Author:
DEEP CHAND VASHISHTHA -M.Sc , MBA
NSM- Bioncia International Pvt Ltd

Stress comes in many forms and seems to affect the performance of birds. The term “stress” is used to describe the detrimental effect of variety of factors on the health and performance of poultry (Rosales, 1994) Or “Stress is the nonspecific response of the body to any demand”, whereas stressor can be defined as “an agent that produces stress at any time”. Therefore, stress represents the reaction of the animal organism (i.e., a biological response) to stimuli that disturb its normal physiological equilibrium or homeostasis (Selye, 1976). The commercial high yielding breeds are more susceptible to stress and diseases. Stress represents the reaction of the animal organism (i.e., a biological response) to stimuli that disturb its normal physiological equilibrium or homeostasis. The importance of animal responses to environmental challenges applies to all species. However, poultry seems to be particularly sensitive to temperature-associated environmental challenges, especially heat stress. Understanding and controlling environmental conditions is crucial to successful poultry production and welfare. Heat Stress not only causes suffering and death in the birds, but also results in reduced or lost production that adversely affects the profit from the enterprise.

Heat stress or any type of Stress have side effect on Vital organs heart, brain, kidneys, liver, and lungs.
Heat Stress adverse effects on liver
The liver is pivotal organ of metabolic activity, which performs essential cellular functions containing the balance of energy metabolism, biosynthesis of vitamins and minerals, and ammonia detoxification (Schliess et al., 2014). Elevated blood flow transfers from the hepato-splanchnic region to respiratory muscles and superficial body tissues to accelerate heat dissipation and decrease body temperature under heat stress, therefore, liver is more sensitive to heat stress (Hai et al., 2006; Crandall et al., 2008). It has been reported that heat stress caused liver fat accumulation and inflammation, and impaired liver function in broiler.

Heat stress adverse effects on respiratory system
Heat stress can cause damage to the lung tissue of broiler chickens by disrupting the integrity of the blood-air barrier and increasing permeability diseases can cause different degrees of lung damage Mammals mainly rely on sweat glands to dissipate heat and maintain body temperature balance (Yahav, 2015), but poultry lack sweat glands, so they primarily dissipate heat through respiration when the temperature is too high (Bell et al., 2001). High-frequency breathing leads to increased susceptibility of lung tissue damage in a heat stress environment. Damage to the blood-air barrier can lead to increased lung permeability, impaired oxygen and carbon dioxide exchange function, and induce respiratory difficulties (Wang et al., 2020), further leading to various lung diseases such as tuberculosis and pulmonary inflammation (Research has shown that heat stress causes lung injury and results in the upregulation of various proinflammatory cytokines, including tumor necrosis factor.

Conclusion
High ambient temperature has emerged as a major constraint for the future development of the poultry industry, especially in the tropics and subtropics. The scarcity of resources coupled with harsh environmental conditions is the most crucial predicaments in the way to rationalize optimum production of broiler. Heat stress disturbs the physiological biochemistry of the broiler which ultimately reduces feed intake and feed efficiency which ultimately results in reduced performance and productivity. Under hot environmental conditions, feed utilization is disturbed by the deposition of fat and oxidative stress. In addition, changes in blood cells, acid-base balance, immune response, liver health, and antioxidant status are some of the major dynamics altered by heat stress.

Alleviating the Adverse Effects of Heat Stress is mandatory to achieve Production & performance poultry Business.

Dr.Partha P. Biswas
M.Sc.,Ph.D.,F.Z.S.,F.Z.S.I.
Former Asso. Professor & H.O.D.,
Dept. of Zoology, R.K.Mission V.C.College,
Kolkata ,W.Bengal.
Senior Consultant, Aqua-Vet inputs,
Fin-O-Wing Formulations, Kolkata-700084

The chicken industry is becoming more vulnerable to environmental shifts, particularly high temperatures. Open-sided poultry species are susceptible to heat stress, negatively impacting growth and productivity. Factors determining heat stress include temperature radiation, humidity, metabolic rate, age, and duration. Modern commercial broilers are more sensitive to heat stress, making understanding and controlling environmental conditions crucial for poultry production and health. High temperatures in birds reduce antioxidant capacity, requiring food handling and expensive cooling. Understanding and controlling environmental conditions is crucial for poultry production and health.

