Nanoparticles in Feed: a Potential Approach for Mitigating Heat Stress on Broilers
2022 Volume 10 Pages 328-336
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2022 Volume 10 Pages 328-336
A major environmental stressor for the poultry industry is heat stress, which results in substantial economic losses. Heat stress has recently garnered increasing public awareness and concern for its adverse effects on poultry welfare. Several physiological changes happen under heat stress, including oxidative stress, acid-base imbalance, and immunosuppression, leading to increased mortality and decreased feed efficiency, body weight, feed intake, and egg production. Reduced nutrient intake is a significant contributor to the reduction in growth performance in heat-stressed animals, perhaps because they consume less feed to reduce heat production. Hence, heat stress can be attenuated in poultry using several different strategies, each with varying degrees of effectiveness. Nanotechnology strategies have gained more attention and are found to reduce heat stress’s detrimental effects. Nanotechnology focuses on creating materials with nano-sized particles that have improved physical, chemical, and biological properties. Also, nanotechnology can be used in poultry production to improve the ability of birds to absorb nutrients and, in turn, increase growth performance, nutrient digestion, and productivity. Therefore, this review provides scientific evidence regarding the adverse effects of high ambient temperatures on poultry health and performance and potential nanoparticle approaches to mitigate those detrimental effects and their challenges.
Poultry production has been adversely affected by increasing environmental temperatures and has been identified as a considerable stressor [1, 2]. Poultry birds are highly susceptible to heat stress that reduces fertility, growth, egg production, lowers the quality of meat and eggs, and increases mortality [3]. In addition, hyperthermia induces the production of reactive oxygen species (ROS). The excessive production of ROS disrupts the balance between oxidation and antioxidant defenses, resulting in lipid peroxidation, protein oxidation, and DNA damage [4]. Damage of this nature is related to apoptosis, diseases, impaired muscle membrane integrity, and decreased performance in poultry [5]. Because of these considerations, there are various strategies to mitigate the adverse effects of heat stress on animals, among them nanotechnology. Nanotechnology has rapidly expanded in many scientific fields, and the nanoscale exhibits attractive properties such as small size, large surface area, highly active surfaces, high catalysis efficiency, and vast adsorption capabilities [6]. By increasing nanoparticle surface area, nanoparticles have the potential to interact efficiently with the body, and their increased retention time in the gut and the reduction of intestinal clearance mechanisms may result in improved bioavailability and function [7]. Thus, nanoparticles can improve growth performance, meat quality, digestion and metabolic or antioxidant enzymes, and mineral content in different tissues under physiological stress [8]. In the poultry industry, nanoparticles smaller than 100 nanometers, such as Ag, Se, Cu, Zn, and others, have been used [6, 7, 9]. According to our knowledge, no review has been performed to assess the positive effects of mineral nanoparticles in the poultry industry under heat stress. This review summarizes the detrimental effects of heat stress on birds and the impact of nanoparticles on mitigating the adverse effects of environmental stressors on poultry growth, immune functions, and antioxidant capacity, especially under heat stress conditions. Additionally, it provides novel insights into the influence of nanoparticles on the productive and physiological characteristics of domesticated birds and their challenges.
The chicken is highly susceptible to heat stress (HS) and has a narrow thermal comfort zone [10]. Poultry birds are sensitive organisms that experience environmental stress due to global warming [11]. In light of this, heat stress (36 °C) applied for ten days from the 21 to the 42 days of life, negatively affected broiler performance parameters [12]. A chicken affected by HS has significantly compromised growth rates and feed intake due to intestinal inflammation and injury, pathophysiological changes, indigestion, loss of absorption surface area, and compromised intestinal integrity, making it more susceptible to infectious diseases [11]. Heat stress reduces blood flow in the intestine, causing peripheral circulation to increase, leading to hypoxia, disrupting tight junctions, and increasing intestinal permeability, resulting in an increase of circulating endotoxins [13, 14, 15]. Besides, high temperatures cause disturbances in the acid-base balance in the blood because of hyperventilation, which causes the birds to exhale excessive amounts of CO2. A low blood CO2 level raises blood pH, resulting in a reduction in the amount of Ca2+ ions in the blood used by the shell gland, resulting in poor egg quality [16]. Bird breeders’ reproductive abilities can also be affected by heat stress since it decreases the synthesis of follicle-stimulating hormone, luteinizing hormone, and estradiol hormones. Consequently, this leads to low follicle dominance, poor egg quality, a low fertility rate, a lower hatchable rate, and a reduced number of live hatchlings [17].
