Nutritional management of heat stress in broilers

Sandeep Uniyal, Amit Sharma and Udeybir Singh Chahal

Department of Animal Nutrition Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana-141001

Introduction

Indian poultry sector have grown enormously in past few decade from traditional backward to modern highly intensified poultr y production system. The Indian poultry sector now has grown to 120,000 Cr industry which in itself largest among the agriculture sector and contributing nearly 5 % in the GDP from agriculture sector. India is second and third largest producer of egg and poultry meat respectively, which is a good sign to Indian poultry industry but there are certain factors which are obstacle in expression of full potential of Indian poultry industry one of them is environmental stress particularly heat stress. The environmental temperature start increasing from March till the start of monsoon in most of the part of India and may reaches above 500C in certain parts. So, it becomes very difficult for the poultry birds to cope up with these hot weather conditions which adversely affects the feed intake and performance of birds in terms of weight gain and feed conversion ratio. It also leads to reduced nutrient utilization and immune suppression in the broilers birds so, it is at most important to take necessary measures to prevent heat stress in broiler birds. Nutritional management of heat stress involves various approaches like form of feed and feeding method, time of feeding, energy and protein level of the feed, electrolyte balance, vitamins and minerals level in feed and water and dietary feed additives

1. Forms of feed and feeding

method: Feed forms (crumb, pellets, or mash) plays important role in minimizing heat stress in the birds. It has been observed that feeding broiler pelleted feed with minimum amount of fines reduces heat stress in birds by minimizing the proportion of energy wasted in acquiring the feed and also save the time (1/3rd) in feeding as compared to mesh. Pelleted feed also improve fed intake (upto 14 %) and digestibility in heated stressed birds. Reduced fine by 10 % of feed in summer gives better performance by improving FCR by 0.01, since energy spent for feeding is less. 2. Time of feeding: Timing of the feeding plays important role in alleviating heat stress in broiler.

Production of heat by the broiler can be reduced by feeding them during cooler hours of the day i.e early in the morning and late in the evening this will reduce heat

stress induced mortality by minimizing heat increment due to feeding during hotter part of the day. 3. Energy density of the diet: The energy level of the diet should be increased to cope up the reduced body weight as a consequence of lower feed intake in the birds under heat stressed condition this can be done by adding fat in the diet which increases energy density of diet and also reduces heat production in the birds as fat has lower heat increment then protein and carbohydrates. It has been reported that feeding high fat diets (5%) helped in reducing the detrimental effect of heat stress in broilers raised at 2936°C.

4. Level of protein and amino

acids in diet: level of protein in the diet of broiler during heat stress should be monitored to combat adverse effect so, a nutritional balanced diet with low level of protein with additional supplementation of limiting amino acids minimizes the energy loss from excreting surplus nitrogen and might therefore help the chicken to cope with heat stress. High protein diet during heat stress decrease growth rate and meat

yield because of protein has high heat increment.

5. Dietary electrolyte balance:

Dietary electrolyte balance is essential to prevent heat stress in the birds and for better feed intake, body weight gain and feed conversion ratio (FCR).

Electrolytes like sodium (Na),

Potassium (K) and chloride (Cl) is essential for synthesis of tissue proteins, maintenance of intracellular and extracellular homeostasis, electrical potential cell membranes, enzymes reactions, osmotic pressure and acid-base balance. Drinking water supplemented with sodium or potassium salts causes increased water consumption in broilers by 85% and resulting in greater weight gains. At high temperature of 35˚C, addition of 0.5% KCl and 0.39% NaCl in drinking water reduced the severity of heat stress in broiler.

Also addition of ammonium chloride, potassium chloride and sodium bicarbonate have improved performance of chicken by improving water and feed intake. Generally dietary electrolyte balance should be increased by 10 to 15% in summer than winter.

6. Vitamins and minerals level:

V i t a m i n s a n d m i n e r a l s s u p p l e m e n t a t i o n p l a y s important role in prevention of heat stress in the birds and helps in maintaining production performance. As results of decrease in feed intake during summer intake essential micronutrients like Vitamin A, C, E, zinc, selenium, chromium etc availability also reduced and these micronutrient are well known for their anti stress effects

So, supplementation of these v i t a m i n s i s h e l p f u l f o r maintenance of performance and immune function. It has been reported that supplementation of Vitamin A, Vitamin E and

Vitamin C @ 8000 IU/kg, 250 mg/kg and 250 mg/kg diet respectively, alleviates the heat stress condition in broiler and i m p ro v e s p e r f o r m a n c e .

Supplementation of chromium picolinate along with vitamin C has shown synergistic effect in combating heat stress. Also it is recommended in summer to increase the trace minerals level by 10-15 % in the diet of broiler in summer. 7. Dietary Feed Additives: Heat stress can induce unfavourable changes in indigenous bacterial microbiota which lead to impairment in digestibility lower productivity of the birds.

Supplementation of multi strain probiotics may enrich diversity of micro flora in chicken. Restore microbial balance in jejunum and

caeca of chicken may help in reduce harmful effects of heat stress. Phytochemicals like polyphenols, essential oils, and flavonoids helps in restoring feed intake, body weight and FCR in heat stressed birds. Similarly addition of betaine that acts as a methyl donor and maintain osmotic balance of body will be useful as an on-top application during intense summer stress. It has been reported that during heat stress heights of the villi in the instenstine of birds decrease which leads to less absorptive surface area and thus reduced nutrient absorption. So, supplementation of Butyric acid or Na butyrate helps in stimulating villi growth and serves as primary energy source for intestinal epithelium.

Conclusion

Nutritional management through above dietary approach certainly help in reducing heat stress in broilers and improving productivity performance by increasing feed intake, body weight gain and better feed conversion efficiency there by improves farm profitability in summer season. r