Thermoregulatory Device in Chicken
Unlike mammals, birds do not have sweat glands, but they have developed a number of behavioral adaptations to cope with heat, including increased breathing rate, panting and raised wings. Commercial poultry prioritize high production, making broilers more sensitive to environmental stresses, and affecting meat quality and immune problems. Under conditions of heat stress, metabolic heat increases, and the animal succumbs to hyperthermia. In summary, it can be concluded that high ambient temperature outside the thermoneutral region during the production phase has a bad effect on meat production, meat quality and causes serious immune problems in broilers.

Heat Shock Proteins of Poultry Birds During Heat Stress
Heat shock proteins (HSPs) are stress proteins found in all living organisms that are activated by high environmental temperatures to protect cells from stressors such as heat. The 70 kDa heat shock proteins (HSP70) are a family of proteins known for their potential role in thermotolerance and widely regarded as cellular thermometers. Over expression of HSP70 has been observed under oxidative stress, leading to mitochondrial reactive oxygen species scavenging and pulmonary endothelial protection against bacterial toxins. They keep cells in order by synthesizing other proteins, attract immune cells and participate in protein assembly and degradation. Higher HSP expression is associated with better heat tolerance and is produced by all living organisms in high temperature environments.

Effects of Heat Stress in Poultry Birds
Reduced voluntary feed intake which affects the functionality of the entire digestive system High environmental temperatures activate the hypothalamus–pituitary axis, brain-gut axis and elevate plasma corticosterone concentrations, affecting the digestive system’s functionality.

This leads to changes in motility, flux patterns, secretory activity, content viscosity and pH Generation of ROS (reactive oxygen species) and the efficacy of the antioxidant defense system deteriorate. Overproduction of ROS in mitochondria can damage proteins, lipids, and DNA Heat stress can impair the feeding process, nutrient absorption and utilization, although water intake increases rapidly Upregulation of adipokines secretion (leptin and adiponectin) and the expression of their receptors can negatively regulate feed intake and calorie consumption thus resulting in decreased metabolic heat production The decline in trypsin, chymotrypsin and amylase (intestinal secretion) due to reduced feed intake often results in impairment of digestive functionality, nutrient digestibility Hypoperfusion and an increase in blood flow to the skin surface occur as an adaptive response of the circulatory system to stabilize blood pressure and promote heat loss It is known that heat challenge has an immune-suppressive effect.

Use of Dietary Phytochemicals to Reduce Heat Stress
Experimental studies on poultry birds suggest phytochemical ingestion may reduce heat stress effects. These phytochemicals can directly or indirectly influence genes and metabolic pathways, with stress reduction linked to antioxidant qualities.

Fig.3: The chicken’s response to being overheated. Chickens raised in high temperatures produce more reactive oxygen species and show signs of immunological inflammation in addition to consuming less food.

Mitigating Heat Stress Using Epigallocatechin-3-Gallate (EGCG), A Secondary Metabolite in Green Tea

Green tea’s most prevalent catechin, EGCG, is thought to be its most bioactive ingredient and possesses potent antioxidant properties. The primary cause of heat stress-induced oxidative stress in poultry is damage to tissues and cells, which is mostly manifested in an increase in MDA (malondialdehyde) concentration in such tissues and cells. It has been demonstrated that adding the polyphenol EGCG to broilers housed in thermoneutral environments may increase their antioxidant capacity. Acutely heat-stressed broilers may have greater antioxidant capacity and less oxidative damage in their muscles because EGCG may activate the Nrf2 signaling pathway.

Reducing Heat Stress in Broiler Chickens With Additional Ginger (Zingiber Officinale) and Onion (Allium Cepa)

Onion and its derivatives including saponins, aglycones, quercetin, cepaenes, flavonoids, organosulfurs, and phenolic compounds showed various pharmacological properties and therapeutic effects.When broilers are heat stressed, the combination of onion and ginger supplements increases the nutrition of the groups more than no supplementation.

