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Nutritional interventions in alleviating the effects of high temperatures in broiler production
Published online by Cambridge University Press: 18 September 2007
Abstract
Commercial broilers are increasingly being subjected to environmental temperatures that are above their comfort zone. This is mainly because birds are growing faster than before and are therefore larger at any given age, but also because broiler production is being introduced as a farming system in environments that are unsuitable for such production. It is not economic for most producers to modify the environment within the broiler house to account for these problems and so it would be useful to know of nutritional strategies that could be used to reduce the effects of heat on broilers in the finishing stage.
Nutritional strategies discussed in this paper include the use of feeds with a high ratio of net energy to metabolisable energy, feeds whose amino acid composition is closer to that required by the birds, feeds with additional salts or vitamins and the use of pelleted feed and timed feeding. However, dietary modification will increase the cost of feed and the producer will usually not reap a net benefit. Some advantage may be gained by adding vitamins C or E to the feed, because of their action in reducing lipid peroxidation resulting from the increased body temperature of the bird: but it is impractical to reduce the heat increment of a broiler feed unless poor quality ingredients are currently being used. Heat production by the broiler may be lowered by reducing activity, by feeding pellets instead of mash, or by withholding access to feed before the temperature increases to stressful levels. Some improvement in performance can be obtained by increasing water intake. This can be achieved by cooling the drinking water and by adding salts, though these are only effective if the water is kept cool.
Most nutritional strategies that have been proposed as a means of reducing the heat of digestion in the broiler result in a maximum theoretical saving in metabolic heat production equal to the effect of lowering dry bulb temperature in the broiler house by about 1°C. None of these strategies is as effective in terms of growth rate, feed conversion, liveability or carcass quality as reducing the radiant heat load on the birds by making appropriate modifications to the structure of the broiler house and to the husbandry practices employed.
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