FEEDING STRATEGIES IN POULTRY IN HOT CLIMATE

FEEDING STRATEGIES IN POULTRY IN HOT CLIMATE

Hot weather is a common problem in tropical countries with summer temperatures  above 30 ºC.  The detrimental effects of a hot environment on the performance of  poultry have been well documented.  As temperature rises, the bird has to reduce its feed consumption to reduce heat from metabolism.  Research demonstrated  that feed consumption is reduced by 5% for every 1 ºC rise in temperature between 32—38 ºC.  

Hot regions significant losses every year because of heat stress, which resulted in economic losses to the poultry farmers.  In poultry production, heat stress can be described as acute or chronic.  Acute heat stress refers to short and sudden periods of extremely high temperature, whereas chronic heat stress refers to extended periods of elevated temperature.  In broilers, growth rates, feed efficiency and carcass quality are negatively affected.emperature increase the broilers’ time to reach market weight and increase mortality.  In laying hens, heat stress leads to a decline in egg production and egg quality, as well as, shelf life of eggs is shortened.  High ambient temperature coupled with high humidity decreases  fertility resulting in low hatchability.

During heat stress feed intake is depressed while water intake is increased.  The decline in feed intake leads to poor bird performance.  To alleviate the effects of heat stress, dietary manipulations are necessary, as these can help reduce metabolic heat production and maintain nutrient intake.  It is also necessary to minimize bird activity during the hottest parts of the day in order to lessen the heat burden.

A.    Some Responses Of Birds To Heat Stress

When exposed to high temperatures above comfort zone, domestic fowls may splash water on their combs and wattles in order to increase evaporative cooling  from these surfaces.  Heat stressed birds also spend relatively less time engaging  in social behaviour and in changing posture.  Also,  the wings droop and are held slightly away from the body to enhance cooling.  In a natural environment, birds will look for a shady and cool area.

Birds are heat stressed if they have difficulty in achieving a balance between heat production and body heat loss.  At thermoneutral or comfort zone, birds can lose heat at a controlled rate, whereas above critical temperature they lose heat actively  by panting.  If heat production exceeds maximum heat loss either in intensity or over long periods of time, birds may die.  Temperature increase by 4 ^oC above 41^oC will give rise to death in broilers.

B.     Feeding Strategies

During hot weather birds reduce feed consumption resulting in some nutrients becoming deficient.  To encourage feed consumption during heat stress various feeding strategies are employed in many tropical and subtropical environments which are outlined below.

1.      Increase nutrient density of the diet

The energy content of the diet be increased during hot weather.  The use of supplemental fat is suggested.  Dietary fat increases palatability of feeds and reduces the amount of heat increment that is produced during its utilization in the body.

2.      Increase dietary protein

To ensure that layers do not suffer nutritional stress of hot weather, it is recommended that protein content of feed should be increased from 16% to 17—18%.  It is contended that increasing dietary protein content would cover the  requirements for isoleucine and typtophan, while methionine and lysine can be supplemented with synthetic compounds provided that they are cheaper than natural sources.  Fear that increasing dietary protein might be detrimental to the  bird as more heat is produced during its utilization that may well overload heat dissipation mechanisms.  Improving overall balance of the diet by amino acid supplementation appears to be more effective than increasing protein intake.

3.      Feeding calcium carbonate or oyster shells

Calcium content of the diet should be adjusted according to anticipated level of intake, such that each bird consumes the right amount per day.  For laying hens,  top dressing feed with oyster shell or large particulate limestone is beneficial and  has the added advantage of stimulating feed consumption.  Limestone and oyster chips may be provided at a rate of 625 g per 100 hens.

4.      Feeding management

The feeding practices suggested below are reported to improve performance of birds under heat stress.

·         Ensure good physical quality of feed (crumb, pellets or mash) to  encourage appetite.

·         Feed should not be stored for longer than two months, especially in summer to reduce the possibility of mycotoxin build up.

·         Encourage eating at cooler times of the day, i.e., early morning or in the evening.  Feeding birds at cool times enables birds to make up for what they have not eaten during the day. 

·         Remove feed 4 to 6 hours prior to an anticipated heat stress period.  Birds should not be fed or disturbed during the hottest part of the day.

·         Dim the lights while feeding–using low light intensity during periodic feeding reduces activity that reduces heat load.

5.      Supplements (minerals and vitamins)

Imbalances in acid-base balance occur in heat stressed birds.  Therefore,  inclusion of various compounds in the diet or water is a common practice to  alleviate the adverse effects of heat stress.  These include sodium bicarbonate (NaHCO₃), potassium chloride (KCl), calcium chloride (CaCl₂), ammonium chloride (NH₄Cl) and vitamin C (ascorbic acid).  Sodium zeolite and aspirin are also beneficial in reducing the effects of heat stress in laying hens.  Phenix stresspac via drinking water to alleviate effects of heat stress on poultry.  Ascorbic acid and NaHCo₃ appear to be the most popular electrolytes used in tropical and subtropical poultry production. 

During heat  stress the chicken is not able to synthesize enough vitamin  C to  meet physiological demands, hence the need for mineral and vitamin  supplementation.  Chickens require vitamin C for amino acid and mineral  metabolism as well as for synthesis of hormones.  Supplementation of vitamin C in drinking water at 40 milligrams per bird per day is reported to give beneficial effects in broilers.  In laying hens, 20 milligrams per litre of water is recommended.  Also, aspirin in soluble liquid form can be used for its antipyretic (cooling) effect at the rate of 0.3 grams per litre of water.

Sodium bicarbonate at high temperature stimulates water and feed consumption as well as contributing to improved weight gain.  The addition of 8 grams of sodium bicarbonate to the100 litres of drinking water (or 35 grams per 25 kilograms) can be useful in heat stressed  broilers to stimulate water consumption.  For  broiler breeders, 0.05 to 0.30% are reported to give beneficial results.