Heat stress and feed restriction distinctly affect performance, carcass and meat yield, intestinal integrity and inflammatory (chemo) cytokines in broiler chickens

Authors: EMAMI, NIMA - University Of Arkansas; GREENE, ELIZABETH - University Of Arkansas; Kogut, Michael - Mike; DRIDI, SAMI - University Of Arkansas

Submitted to: Frontiers in Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2021
Publication Date: 7/22/2021
Citation: Emami, N., Greene, E., Kogut, M.H., Dridi, S. 2021. Heat stress and feed restriction distinctly affect performance, carcass and meat yield, intestinal integrity and inflammatory (chemo) cytokines in broiler chickens. Frontiers in Physiology. 12. Article 707757. https://doi.org/10.3389/fphys.2021.707757.
DOI: https://doi.org/10.3389/fphys.2021.707757

Interpretive Summary: Global climate change is a potential threat to avian species, which are highly susceptible to heat stress (HS) due to the lack of sweat glands and higher core body temperatures compared to humans. Demand for poultry meat is on the rise and expected to more than double by 2050. However, several factors, including HS, negatively impact the efforts of the poultry industry to meet the high demands by eliciting physiological, behavioral, and production changes in poultry. Therefore, evaluating the effects of HS on a bird’s physiology, immune response, and gut integrity is important, and a thorough understanding of these responses is necessary to better design targeted treatments or interventions. Heat stress slowed the growth and muscle development of chicks through their life spans compared to chicks under controlled temperatures. Interestingly, the reduced growth was not due to the chicks eating less food. Additionally, heat stress blocked the ability of the chicks to digest food and absorb nutrients in through their guts. Heat stress diminished the ability of the chicks' immune system to function normally, leaving them susceptible to possible infections. These experiments are important to the poultry industry in the U.S. and worldwide because of the need to increase poultry production to meet the protein needs of the population over the next 30 years. These experiments provide a model for us to design new intervention strategies to reduce the effects of heat stress on growing chickens.

Technical Abstract: Global climate change potentially threatens all kinds of life on earth, and increased frequency and severity of heat waves are predicted over the next few decades. Broiler chickens are particularly susceptible to heat stress (HS) due to their unique physiology and high metabolic rates. One of the most prominent effect of HS is depression of feed intake (FI). This study was conducted in order to distinguish between the effects of HS per se and FI on the broiler chicken's performance, carcass and body parts yield, immune response, and gut integrity. In total, 720 day-old male Cobb 500 broiler chicks were randomly allocated to three treatments with 8 replicates of 28 birds/pen including: 1) control (CTL): birds raised under normal temperature (23C) from d 29-42 and had free access to the diet; 2) Cyclic heat stress (CHS): birds exposed to high temperatures (8 h/d at 35C; from 9:30 am-5:30 pm) from d 29-42 and had free access to the diet; 3) pair-fed (PF): birds raised under the same condition as CTL group, but fed the same amount of feed as HS group from d 29-42. All birds were fed a corn-soybean meal basal diet. Feed and water consumption were measured daily and body weight measured weekly. On d 42, 15 birds/pen were processed and carcass parts were weighed. Mortality was similar in all the treatments during the starter, grower, finisher, and overall experimental period. Core body temperature was increased ~1C during the CHS period in the CHS group, as compared to the CTL and PF birds. Body weight (BW) and relative carcass yield was significantly higher in CTL compared to HS and PF birds, ds on d 42. Compared to CHS, PF birds had significantly higher BW and lower relative carcass yield. Body parts yield data showed significantly higher breast yield for CTL and PF, compared to CHS. In contrast, leg quarters and wings yield were significantly higher for CHS, compared to CTL and PF. FITC-d data showed that gut barrier integrity was significantly altered in Post-CHS and AHS, compared to CTL. Blood cytokine, chemokine, inflammasomes, heat shock proteins (HSP), and antioxidants analysis showed significantly higher mRNA abundances of TNF-a, CCL-20, HSP-27, and HSP-70 in Post-CHS and AHS groups compared to CTL. Together, the data indicates distinct effects of FI and HS on broiler chicken performance, body parts yield, immune response, gut integrity and organ weight.