Poultry production has one of the fastest rates of development among animal industries, and it greatly enhances nutrition and food security. Over the past few years, broiler chicken genetics, feed conversion ratio, fat reduction and breast size, as well as egg production and quality, have all seen considerable improvements
[1,2,3][1][2][3]. In the poultry industry, the cost of feed makes up a sizeable amount of the total cost of producing meat and eggs. The general condition of a chicken’s health, especially the gastrointestinal tract (GIT), plays an important role in the final cost of the product. The GIT of the birds is exposed to a variety of factors through feed and environment, which affect chicken health
[4,5][4][5]. The main environmental pollution entry points for undesired compounds into the food chain include air, water, soil, and feed. According to Sharma et al.,
[6], heavy metals are one of the environmental contaminants that enter animal feed from natural, industrial, and agricultural sources. Lead (Pb) can be absorbed through the skin; however, it is primarily absorbed through the digestive and respiratory systems
[7]. According to the data that are now available, environmental pollution, the availability of supplements and concentrates, or the technology and equipment used during manufacturing make the heavy metal contamination of animal feeds inevitable
[8]. Health risks to both humans and animals can result from hazardous compounds including cadmium (Cd), Pb, and arsenic (As) entering the food chain
[9]. Pb is neurotoxic and can harm hemopoiesis, renal function, the nervous system, and the gastrointestinal system in addition to impairing metabolism
[10]. Pb distribution in the body first depends on blood flow into various organs, while about 95% of Pb is deposited in skeletal bones as insoluble phosphate
[11]. Due to the fact that it comes from the environment and various dietary sources, the diet could be a source of Cd pollution
[10]. Cd is then transferred from other animals to people through the food chain, where it damages the lungs, liver, and kidneys and causes hypertension
[8]. According to one study, broiler meat products (e.g., burgers and frankfurters) had higher levels of Cd, Cu, Mn, Ni, Pb, and Co compared to raw meat and table eggs
[12]. Overall, the findings demonstrated that eating chicken meat products posed a health risk to consumers since Pb and Ni levels were four and seven times higher than the permitted maximum limit, respectively, while the levels of Pb and Ni may vary from a country to a country. Additionally, even in very low amounts, arsenic is a highly hazardous element in feed and drinking water. The hazardous dose of As for poultry is between 40 and 50 mg/kg of chicken feed; at 40 mg/kg, egg production is reduced, but at 50 mg/kg, feed consumption is reduced
[13]. Heavy metals are one of these elements; when they interact with the chicken’s body, they create free radicals. If there are too many of these reactive oxygen species/reactive nitrogen species (ROS/RNS), a type of unstable molecule that contains oxygen/nitrogen and that easily reacts with other molecules in a cell, the DNA, protein, and lipid structures, this may harm and impair cell function (
Figure 1). At specific concentrations, both ROS and RNS function as homeostasis-related signaling molecules. Oxygen metabolism produces ROS, such as superoxide, hydrogen peroxide, and hydroxyl radicals, which are further balanced by the rates of oxidant generation and oxidant removal. Certain cells of the intestinal mucosa and submucosal areas express the RNS that are byproducts of nitric oxide synthases (NOS). Nitric oxide radical (NO), created when the NOS converts arginine to citrulline, is essential for cellular processes such as neurotransmission and immunomodulation. Yet, excessive NO generation harms the intestinal mucous membrane and impairs nutritional absorption. Due to the high concentration of polyunsaturated fatty acids in cell membrane lipids and lipoproteins, both ROS and RNS can contribute to lipid peroxidation. Lipid peroxidation produces 4-hydroxynonenal as its byproduct, which worsens oxidative damage to cell membranes, compromises cell signaling, causes mitochondrial dysfunction, and disturbs redox equilibrium.