Heat Stress and Feed Restriction Distinctly Affect Performance, Carcass and Meat Yield, Intestinal Integrity, and Inflammatory (Chemo)Cytokines in Broiler Chickens

Abstract

This study was conducted to distinguish the effects of heat stress (HS) and feed intake (FI) on broiler chicken’s physiological responses. Day-old male Cobb 500 broilers (n = 672) were allocated to three treatments: (1) control (CTL): birds raised under normal temperature (23°C) from day 29 to 42; (2) cyclic heat stress (CHS): birds exposed to high temperatures (8 h/day at 35°C; from 9:30 am to 5:30 pm) from day 29 to 42; (3) pair-fed (PF): birds raised under thermoneutral condition but fed the same amount of feed as CHS from day 29 to 42. On day 42, 15 birds/pen were processed, to measure carcass and meat yields. To measure blood parameters and gut integrity (using fluorescein isothiocyanate-dextran), on day 42, CHS birds were sampled before (Pre-CHS) and 2 h after (Post-CHS) the temperature increased. Furthermore, after sampling CTL birds, they were exposed to 2h heat and sampled (acute heat stress, AHS). Data were analyzed using one-way ANOVA (JMP Pro15) and significance between treatments identified by LSD (P < 0.05). BW and relative carcass yield were significantly higher in CTL compared to CHS and PF. Compared to CHS, PF had significantly higher BW and lower relative carcass yield. Breast yield was significantly higher for CTL and PF, while leg quarters and wings yield were significantly lower compared to CHS. Gut barrier integrity was significantly altered in Post-CHS and AHS compared to CTL. mRNA abundances of tumor necrosis factor-α, C-C motif chemokine ligand-20, heat shock protein (HSP)-27, and HSP70 were significantly higher in Post-CHS and AHS compared to CTL. AHS had significantly higher mRNA abundances of CARD domain containing (NLRC)-3 and NLRC5 inflammasomes, and lower superoxide dismutase (SOD)-1 and SOD2 abundance compared with CTL. PF had significantly higher liver weight (% BW) compared to all other groups; while abdominal fat was significantly higher in Pre-CHS compared to CTL, PF, and AHS. Together, these data indicate that the negative effects of HS are partially due to reduced FI. However, the negative effect of HS on gut integrity, average daily gain, feed conversion ratio, and meat yield are direct and independent of the reduced FI during the HS. Thus, warrant investigating the underlying mechanisms in future research.

Effects of Cyclic Thermal Stress at Later Age on Production Performance and Meat Quality of Fast-Growing, Medium-Growing and Thai Native Chickens

“…In the study of Emami et al [ 9 ], broilers were exposed to 35 ± 1 °C for 8 h during the age of 29 to 42 days, while the control broilers were kept at 23 °C. Shao et al [ 36 ] applied a similar thermal condition to that used in the study of Emami et al [ 9 ] and reported significant decreases in body weight gain and feed intake in Chinese yellow-feather broilers exposed to the challenge. Souza et al [ 5 ] showed that nutrient utilization and energy metabolism of broilers were not affected by a cyclic thermal exposure (32 °C, 8 h daily).…”

“…Duangjinda et al [33] compared the growth performance of broilers and Thai NT chickens under either thermoneutral (26 • C) or chronic thermal stress (36 to 38 • C, 6 h daily) for three weeks and reported the thermal-induced suppression of growth performance for BR but not in the NT chickens. In the study of Emami et al [9], broilers were exposed to 35 ± 1 • C for 8 h during the age of 29 to 42 days, while the control broilers were kept at 23 • C. Shao et al [36] applied a similar thermal condition to that used in the study of Emami et al [9] and reported significant decreases in body weight gain and feed intake in Chinese yellow-feather broilers exposed to the challenge. Souza et al [5] showed that nutrient utilization and energy metabolism of broilers were not affected by a cyclic thermal exposure (32 • C, 8 h daily).…”

“…Their feathers work as thermal insulation, preventing heat dissipation, and their body parts that are not covered by feathers are in a smaller proportion. In this regard, when they encounter thermal stress, broilers reduce their feed intake and physical activities to minimize metabolic heat production, compromising body weight gain and overall broiler production performance [ 4 , 5 , 6 , 7 , 8 , 9 ]. Recent studies unraveled the events of disturbed metabolic homeostasis, altered antioxidant capacity and hormonal system and impaired gut integrity in the broilers exposed to experimental thermal stress condition [ 2 , 4 , 8 , 9 ].…”

“…In this regard, when they encounter thermal stress, broilers reduce their feed intake and physical activities to minimize metabolic heat production, compromising body weight gain and overall broiler production performance [ 4 , 5 , 6 , 7 , 8 , 9 ]. Recent studies unraveled the events of disturbed metabolic homeostasis, altered antioxidant capacity and hormonal system and impaired gut integrity in the broilers exposed to experimental thermal stress condition [ 2 , 4 , 8 , 9 ]. In addition, properties of the meat, in terms of chemical composition, pH, water-holding capacity and texture, were deviated when the animals were exposed to heat stress [ 10 , 11 , 12 ].…”

Meta-Analysis and Systematic Review of the Thermal Stress Response: Gallus gallus domesticus Show Low Immune Responses During Heat Stress

“…There are many studies that have revealed the effect of heat stress on broiler growth performance, including mass gain, feed intake, and feed conversion ratio (He et al, 2020;Emami et al, 2021). Broilers are highly heat stress-sensitive (Nassar and Elsherif, 2018) and lose their immune system function, which leads to death (Hirakawa et al, 2020).…”