Poultry can only regulate their body temperature within a narrow range of environmental temperatures (between 16 and 26°C). In the tropics, environmental temperatures are usually above this zone during most of the year, write S.S. Diarra and P. Tabuaciri of the University of the South Pacific in Samoa in the International Journal of Poultry Science.

High ambient temperatures adversely affect the performance of poultry, with meat-type birds being more susceptible than egg-type birds, the authors found in their review of published literature on the subject.

The authors' key finding is that the poor performance of poultry under high ambient temperatures is mainly as a result of decreased feed intake, which consequently reduces growth and meat quality, egg production and egg quality and efficiency of feed utilisation.

Several feeding practices have been used to alleviate the adverse effects of high temperatures on poultry performance.

Although most studies on nutritional management of heat stress have been carried out in broilers, there are also few reports on nutritional management in laying hens under conditions of heat stress.

In their review, the authors found that feeding pellets rather than mash or wet feeding may help to maintain feed intake. Changing the nutrient content of the diet also appears to help if the energy level is reduced and the protein increased under conditions of moderate heat stress. Choice feeding has also been shown to be effective as the birds select the nutrients they need at particular times of the day.

Supplementation of the diet or drinking water with electrolytes may be helpful but this needs to be done with caution or it may be counter-productive and lead to problems with wet litter.

The beneficial effects of vitamins on the performance of poultry under heat stress are well documented for vitamins A, D, E and B complexes, while the results with vitamin C have been variable.

Withdrawal of feed during the hottest times of day and feeding during the early morning and evening have been successful, and there may be further benefits of increasing feeder space, or providing additional feeders during periods of high temperatures.

Finally, it is important to supply plenty of water to poultry during periods of heat stress. They drink more as the temperature rises, and water temperature and drinker (type, height and shape) have all been found to affect bird performance.

Feeding management practices such as alteration of energy: protein ratio, wet feeding, electrolyte supplementation, feeding time, drinker type and height have been found to improve performance under heat-stress, concluded Diarra and Tabuaciri.

They added that the effectiveness of these practices may vary for a number of reasons, including the duration and intensity of heat, relative humidity, air velocity, class and age of birds.

Reference

Diarra S.S. and P. Tabuaciri. 2014. Feeding management of poultry in high environmental temperatures. International Journal of Poultry Science. 13:657-661.

March 2015