Exposure of broiler chickens to chronic heat stress increases the severity of white striping on the pectoralis major muscle

Abstract

A study was conducted to evaluate the effect of cyclic or chronic heat stress (HS) on the incidence and severity of white striping (WS) and histopathological changes in breast muscle of broiler chickens. One hundred eighty 1-day-old male chickens were randomly assigned to three research groups: control (standard temperature throughout the experiment), cyclic HS (32 ºC between 0800 and 2000 h from day 21 until the end of the experiment), and chronic HS (32 ºC from day 21 onwards). Cyclic and chronic HS groups showed a significant (P < 0.05) decrease in body weight gain and feed intake and poor feed conversion ratio in grower, finisher, and overall period. Serum biochemical profile was not different among the groups except globulin and P which were significantly higher (P < 0.05 and P < 0.001, respectively), in cyclic and chronic HS groups. Overall, WS incidence was numerically higher in control birds followed by chronic HS and cyclic HS birds, respectively. The chronic HS group had a lower incidence of mild (score 1) and a higher incidence of severe (score 2) WS lesions compared to control and cyclic HS groups. Histopathological analysis revealed that broilers subjected to chronic HS showed increased severity of myodegenerative changes, perivenular CD3 + cell infiltration, and lipidosis compared to control group. However, control and cyclic HS groups were not different in terms of histopathological lesions. In conclusion, this study confirms that cyclic or chronic HS may adversely affect the growth performance and that chronic HS may increase the severity of WS in broiler chickens.

Influences of Thermal Stress During Three Weeks Before Market Age on Histology and Expression of Genes Associated With Adipose Infiltration and Inflammation in Commercial Broilers, Native Chickens, and Crossbreeds

“…This hypothesis was in agreement with previous reports of Kuttappan et al (2013a) and Malila et al (2018) that the high degree of WS and WB was significantly related with heavier birds and pectoral muscle yield. In accordance with our current findings, a recent study of Aslam et al (2021) showed that Arbor Acres broilers received cycle heat stress (32°C, 12 h daily, 21–42 days) exhibited reduced body weight gain with less cases of WS in comparison to the birds raised under control condition (22–24°C).…”

“…On the contrary, the CB chickens exposed to the thermal stress were affected with adipose infiltration at a lesser extent than control CB. The current results were in congruence with the report of Aslam et al (2021) in which less incidence and severity of myodegeneration, inflammatory and lipid infiltration, and fibrosis were observed in the pectoralis major muscle collected from Arbor Acres Plus broilers exposed to cyclic heat stress compared to the birds reared under thermoneutral condition.…”

“…An ambient temperature above 30°C is considered sufficient to induce stress among the birds ( Azad et al, 2010 ; Adu-Asiamah et al, 2021 ). The negative impacts of thermal challenge include diminished growth performance ( Azad et al, 2010 ; Quinteiro-Filho et al, 2010 ; He et al, 2018 ; Aslam et al, 2021 ), increased mortality ( Al-Fataftah and Abdelqader, 2014 ), compromised gut health, ( Quinteiro-Filho et al, 2010 ; Awad et al, 2020 ), and deviated meat quality ( Sandercock et al, 2001 ; Lu et al, 2017 ; Malila et al, 2021a ). A recent meta-analysis performed by Andretta et al (2021) highlighted that broilers with increasing age and weight become more sensitive to heat as their heat dissipation area becomes smaller.…”

“…The cyclic thermal stress, resembling the daily rise of temperature in the tropical region or in the summer of the temperate zone, exerted adverse impacts on growth performance of commercial broilers, although the impact was at a lesser extent than that of the constant heat challenge ( Souza et al, 2016 ; Aslam et al, 2021 ). Under cyclic stress, commercial broilers are partly able to adjust to the stressed environment and have compensatory gain during the non-stressed period ( Aengwanich, 2007 ; Andretta et al, 2021 ).…”

“…Heat stress may exert a negative impact on meat quality through oxidative damages ( Lu et al, 2017 ). This could impair the muscle regeneration process and lead to muscle abnormalities, including emerging myopathies known as white striping (WS) and wooden breast (WB), among the chickens exposed to thermal challenge ( Aslam et al, 2021 ). Several studies indicated chemical changes, that is, reduced protein and increased fat content in chicken meat affected with those abnormalities ( Kuttappan et al, 2012 ; Petracci et al, 2014 ; Malila et al, 2018 ; Thanatsang et al, 2020 ).…”