Coping with hot weather
While sun worshippers may welcome the arrival of summer sunshine and high temperatures, these weather conditions can cause problems for free range flocks.
The most suitable temperature for laying hens is around 17-18ºC. At this temperature, the bird uses very little energy on maintaining her body temperature either to keep warm or to lose heat.
If the environmental temperature drops below or above this temperature, then the birds need to use energy to cope and the energy used must be got rid of as heat. Losing the extra heat produced becomes a problem to the bird when the environmental temperature is very high.
The birds’ initial response to increasing temperature will be to breathe with the beak open (panting) to lose heat through evaporation or to stand with the wings stretched out and feathers fluffed to increase heat loss by radiation and convection. In hot conditions birds will want to spread out and have some space around them. Birds will also increase water intake.
At very high temperatures, birds will reduce energy usage by reducing feed intake and stopping egg production.
If environmental temperature becomes too high, the bird becomes unable to lose enough heat and can no longer control body temperature. Once this happens, the birds become prostrate and will die as the bird overheats and body systems are unable to function.
The design of modern free range houses with high roofs, good insulation and good air movement and relatively low stocking density mean that it would be unusual to see high mortality primarily due to high temperatures in free range flocks. The main problems experienced are of adverse effects on production with a drop in the number of eggs produced but also effects on egg size and shell quality as a result of depressed feed intake and the birds’ need to conserve energy.
The effects of high temperature will be greatly aggravated if relative humidity is also high as it is then more difficult for birds to lose heat.
Bright sunlight over a prolonged period can also affect shell colour, with an increase in pale shells – this frustrating problem has been the subject of previous articles and a study is now underway to try and understand why flocks are affected in this way.
In addition to the direct problems caused to the hen herself by high temperatures, high environmental temperatures also favour the growth of various infectious agents including bacteria, viruses and parasites.
Of most concern is the issue of red mite. As most producers will know, red mite is a significant problem in many free range units. In hot weather, the mite life cycle is speeded up and numbers can escalate alarmingly in a very short period of time. In severe cases, this can lead to mortality due to anaemia in affected flocks and can have significant effects on production.
Some viruses and bacteria also thrive in high environmental temperatures. This is of particular relevance to water systems in free range units where total bacterial counts in water can rise very quickly. Water with a very high level of bacteria present may be unpalatable for the birds and reduce water consumption but can also act as a source of infection particularly with E coli and Pseudomonas.
So what can be done to reduce the risks of heat stress and damaging effects on production in hot weather?
1) Environment. House design to maintain a stable environment for the bird is essential. Of particular importance is maintaining a good air flow through the house to help keep birds cool.
2) Encouraging birds to range. Hens do not like to go out in bright sunlight and may tend to stay in the house during the hottest part of the day which may compound the heat stress problem. If areas of shade are provided on the range, for example by planting trees, this will encourage birds to leave the house and will, in itself, help to reduce house temperature. If it is not possible to plant trees then artificial shelters should be provided.
3) Maintain a plentiful supply of cool, clean water. If there is a water tank in the shed, this should be sited in a cool place if possible. In high environmental temperatures, water sanitisation may be of help in reducing bacterial load.
4) The use of electrolytes and vitamins via drinking water may also help birds to cope with the heat. It may be worth using drinkers eg ‘Quill’ type on the range to maintain water intake.
5) It may be necessary to look at altering the timing of feed so that birds are fed at cooler times of the day to try and maintain feed intake.
6) Plan ahead! Long range weather forecasts are available (although not always correct!). This enables producers to plan ahead if hot weather is predicted.
Summer weather is not all bad news! Sunlight is a good natural disinfectant and will help to reduce parasites such as worms on pasture by desiccating worm eggs and also kill some viruses and bacteria.
