Holistic Nutritional Management approach for mitigating Heat Stress

Dr. Pothanna J, Technical Manager, Trouw Nutrition South Asia 

In India's major poultry-producing areas, the scorching temperatures during the months of April to June pose significant challenges. Heat stress during this period leads to increased mortality rates, reduced egg production, and slower growth in young pullets. To mitigate these effects, an effective heat stress management system is imperative. 

Heat stress in poultry arises from a combination of factors. Primarily, the absence of sweat glands leaves birds reliant on alternative cooling mechanisms. Environmental conditions play a significant role, with high temperatures, humidity, and inadequate ventilation exacerbating the heat stress. Additionally, suboptimal management practices such as irregular feeding schedules and poor litter conditions further compound the issue. 

Normal Body Temperature	41.2 °C to 42.2 °C  106 °F to 107 °F
Ideal Temperature Range	65 °F to 75°F  18.3 0C to 23.90C
Thermoneutral Zone	55°F to 75°F

 

Heat stress Index (HSI) - The Heat Stress Index (HSI) in poultry is the sum of ambient temperature (°F) and relative humidity (%), indicating the combined impact of these factors on bird welfare.  

Thumb rule - When the HSI surpasses 160, it is more probable that heat stress will occur, leading to adverse effects on flock performance. Comfort zone (<140 HSI). 

In the thermoneutral zone, birds lose heat using clear methods such as radiation, convection, and conduction. They also lose unconscious heat through evaporation, which is especially noticeable during summer. High temperatures cause the hypothalamus to activate the adrenocortical axis, which increases corticosteroid release. This increases physiological load in birds and worsens heat stress. Long-term exposure to high temperatures and humidity causes panting, which may be insufficient to regulate body temperature, and the birds suffer from heat stress. 

Panting allows the bird to control its body temperature by draining water from its respiratory surfaces and air-sacs. Long-term exposure to high temperatures and humidity produces panting, which may not be sufficient to regulate body temperature, and the birds experience heat stress. Hot, humid weather is more demanding than hot, dry weather. Panting causes heat loss as moisture evaporates from the airways, a tenfold increase in respiratory rate, and an alteration in the blood's acid-base balance, leading in respiratory alkalosis. Carbon dioxide (CO2) loss raises plasma pH and mineral deficiency, such as potassium (K) leads to decreased growth rate, excessive humidity, and warmth limit evaporative heat loss and, in severe cases, cause death. 

Mitigation strategies:  

• Water Management  
• Feed management.  
• Health Management  
• General Management  

 

Feed Management  

Birds require more energy to cool down in hot weather, so their energy needs increase. Surprisingly, when temperatures rise over 21°C, animals require slightly less energy for fundamental processes. However, it is still a good idea to increase their energy intake by 10% to assist them cope with the heat. Adding a small amount of fat or oil to their diet, up to 5%, can also be beneficial because lipids give a lot of energy and release less heat during digestion. They also slow down the digestive process, allowing animals to absorb more nutrients. Some fats like soybean, canola, walnut, flaxseed, and fish oils, include omega-3 and omega-6 fatty acids, known as polyunsaturated fatty acids (PUFAs), which are beneficial to health. 

Hot weather affects animal protein metabolism, leading to decreased synthesis and increased breakdown. To prevent coccidian growth, it's crucial to balance diets with specific amino acids and protein-rich ingredients. This balance prevents excessive liver fat accumulation and improves heat stress coping. Heat stress also reduces arginine absorption, leading to protein breakdown. To counteract this, feed formulations should focus on vegetable proteins like soy, sesame, and sunflower. 

Poultry farmers face challenges during summer due to increased feed intake. To ensure birds' health and survival, they restrict feeding before peak temperatures. Broilers receive a protein-rich diet during cooler times and an energy-rich diet during warmer periods. Laying birds receive once-a-day feeding in the evening to maintain calcium reserves and eggshell quality. Pelletized feed reduces energy expenditure, improving efficiency. High-quality pellets are crucial for optimal feed conversion. Wet mash feeding is recommended in regions with high temperatures and humidity for better bird performance. 

Feeding birds at the right time of day is crucial to help them cope with heat stress. Late afternoon can cause significant body temperature rise, potentially leading to bird mortality. To avoid unnecessary heat load, feed should be withdrawn 8 hours before peak temperature. One-third of the daily feed ration should be given in the morning and two-thirds in late afternoon. Calcium is available during night formation, improving shell quality and preventing depletion of bone calcium. Midnight snacks can provide extra feeding time in cooler parts of the night. Feed stimulation can help raise feed consumption and stimulate intake. Practices include wet mash feeding, pellet or crumble feed, low-calcium diets, frequent feeding and stirring, adding fat or molasses, running feeder chains more frequently, emptying feeders, and running feeders empty at least once a day. To ensure optimal nutrient intake in summer, increase the nutrient density of the ration by adding nutrients, vitamins, and minerals to compensate for reduced intake. 

