Expressions of Heat-Tolerance Temperatures, Genes and Dietary Feed Additives Related to Productive Traits in Three Strains of Chickens

The main objectives of the present study are to investigate the impact of heat- stress temperature (HST) and dietary feed additives (DFA) on rectal temperature (RT), live body weight (LBW), body weight after feathering (BWF) and weights of feather (FW), liver (LW), lung (WL) and heart (HW) and gene expression ratios or responses (GER) in Lohmann Brown–Lite (LB), Benha line (BL) and Fayoumi (F) chickens. The expressions of heat-stress associated genes (HSPH70, HSP25, HSPH1, BAG3, RB1CC1, ID1, and PDK4) were evaluated in LB, BL and F chickens exposed to 21, 32, 36, and 40°C and fed diet containing feed additives of 40% turmeric (Curcuma longa), 40% cinnamon (Cinnamomum zeylanicum), and 20% Licorice (Glycyrrhiza glabra). Three levels of DFA (zero, 2.5 and 5.0 g per kg of diet) were used. Three hundred hens of 200 days old were housed in an acclimatization chamber (100 hens from each strain). The molecular analyses including RNA extraction and Real-time quantitative PCR were used to assess the expressions of the seven investigated genes. BL chickens exhibited the highest LBW (1649 g) and BWF (1579 g) since BL chickens are significantly surpassing F chickens (1437 g vs 1388 g) and LB chickens (1556 g vs 1466 g). BL chickens had the heaviest FW (90.2 g), while F chickens recorded the lowest BWF (1388 g). The liver for all strains recorded the lowest LW (40.0 g) with the lowest HW (7.0 g). LBW, LW and HW were decreased significantly as DFA increased. The GER related to heat stress varied significantly among the three strains studied where F chickens showed the highest GER for HSP1 and ID1 genes compared to LB and BL chickens. BL chickens have shown more noticeable significant rises in GER of HSP70 and HSP25 genes. Local strains of BL and F chickens had higher GER for HSP70, HSP25 and HSP1 genes than that for the commercial BL chickens. HSP70 and HSP25 as heat-shock protein genes are showing peak GER at 40°C across all LB, BL and F strains. RB1CC1 and BAG3 as apoptosis and cell deaths genes are negatively regulated their expressions at 32 and 36°C. PDK4 gene expression decreased at intermediate temperatures of 32°C and 36°C. The GER of ID1 gene was significantly decreased as HST increased from 32 up to 40°C. The interactions effects of strain × HST had significant effect on RT, LBW, BWF, FW, LW, WL and HW in BL, LB and F chickens where BL chickens exposed to 32 or 36oC were higher in LBW, BWF, LW, WL and HW relative to LB birds. Birds exposed to 36oC and fed diet without supplementation were significantly higher in LBW, BWF, FW, LW and HW relative to the birds exposed to 40oC and fed diet containing 5 g of DFA per kg of diet. Birds of LB, BL and F chickens exposed to 32oC or 36oC and fed diet supplemented with 2.5 to 5 g of DFA per kg of diet were significantly higher in GER of HSP70, HSP25, HSP1 and PDK4 genes relative to the birds exposed to 40oC and fed the same diet.