Novel heat stress interventions to cool off birds
BY ALAIN RIGGI, GLOBAL SPECIES MANAGER POULTRY, PHILEO BY LESAFFRE W
hen the chicken is healthy and performing at its best, the bird is in a state of physiological equilibrium (homeostasis). When the animal is exposed to stressors, coming from external
sources (such as heat stress) or internal sources (such as meta- bolic disorders), the homeostasis is disrupted. Poultry seems to be specifically sensitive to temperature-associated challenges, especially heat stress. If the body temperature rises more than 4°C, the bird will die. Preventing poultry from heat stress helps maintain the homeostasis of the animal, which has a direct positive effect on bird and egg performance, animal health and welfare and farm profitability.
Recognise the ‘heat’ alarm bells It is key to know when the heat alarm bells go off and when to take action. Simply looking at the ambient temperature is not enough. Also humidity plays a role. The THI (Temperature Hu- midity Index) measures the combined effects of ambient tem- perature and relative humidity to define the level of heat stress. At a THI of >30, we speak of severe heat stress. Chickens in the thermal stress condition spend less time walking and standing, consume less feed and more water, spread wings, and cover
Heat stress impact on poultry production and profitability
A number of studies showed that heat stress not only causes suffering and a re- duction in performance, it can also lead to death and substantial economic losses:
50% feed intake 25% feed efficiency 30% body weight 30% egg production
16
30% calcium uptake 20% shell thickness 4 points in survival rate 2 billion USD per year globally
▶ HEAT STRESS | MAY 2021
In most regions, summer is around the corner and poultry farmers need to prepare the birds to combat the heat and hence stay productive. Adding a powerful yeast postbiotic can help broilers absorb nutrients more readily and keep cool.
their body surface in the litter. At first sight you might only see that the behaviour of the birds change, but heat stress has an effect on a range of physiological processes that are not visible straight away, such as an elevated corticosterone levels in the blood, a weakened immune system, changes in reproductive hormones, eggshell mineralisation and loss of gut integrity (leaky gut). All these physiological adjustments ultimately lead to a reduced zootechnical performance.
Proper housing and adjusted feeding Different actions should be taken to manage the heat stress. Poultry houses should include correct orientation to allow air flow, spacing between houses, increased ventilation capacity, fogging and evaporation systems to provide the best possible production conditions. In addition to poultry house manage- ment, the main changes that producers can implement at farm level are feeding strategies and nutritional management. Feed- ing strategies for broilers may include to withdraw feed 3-6 hours before the heat stress peak and reintroduce feed 6 hours after the peak. Another strategy that has been proposed to en- hance broiler productivity during heat stress is to impose a feed restriction at an early age (4 to 6 days old) to adapt the diges- tive system to fasting during acute heat stress periods later in life. Nutritionists can also adapt the fat and protein contents of the diets. Studies showed for example that increased fat levels in the diet of heat-stressed broilers keeps feed intake levels up and allows them to better cope with high temperatures. Utilis- ing wet feed during heat stress periods is another feeding measure and helps increase dry matter intake in layers and broilers. And of course, cool and fresh drinking water should be available at all times, because water works as a coolant.
The power of yeast postbiotic Next to the important housing and feeding strategies, the application of dietary solutions that improve gut integrity and health are of fundamental interest to combat the negative effects of heat stress and to keep bird performance, health, welfare and farm profitability at the desired levels. Yeast postbiotics, rich in mannan-oligosaccharide (MOS) and ß-glucans, have been shown to modulate immunity, preserve
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