Journal of Thermal Biology 90 (2020) 102573 Available online 21 April 2020 0306-4565/© 2020 Elsevier Ltd. All rights reserved. Dietary curcumin supplementation effects on blood immunological profle and liver enzymatic activity of laying hens after exposure to high temperature conditions Aamir Nawab 1 , Shuyan Tang 1 , Guanghui Li, Lilong An * , Jiang Wu, Wenchao Liu, Mei Xiao Department of Animal Science, Agricultural College, Guangdong Ocean University, Haida Road, Mazhang District, Zhanjiang, 524088, Guangdong, China A R T I C L E INFO Keywords: Blood immune profle Curcumin Heat stress Laying hens Liver enzymatic function ABSTRACT Various environmental factors affect livestock production but heat stress is a major challenge in the poultry farming. Poultry exposes to high temperature alters blood immunological parameters and liver enzymatic function which in turn, suppress the immunity and disease resistance of chickens. Thus, the purpose of present study was to explore the effect of dietary curcumin supplementation on blood immunological biomarker and liver enzymatic activity of laying hens under heat stress conditions. Experimental groups contained two control groups (normal temperature control (NC) and heat stress control (HC) and 3 heat stress curcumin treatment groups (HT100, HT200 and HT300). Hens in HC group with basal diet and heat stress curcumin treatment groups were exposed 6 h/day heat stress (32 � 1 � C) from 10:00 a.m. to 16:00 p.m. for 9 week. The results of present study showed that heat stressed curcumin treatment group had improved liver weight, WBC values and immunoglobulin level as compared to untreated HC and NC groups. The available results also indicated that laying hens supplemented with curcumin under high temperature conditions had reduced H/L ratio, serum corticosterone levels, infammatory cytokines response and liver enzymatic activity (ALT) which enhanced the immunity of laying hens under hot climatic conditions. Therefore, it is concluded that curcumin has ability to combat harsh environmental conditions which can be used as anti-infammatory and immune booster feed ad- ditive in the poultry nutrition. 1. Introduction Poultry farming has performed a leading role in the livestock sector in some parts of the world (Leinonen et al., 2014; Sebho, 2016; Nawab et al., 2018a,b,c), but increasing temperature has deleterious effect on poultry production especially during the hot and humid conditions (Nawab et al., 2018a,b,c). Poultry requires suitable environmental and managemental conditions for optimum production. When temperature increases above the thermoneutral zone, birds experience heat stress (Nawab et al., 2018a,b,c). High temperature negatively affects the blood immunological biomarkers and liver enzymatic function of chicken (Honda et al., 2015; Nawab et al., 2018a,b,c). Blood immune cells indicate the immune status of chickens that should be examined under high temperature conditions. Liver performs signifcant role in the activation of specifc and non-specifc immune responses because it is sensitive to environmental stress, toxins, food antigens and bacterial components (Gao, 2016). High temperature causes oxidative damages in the liver tissues and suppress the immune responses which in turn, reduce the disease resistance of laying hens (Shini and Kaiser, 2009; Shini et al., 2010; Nawab et al., 2018a,b,c). Generally, stress is associated with higher plasma level of corticosterone. Corticosterone is responsible for several changes in immune function. High blood corticosterone level disturbs heterophil/leukocytes (H/L) ratio and dysregulate immune function which can enhance pathogenic challenges in chickens (Quinteiro-Filho et al., 2010; Shini et al., 2010; Calef et al., 2014). Dietary manipulation is one of the alternative methods to improve the blood immunological biomarkers and liver function of poultry birds under harsh temperature (Nawab et al., 2018a,b,c). Several studies have reported that plant substances in animal nutrition provide benefcial effects by improving immune responses, enzymatic activities and antioxidant metabolites (Ledoux, 2009; Toghyani et al., 2011; Nawab et al., 2018a,b,c). * Corresponding author. E-mail address: anlilong@126.com (L. An). 1 These two authors (Aamir Nawab, Shuyan Tang) have equal contribution in this paper. Contents lists available at ScienceDirect Journal of Thermal Biology journal homepage: http://www.elsevier.com/locate/jtherbio https://doi.org/10.1016/j.jtherbio.2020.102573 Received 13 December 2019; Received in revised form 4 March 2020; Accepted 16 March 2020