Physiologically, the growth hormone receptor (GHR) and liver insulin-like growth factor I (IGF-I) expression levels are decreased under heat stress, resulting in reduced muscle growth and increased energy mobilization. High-temperature broilers also exhibit lower plasma growth hormone (GH) concentrations [18]. Heat stress can also lead to diminished dietary digestibility, lowered plasma protein and calcium levels, and the immune response [4, 19]. There has also been a reduction in the intraepithelial lymphocyte count and IgA-secreting cells in the intestinal tracts of laying hens under heat stress. Additionally, heat-stressed broilers showed a reduction in macrophages that perform phagocytosis, as well as reductions in macrophage basal and induced oxidative burst [20]. According to Awad et al. [14], heat stress reduces relative lymphoid weight in both broilers and laying hens and reduces total circulating antibodies in broilers. Consequently, heat stress lowers both primary and secondary humoral responses, as it decreases antibodies (IgG and IgM) in the blood [21].
The formation of ROS is another effect of heat stress, which damages proteins, DNA, phospholipid membranes, and other macromolecules, causing lipid peroxidation and cellular disruption [2, 22]. A depressed mitochondrial respiratory chain leads to ROS produced at a rate that exceeds the capacity of the cell to neutralize them [2]. The increased oxidative stress associated with thermal stress induces inflammatory responses in the body and lowers feed intake and growth rate, thus leading to economic losses [5]. Additionally, calcium sensitivity is affected by ROS that oxidizes thiol groups in ryanodine receptors, causing damage to an enzyme called SERCA (Sarcoendoplasmic reticulum Ca+2-ATPase). This enzyme removes excessive calcium from the sarcoplasmic reticulum to maintain calcium balance. A result of ROS is that the calcium-regulating system collapses, causing muscle contractions to overpower, resulting in muscular dystrophy [2].
Besides, exceeding the thermoneutral range of ambient temperature is one of the most lethal stressors for raising poultry [23]. As the ambient temperature increases, chicken broiler weight gain, growth, egg production, and quality are reduced, and the immune response is suppressed [14, 24]. As a result, HS reduces egg production and meat production in the poultry, resulting in severe losses for the industry [1]. Poultry industries suffer considerable economic losses due to heat stress every year [4, 19]. Despite advances in the construction and design of animal housing facilities and cooling technologies, heat stress can still severely affect animal production [25]. Broiler chickens’ growth performance is significantly depressed by high ambient temperature, so several strategies have been developed to alleviate that effect [22].
To minimize the impacts of high temperatures on poultry, several strategies are performed, including housing [26], environmental [27], feeding and nutrition [28]. Despite this, the effectiveness of these interventions has been variable or unequal due to age, breed, gender, and geographical location [27]. Shelter, shading, ventilation, and sprinkler systems are among the management strategies [29]. A typical tropical building is an open-type, naturally ventilated building oriented east west. These houses, however, are costly to build and operate in developing countries [15]. In this sense, adding tranquilizers (aminazine) and nutritional manipulations using electrolytes (minerals, oils, vitamins) could help negate the detrimental effects of heat stress acting on birds during transportation [30]. Unfortunately, the administration of drugs to animals that are being transported increases the risk of meat containing drug residues [31]. Broilers exposed to heat stress express higher selenoprotein levels, which increases their selenium (Se) requirement. This metal can inhibit the harmful effects of heat stress and maintain the efficiency of antioxidant defense mechanisms [32]. According to Lee et al. [33], elemental Se is an essential co-factor in activating the enzyme 5’deiodinase. This enzyme contributes to the formation of triiodothyronine (T3), a critical factor in controlling an animal’s energy and protein absorption, thus influencing its growth. Selenium is essential for the proper activity of glutathione peroxidase (GSH-Px), thioredoxin reductase (TrxR), and iodothyronine deiodinase in addition to its role in antioxidant response element ARE-related synthesis of antioxidant enzymes [34]. A primary antioxidant defense is GSH-Px and superoxide dismutase (SOD), while iodothyronine deiodinase is vital to thyroid hormone metabolic function and the conversion of thyroxine (T4) to T3 [35]. Additionally, thyroid hormones and glucocorticoids mediate the acclimation response to heat stress. An increase in glucocorticoids leads to metabolic changes that mobilize or produce glucose to increase the available energy for survival in stressful situations [6].
