateau (Z₂), North Bank Plain (Z₃), Central Brahmaputra Valley (Z₄) and Lower Brahmaputra Valley (Z₅) from March 2017 to February 2018 which had different temperature, rainfall and relative humidity values. The stress response of the experimental birds was examined at 14^th, 28^th and 42^nd day of age. Fifty birds were selected randomly in each season from selected farms under study for collection of blood. The blood for serum sampling were collected by puncturing the wing vein of randomly selected experimental birds (n= 50 each season) under sterile condition in clot-activated vacutainer tubes, and transported in water proof containers containing crushed or dry ice to the laboratory. Clotted blood samples were centrifuged for 20 min at 1500 rpm and serum was isolated and stored at -20 °C for determination of HSP-70 and level of cortisol. Concentrations of HSP-70 in serum samples collected in the present study were measured using Chicken Heat Shock Protein 70 (HSP-70) ELISA kit. For the quantitative determination of cortisol in chicken sera collected in the present study, Chicken Cortisol ELISA kit was used. All the data obtained in the present experiment were statistically analysed with Two way ANOVA using SAS System, ‘Local’ X 64­_ 7 PRO software. Statements of statistical significance were based on p<0.05 except for HSP and Cortisol which were analysed with one way ANOVA.

Result: The season wise mean serum HSP-70 level (ng/ml) of broiler chicken at 14^th, 28^th and 42^nd day of age under different agro-climatic zones have been presented in Table. 1. The mean serum HSP-70 (ng/ml) of broiler chicken at 14^th day of age, during pre-monsoon, monsoon, post-monsoon and winter seasons was 1.74±0.07, 2.16±0.09, 1.75±0.05 and 4.39±0.08 respectively. The analysis of variance indicated that serum HSP-70 level (ng/ml) of broiler chicken at 14^th day differed significantly (p≤0.05) among different seasons of Assam, where the HSP-70 level of broiler chicks in winter season was significantly (p≤0.05) higher followed by monsoon, pre-monsoon and post-monsoon seasons. However, the HSP-70 level of broiler chicks in pre-monsoon and post-monsoon season did not differ significantly (p>0.05). At 28^th day of age, the mean serum HSP-70 level (ng/ml) of broiler chicken during pre-monsoon, monsoon, post-monsoon and winter seasons was 1.81±0.03, 4.16±0.07, 1.83±0.04 and 3.52±0.07 respectively.

Conclusion: In current investigation, it was observed that the HSP-70 and Cortisol level in blood was found to be higher in adult broiler (42 days) during monsoon season due to high environmental temperature and consequent thermal stress on birds.