Top of Form 

During summer heat stress, poultry may experience increased excretion of minerals, leading to lower levels of essential nutrients in their bloodstream and liver. Antioxidant minerals such as chromium are crucial for aiding glucose clearance through insulin receptors, promoting glucose uptake into cells. Zinc, found in various proteins and enzymes, plays a vital role in immune function, cellular growth, and defence against free radicals. Selenium, when present in higher concentrations, has been shown to enhance antibody levels, counteracting the negative effects of heat stress. Summer heat can also reduce calcium intake and the conversion of vitamin D3 to its active form. However, excessive dietary calcium can decrease feed intake and palatability. Therefore, it's recommended to provide calcium separately, such as through oyster shell grit or limestone chips, during the afternoon. Additionally, excessive phosphorus can inhibit the release of bone calcium and the formation of calcium carbonate in the shell gland, compromising shell quality. Proper management of these minerals is crucial for maintaining poultry health and productivity during summer heat stress. 

 

Feed Additives – 

Vitamin C: Vitamin C, also known as ascorbic acid, is crucial for poultry nutrition, especially during heat stress. Its antioxidant properties combat oxidative stress and protect cells and tissues from damage, promoting overall health and resilience in poultry. Its primary role is in scavenging free radicals. 

 Vitamin C is crucial for collagen synthesis, a structural protein essential for connective tissue, bone, and blood vessel integrity. It supports tissue repair and maintenance during heat stress, aiding in the recovery of damaged tissues in poultry. Vitamin C enhances the immune response in poultry by supporting the activity of immune cells and cytokines, thereby strengthening the immune system's ability to combat infections and diseases, particularly during environmental stress. 

Vitamin C serves as a cofactor in the conversion of inactive vitamin D to its active form in poultry. This process occurs primarily in the liver and kidneys, where 25-hydroxyvitamin D is formed, the major circulating form. This vitamin D is then further hydroxylated in the kidneys by enzyme 1-alpha-hydroxylase, resulting in the biologically active form 1,25-dihydroxyvitamin D. This active form regulates calcium and phosphorus metabolism, bone health, and immune function in poultry. Vitamin C's role in this enzymatic reaction enhances vitamin D's biological activity. 

 

Betaine

Betaine is a versatile compound with several critical roles in biology, functioning as both a methyl donor and an osmo-regulator. Originally discovered in sugar beet juice, betaine is derived from the amino acid glycine and has a neutral, bipolar structure known as a zwitterion. This unique structure as shown in Fig.1 allows it to participate in various biological processes while protecting cells from environmental stress. 

Figure 1: Chemical structure of Betaine 

 

Chromium

Chromium is a vital mineral in poultry feed, particularly during the summer, when heat stress can impact bird health and metabolism. Its primary role involves supporting glucose metabolism by enhancing insulin sensitivity. Chromium interacts with chromodulin, a peptide that strengthens the bond between insulin and its receptor, facilitating improved glucose uptake into cells. This improved insulin function helps maintain stable blood glucose levels, ensuring efficient energy use, which is crucial when heat stress elevates energy demands. By reducing metabolic stress through efficient glucose clearance, chromium can help mitigate the adverse effects of heat stress. 

Additionally, chromium contributes to improved immunity and reduced cortisol levels, further aiding poultry health during summer. By enhancing insulin sensitivity, chromium indirectly supports stronger immune responses, offering birds better protection against diseases exacerbated by heat stress. Moreover, by stabilizing glucose levels, chromium helps lower cortisol, a stress-related hormone that can hinder growth and immune function. The combination of these effects allows poultry to maintain better health and productivity during high temperatures, making chromium a valuable addition to summer feed formulations. 

Conclusion

Farmers can adopt a comprehensive approach to mitigate summer heat stress in chickens by combining environmental controls, feed and water management, and stress-reducing treatments. Trouw Nutrition's Maxcare AHS (Anti-Heat Stress) is an important product to consider because it contains Betain, Vitamin C, and Chromium, which are known for their anti-stress and antioxidant effects. These substances assist broilers and layers stay healthy and perform well in high temperatures. The Maxcare AHS dosing rate ranges from 0.5 kg to 1 kilogramme per tonne of feed. Implementing such solutions, combined with typical management approaches, can considerably lessen the impact of heat stress, leading to lower death rates, improved egg production, and faster growth rates in young pullets. 

 

For further information, kindly write to us at customercareindia@trouwnutrition.com or visit our website: www.trouwnutrition.in