Moreover, zinc is the second most abundant trace element to reduce the adverse effects of heat stress in poultry [19, 36] due to its involvement in numerous metabolic and physiological processes [37]. Among its many functions, zinc can contribute to the performance, meat quality, and carcass traits in broilers [38], the regulation of the immune system, oxygen-free radical scavenging, and antibacterial activity [36, 39]. Similarly, zinc supplementation decreased both the detrimental symptoms of cold and heat stress [40]. In light of the above, selenium and zinc are essential trace elements that contribute to many of the body’s physiological functions in poultry. The antioxidant properties of these elements can protect cells from oxidative stress [35].
In spite of these benefits, trace minerals are still beneficial in small amounts due to their bioavailability and antagonistic effects [41]. Moreover, mineral imbalances can cause acid-base disorders affecting many metabolic functions, thereby the well-being of broilers [42]. The dual feeding system is designed to give birds access to feed at any time of the day. This approach, however, is not able to improve growth and feed efficiency in birds under heat stress [15]. Hence, nanotechnology can serve this purpose since it is a rapidly evolving technology with tremendous potential and a wide range of possible applications [43].
A nanoparticle is defined as a particle with an average diameter between a nanometer and a hundred nanometers. Nano means “very small” since 1 nanometer (nm) is equivalent to 10-9 meters (m) [44]. There are many unique properties of nanoparticles (NPs), which include their large surface-to-volume ratio, higher surface reactivity, stability, bioactivity, and bioavailability [43]. Soluble nanoparticles have more cellular influence than insoluble nanoparticles. While adsorption is a cellular influence for insoluble nanoparticles, soluble nanoparticles have profound cellular effects that depend strongly on the amount and kind of metal released. The uptake of metal oxide nanoparticles by cells also has a cellular influence [45]. They exert their mechanisms mainly by increasing the surface area for higher surface interaction and biological support, extending the residence time in the gastrointestinal tract (GIT), reducing gastrointestinal clearance mechanisms, increasing tissues’ penetration and distribution, by efficient cells uptake and delivery to target sites, as well as by increasing uptake and distribution of molecules for efficient bioavailability [46]. There are currently applications of nanotechnology in agriculture, infection control, and biomedicine [44].
Nanoparticles are used in many applications related to animal production by adding or loading them into various compounds like nutritional supplements and vaccines because of their large surface area relative to volume and high absorption [47]. Numerous studies focused on using nanoparticles to alleviate the adverse effects of high temperatures in the poultry industry. Mahmoud et al. [4] showed that nano-selenium supplementation at 0.3 mg/kg diet improved broilers’ growth performance by improving antioxidative and immune functions. The benefits of nano-Se include high absorption rates, security, antioxidant capacities, high egg-laying capacity, and high growth efficiency [48]. As reported recently by Jamima et al. [49], the addition of selenium nanoparticles (SeNPs) at a level of 0.15 mg/kg of feed improved the weight gain, live body weight of broilers, and the production performance of the broilers. The supplementation of NanoCrPic (Chromium (III) picolinate nanoparticles) to broilers exposed to heat stress at levels of 1.500 ppb (0.129 mg/mL) enhanced growth performance, organ weight, and immune function [11]. In this context, Hajializadeh et al. [50] demonstrated that supplementing Ross 308 broilers with nanochromium at a level of 1000 ppb improved performance and antibody production under heat stress conditions. In a study conducted by Abbasi et al. [9], broilers supplemented with 0.5 % silver nanoparticles Ag NPs kept a higher feed conversion ratio under heat stress. Ag NPs have also been used to promote growth in broiler chickens’ drinking water [51]. Ramiah et al. [10] showed that broilers fed dietary supplements containing 40 mg/kg and 60 mg/kg zinc oxide nanoparticles (ZnONPs) showed enhanced growth performance and antioxidant responses in the face of heat stress. Furthermore, copper oxide nanoparticles (CuO-NPs) at a concentration of 50% are used in two commercial broilers, Ross 308 and Cobb 500, to alleviate chronic heat stress-induced degenerative changes. These nanoparticles significantly improved the growth performance and strengthened resistance to the adverse effects of elevated temperatures, especially in HS birds [52].