According to research results, growth performance, carcass quality, antioxidant levels and immune system response of broilers are improved when fed 10 g of ginger and and 2.5 g of onion during heat stress. Ginger contains substances with powerful antibacterial and antioxidant properties, including chagaol, ginger diol and ginger diol. Ginger (2%) added to broilers suffering from heat stress significantly improved blood biochemical parameters and growth indicators compared to the control group.

Seeds of Black Cumin (Nigella Sativa) improve Bird’s Ability to Live in Heat-stressed Conditions

Black cumin seeds have been shown to have pharmacological and antibacterial properties and also contain drug-like compounds. The volatile oil (0.4-0.45%) contains saturated fatty acids, which include: nigellone, which is the only component of the carbonyl fraction. oil, thymoquinone (TQ), thymohydroquinone (THQ), dithymoquinone, thymol, carvacrol, α and β-pinene, d-limonene, d-citronellol, carvacrol, t-anethole, 4-terpineol and longifolin etc. Thymoquinone improves hatchability, pos-thatching performance and antioxidant activity of thermally stressed broiler embryos. Black cumin extract has been shown in trials to reduce serum MDA levels and protect against oxidative stress.

Hot Red Pepper (HRP) Reduces Heat Exhaustion in Birds

Ascorbic acid, or vitamin C, is abundant in capsaicin, a terpenoid found in HRP that helps prevent heat exhaustion in birds. Carotenoids, which are rich in vitamins E, C, and provitamin A (beta carotene), are known to have powerful antioxidant qualities that help prevent the damaging effects of free radicals and, in certain situations, oxidative stress, which can lead to cell death in broilers. Furthermore, it has been found that adding capsaicin, an active ingredient in red pepper that is present in grill feed at a dose of 50 mg/kg, can lessen the harmful effects of heat stress.

Moringa (Moringa Oleifera)helps to Survive Birds Under Heat Stress

Moringa leaves contain high levels of total polyphenols (260mg/100g), b-carotene (34mg/100g), kaempferol (34mg/100g), quercetin (100mg/100g), as well as a total antioxidant capacity of 260mg/100g. Kaempferol and quercetin are the flavonoids present in moringa leaves and possess strong antioxidants. It has been found that 0.3% incorporation of M. oleifera leaf meal improves the performance and physiological parameters of broilers and also helped the birds survive under heat stress.

THYME (THYMUS VULGAIS) Protects Chicks Against Heat Stress

The two most important bioactive compounds in this plant are carvacrol and thymol, which may be the primary source of thyme’s pharmacological actions. Thus research has identified linalool, thymol, carvacrol, gamma-terpineol, and geraniol as the primary components of thyme. Dietary thyme essential oil (150–200 mg/kg) is more effective at shielding chicks from the harmful effects of heat stress while also enhancing immunological function and development performance. One material that may be able to improve growth in broilers located in hot climates is thyme oil.

Coriander (Coriandrum Sativum) Seed in Ameliorating the Impact of Thermal Challenges

According to research, broilers under heat stress that are fed 2% coriander seed have higher feed intake, weight gain, reduced panting, and higher levels of corticosterone. The broilers’ poor intestinal absorptive capacity and shape may be connected to the rise in corticosterone levels during stress. Furthermore, according to a different study, adding 2% coriander to the diet helps broiler birds by lessening the effects of heat shock. The supplement, according to the author, benefitted broilers that were experiencing heat stress and enhanced their blood parameters, immunity, and overall performance.

Cinnamon (Cinnamomum Zeylanicum) Powder as Antioxidant in Thermally Challenged Birds

The common herbal plant, cinnamon contains different active phenolic compounds, which include flavones, catechin, isoflavones, flavonoids and other phenolics. The main bioactive constituent of cinnamon is cinnamaldehyde. The phenolic components function as antioxidants and can effectively scavenge ROS. Cinnamon supplements help in homeostasis due to the reduced pH caused by heat stress. It has also been reported that an increase in the activity of CAT, total antioxidant capacity and SOD and a decrease in the MDA when birds were placed in a thermally challenged environment during their finishing phase.

