There is a wealth of data acknowledging that elevated environmental temperatures adversely affect broiler productivity through decreased performance and feed intake (FI) (Emami et al., 2021; Flees et al., 2017), immunosuppression (Ghazi et al., 2012; Jahanian and Rasouli, 2015), and increased mortality (Liu et al., 2020). Selection for rapid growth and muscle development has inadvertently increased the susceptibility of the modern broiler to environmental challenges, due to greater metabolic activity, higher body heat production, and decreased thermotolerance (Deeb and Cahaner, 2002). In fact, it is estimated that the amount of metabolic heat produced by the modern broiler has increased by 30% over the last 20 years (Vizzier Thaxton et al., 2016). With projected increases in overall temperatures associated with global warming, as well as more frequent and intense heat waves (Mora et al., 2013), heat stress (HS) is one of the most pressing threats to the poultry industry (Stillman, 2019). Coupled with the need to provide a high-quality animal protein source to a growing world population (United Nations, Department of Economic and Social Affairs, Population Division, 2017), not only maintenance of the status quo, but improvements in poultry productivity and sustainability are of utmost importance. Numerous genetic, managerial, and nutritional strategies have been proposed to help mitigate the negative consequences of HS in broilers, however without mechanistic understanding, the effectiveness of these strategies is likely sub-optimal.

One promising nutritional strategy is the supplementation of plant products or extracts that exert additional benefits beyond that of simply dietary requirements. The use of medicinal plants as feed additives to boost development and health is becoming increasingly common around the world (Salem et al., 2022), not only in human heath, but within the agricultural sector as well. Though used in traditional medicine for centuries, the term “adaptogen” was first introduced by Nikolay Lazarev in 1947, when he described the effects of 2-benzyl-benzimidazol against damage to the nervous system, and its ability to increase nonspecific resistance to adverse stimuli (Brekhman and Dardymov, 1969). Based on more recent research, adaptogens can be defined as natural compounds or plant extracts that increase adaptability and survival of living organisms to stress (Panossian et al., 2018). The adaptogenic response is influenced by a wide range of factors, including its physical, chemical, and biological properties, and thereby understanding its mode of action is quite complex. In many cases, there is also evidence for a biphasic dose-effect response where at low doses they function as mild stress-mimetics, which activate the adaptive stress-response signaling pathways to cope with more severe stress (Panossian et al., 2021). However, rigorous investigation of adaptogen use in the poultry diet is lacking.

Previously, we showed that supplementation of an herbal adaptogen, NR-PHY-30 (Natural Remedies, Bengaluru, India), partially mitigated the negative effects of HS on body weight and feed intake (FI) in broilers. As feed intake is controlled at the hypothalamic level (centers of hunger and satiety) by various neuropeptides, which are potent neurotransmitters that stimulate (orexigenic) or inhibit (anorexigenic) appetite (for review see Dridi, 2022), we sought therefore to determine here the effects of adaptogen on the expression of feeding-related hypothalamic neuropeptides as potential underlying mechanisms for its beneficial response.