Question of the Week
Answer: Heat stress in poultry can be very serious, with layers being particularly susceptible. Birds will reduce their feed intake a great deal, since most of the energy in their feed is converted to body heat and reducing intake helps reduce heat stress. This reduction in feed intake means that egg production declines rapidly and may stop altogether.
Use of fans and misters in the poultry house is important in cooling the birds. However, misters should not be used to the point where humidity in the house is too high. Litter is also a source of moisture and needs to be managed so that humidity in the house is no more than 70% (1). Reducing stocking density can also help reduce the number of birds producing heat.
Fortification of water with vitamins and electrolytes is wise, especially when feed intakes are low due to hot weather. You can buy products like Merrick's Blue Ribbon Poultry Electrolyte Pack for this purpose.
Increasing nutrient intake during heat stress, by changing the feed specification, may have an adverse affect on survivability, but increasing the digestibility of nutrients and the use of specialist micro ingredients has been shown to have benefits.
The principal nutrients to consider are (1):
• Proteins and amino acids: nutrient digestibility should be increased rather than nutrient density, minimize excess protein and balance amino acids and minimize the crude protein level in the diet.
• Energy: the diet should be supplemented with fat rather than carbohydrate. Increasing the energy density of the diet will increase growth rate but will also increase heat output.
• Vitamins and minerals: certain vitamins are known to have a positive effect on the birds’ response to heat stress including Vitamin E, D, A, C, B2 and nicotinic acid. Under no circumstances should vitamins be withdrawn from the diet. A product such as Fertrells Nutri-Balance premix for feed may be useful for this.
As temperatures rise, the bird has to maintain the balance between heat production and heat loss, and so will reduce its feed intake. Reduced feed intake is the main cause of poor performance at high temperatures and the feeding practices below have been shown to have a positive effect on survivability and performance of birds experiencing heat stress (1):
• Ensure good physical quality of feed (crumb, pellets or mash) to encourage appetite. If floor space allows add extra feeders.
• Feed should not be stored for longer than one week to reduce the possibility of mycotoxin build up.
• Encourage eating at cooler times of the day as it takes 2-4 hours after feeding before the maximum energy is generated and the bird must dissipate the metabolic heat generated.
• 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—low light intensity during periodic feeding reduces activity which reduces heat load.
• Reduced feed intake can increase susceptibility to calcium tetany. To ensure adequate calcium is available for eggshell production, feed oyster shell grit as a scratch feed. Feeding 1.5g of oyster shell grit per bird (.05 ounce, or about a third of a teaspoon) will replace this.
1) Cockshott, Ian. No date. Hot weather broiler and breeder management: Ian Cockshott, Technical Service Manager for Ross in the Middle East & Africa looks at practical ways to manage stock in hot weather. Aviagen Technical Note. www.aviagen.com
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