Turmeric (Curcuma Longa) for Heat-stressed Broilers

The yellowish pigments of turmeric, namely demethoxycurcumin, curcumin, and bisdemethoxycurcumin, are commonly referred to as curcumoids. Curcuminoids are an antioxidative compound found in turmeric. Researchers have shown the effects of turmeric powder supplement at 0.3 and 0.6 g/kg when administered to birds under heat stress. The superoxide radicals are neutralized, and there is an increase in the activity of SOD and CAT (ROS-removing enzymes or antioxidant enzymes ) and a decrease in MDA in broilers. The increased level in MDA indicates oxidative damage in liver of heat stressed broilers.

Conclusion
Heat stress can hurt poultry birds by making them grow slower, weakening their immune system, causing intestinal inflammation, and causing other health problems. It can also trigger oxidative process. But using natural substances called phytogenic compounds can help chickens who are raised in hot conditions.But more research is needed to understand the molecular changes made by medicinal herbs and the interactions between their active components, gut microbiota, and gut barriers. By using these approaches, we can improve chicken welfare and make poultry production more sustainable and efficient.

It was first discovered in the juice of sugar beets. Naturally accumulated in plants as osmolyte to protect against salt and temperature stress. Derivative of glycine (amino acid). Neutral molecule with bipolar structure (zwitterion) as shown in Fig. 1 contains three methyl groups.

Fig.1: Chemical Structure of Betaine

2. Betaine functions as (mode of action):
A. Methyl donor – methyl groups used for protein synthesis and other metabolic processes. Methyl groups play a pivotal role in several cellular processes, including DNA methylation, synthesis of phosphatidylcholine, and protein synthesis. Choline and betaine are both capable of donating methyl groups. However, for choline to do so, it must first be converted into betaine as shown in Fig. 2. In poultry, the capacity to synthesize betaine from choline is limited, thus making dietary supplementation the primary source.

Fig. 2: Role of betaine in the methionine cycle in liver

Betaine can substitute for choline in performing the following functions:
1) Regulating fat metabolism in the liver to prevent abnormal fat accumulation in hepatocytes.
2) Serving as a methyl donor for the formation of methionine and creatine, through its involvement in the transmethylation pathway.
Betaine cannot replace choline in the function of maintaining cell membrane and structure as an emulsifier to transport lipids, since choline is a constituent of phospholipids. Similarly, betaine cannot replace choline as a precursor of acetylcholine in the transmission of nerve impulses.

B. Osmo-regulator: – ability to bind and retain water in a reversible manner.
Osmolytes are compounds that aid in the regulation of osmotic pressure within cells and tissues, playing a crucial role in preserving cellular integrity.
Dehydration, disease, heat stress, and other factors can cause alterations in the water content of cells. Osmolytes can be either inorganic ions such as Na+, K+, Cl-, or organic compounds such as amino acids, certain sugars, and betaine. Betaine plays a crucial role in stabilizing cellular metabolic function during periods of stress, preserving the cell’s capacity to uptake nutrients, unlike osmolytes such as Na+, K+, and Cl-. Moreover, it offers protection to intracellular enzymes against osmotic inactivation.

3. Heat stress
Heat stress is a major challenge in poultry production, especially during the hot summer months. It occurs when birds face difficulty in achieving a balance between body heat produced and heat loss. This imbalance can lead to several health issues and production losses.

4. The Role of Betaine in Enhancing Poultry Health During Heat Stress.
a) Betaine aids in preserving intestinal integrity by facilitating water retention, increasing cell volume, promoting anabolic activity, and maintaining cellular integrity as shown in fig. 4. which are Representative photomicrographs of the ileum after 10 days of the experiment from broilers fed a control diet (CON, A and C) and betaine (BET, B and D) on villous height under thermoneutral (TN, A and B) or after 10 days being exposed to heat stress (HS, C and D).