Nevertheless, nanotoxicology is also an important term to mention, since it concerns the study of toxicity and side effects of using nanoparticles [43]. Increasing attention has been paid to the assessment of nanoparticle risks [45]. The NPs cause toxicokinetic problems mostly because they are small size, high surface to volume ratio, chemical composition, surface reactivity, functional groups, solubility, and aggregation behavior [53]. According to Schrand and colleagues [54], the toxicity of metal-based nanoparticles increases with decreasing size. As NPs bind to proteins and enzymes, they stimulate the production of ROS and result in oxidative stress. ROS accumulation leads to mitochondrial degeneration and apoptosis [55]. Nanoparticles may pose an increased risk of bioavailability, induced ROS in the inflammatory digestive diseases, and possible alteration of nutrient bioavailability by disrupted processing of protein and enzymes [56]. Almost all tests to assess NP’s toxic effects on animals revealed strong effects on various organs (liver, kidneys) and the immune system [57]. There has been evidence of ZnO NP toxicity in mammalian cells, such as membrane injury, DNA damage, and cell death [58]. The addition of zinc oxide nanoparticles (ZnO NP) to broiler diets is recommended at dose levels not exceeding 10 ppm/kg diet in the summer season to prevent heat stress hazards [59]. Besides, supplementing chicken broilers with 1.20 mg kg–1 selenium (Nano-Se), a wider spectrum of the optimal and toxic dietary levels is seen with Nano-Se as compared to sodium selenite [60]. A Cu-NP agent is an organic compound that suppresses bacterial, fungal, and viral action. Nonetheless, their size may play a role in their toxicity by facilitating cellular uptake and translocation of the particles in the animal’s body [61]. In broiler diets, nano-iron (12.22 nm) at a concentration of 4 mg kg-1, however, is highly absorbed, which can lead to detrimental effects [62]. However, the potential of nanotechnology in the poultry industry is not yet fully explored due to insufficient knowledge and research in this field. Further research is necessary to confirm the positive effect of nanoparticles that can be applied to alleviate heat stress and to observe their efficiency and cost-benefit in the poultry industry. Figure 1 summarized the adverse effects of high ambient temperatures on poultry health and performance and potential nanoparticle approaches to mitigate those detrimental effects.
Figure 1: Adverse effects of high ambient temperatures on poultry health and performance and potential nanoparticle approaches to mitigate those detrimental effects
Heat stress is one of the biggest challenges in poultry production. Poultry industries face heat stress as a prevailing threat that should be resolved to prevent losses in economic terms and to improve bird welfare. Numerous techniques are employed to reduce temperature variations in the poultry industry. Advances in technology and the effective implementation of nanotechnology allow a rapid understanding to face these challenges with greater efficiency. The application of nanotechnology reduces heat stress’s detrimental effects by enhancing broiler weight gains, egg-laying capacity, and quality of eggs and meat, reducing oxidative stress and enhancing immunity. However, the potential of nanotechnology in the poultry industry is not yet fully explored due to insufficient knowledge and research in this field. Further research is necessary to confirm the positive effect of nanoparticles that can be applied to alleviate heat stress and to observe their efficiency and cost-benefit in the poultry industry.