Fig. 3 – Intestinal barrier damage in HS (Soheil Varasteh, et al. Nutrients, 2020)

Fig. 4 – Impact of betaine on intestinal integrity of broiler birds in Heat stress conditions (Shakeri et al, Animals 2020)

b) Betaine has three methyl groups in its structure and donates them in various metabolic reactions, which can spare compounds like methionine, choline, and folic acid. Therefore, supplementing with betaine may reduce the need for these nutrients.

c) The growth rate of poultry birds is enhanced by betaine, which conserves energy that would otherwise be expended on the Na+/K+ pump and Calcium pump in high temperatures. This conserved energy can then be directed towards growth.

d) Betaine enhances the concentration of beneficial short-chain fatty acids, such as acetic and propionic acid, which are vital to host bacteria like Lactobacillus and Bifidobacterium in poultry. This improvement enables these bacteria to effectively inhabit the caecum and inhibit the colonization of harmful bacteria in the intestinal tract.

e) Betaine supplementation in laying hens leads to an increase in daily egg mass production, reduces thin eggshell issues which are related to heat stress, and helps to enhance serum concentrations of estradiol and melatonin.

f) Trouw Nutrition’s Betaine is proven to elevate production performance even under heat stress conditions, notably increasing breast meat percentage through the provision of essential methyl groups, as depicted in Fig. 5. Recognizing that high-performing animals demand superior nutrition for sustained health and optimal growth, Selko Feed Additives introduces TNIbetain. This meticulously tested supplement supports animal performance across multiple metabolic pathways. TNIbetain adheres strictly to the stringent quality standards upheld by Trouw Nutrition Feed Additives.

Fig. 5: Effect of Trouw Nutrition betaine on broiler performance
Contrasting the Attributes of Trouw Nutrition’s Natural Betaine with Synthetic Betaine

Recommended Dosage:
For broiler, layer, and breeder birds: 0.5 to 1 kg per ton of feed. However, in challenging conditions such as heat stress, the Betaine dosage can be increased to up to 2 kg per ton of feed.
g) Betaine has been found to significantly enhance hematological parameters, including RBC and platelet count, while reducing the number of heterophils and increasing the number of lymphocytes. The reduction in lymphocyte count during heat stress is attributed to the rise in inflammatory cytokines, which stimulate hypothalamic production of corticotrophin releasing hormones.
h) Betaine aids in the expansion of intestinal mucosa, thereby enhancing the absorption and utilization of nutrients, which results in improved digestibility of crude protein, crude fiber, ether extract.
i) Studies have demonstrated that betaine interacts with lipid metabolism by promoting the oxidative catabolism of fatty acids through its involvement in carnitine synthesis. Therefore, betaine can be utilized to increase the proportion of lean meat and reduce fat in poultry carcasses.
j) Betaine acts as an osmoregulatory in the intestine, optimizing water and salt balance within cells for efficient nutrient absorption and reducing litter moisture. It increases villus height, protecting enterocytes during challenges like coccidiosis, and strengthens the gut, reducing damage during infections as shown in Fig. A, B and C.
The various effects described above are either directly or indirectly linked to betaine’s osmoregulatory function and its role in methionine biosynthesis.
Betaine emerges as a pivotal component in poultry health management, particularly in the face of heat stress challenges. Originating from sugar beets, its molecular structure rich in methyl groups facilitates its dual function as a methyl donor and osmoregulator, essential for maintaining cellular integrity and supporting metabolic processes. Amidst heat stress conditions, Betaine supplementation showcases remarkable efficacy, preserving intestinal integrity, conserving energy expenditure, and enhancing production performance. Its multifaceted benefits extend to improvements in hematological parameters, nutrient absorption, and lipid metabolism. With its proven effectiveness and adherence to stringent quality standards, Betaine stands as a crucial asset in optimizing poultry health and performance under challenging environmental conditions, exemplifying the potential of innovative nutritional strategies in safeguarding livestock welfare and productivity.

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