One of the consequences of climate change seems to be increasingly volatile weather systems accompanied by rapidly changing and frequently unseasonal temperatures.
As November gave way to December at the end of 2015, for example, parts of the UK experienced short, sharp cold snaps, followed by returns to the mild, not to mention wet, conditions.
Managing layer flocks requires finely tuned decisions at the best of times, and the winter months can set new challenges for the unwary.
See also: Optimising air flow for layers
In the temperate regions of Europe, normal cold winter days and nights rarely present a threat to the survival of adult birds. However, cold weather still brings with it a whole set of complications that require careful management in both colony and free-range systems.
Drafts, humidity fluctuations and the temptation to restrict ventilation in pursuit of keeping birds warm all create challenges.
Heating and ventilation
To avoid problems associated with humidity, heating and ventilation need to be carefully balanced. Laying house temperatures should be kept between 18C and 22C. At lower temperatures hens will increase feed intake as they use energy to maintain body heat.
To avoid temperature stress in winter, it is advisable to preheat the production houses up to 18C before transferring point-of-lay pullets, and to respect minimum ventilation requirements to avoid damage caused by high carbon dioxide and NH3 levels.
It is, however, preferable to go down in temperature than to go up in carbon dioxide/NH3 levels.
An important priority is the provision of fresh air. If the air inside the poultry house is stuffy, humid, smelly or laden with dust, then the rate of air change is too low.
Besides supplying the poultry house with fresh air, these points must be taken into consideration:
- Removal of excess moisture helps to maintain a good litter quality and healthy birds
- Removal of dust from the atmosphere helps to prevent disease, as disease organisms tend to associate with dust particles
A free-range house may be ventilated mechanically, naturally, or by a combination of both systems.
Fundamental to any system is the need for finely adjustable air inlets, usually at eaves level on both sides of the house, and outlets in the apex of the roof – the ridge. However, some houses may be cross-ventilated, with inlets one side of the building and the extractor fans on the other side.
When rate of air change is low, it is important that air is circulated, so that fresh air reaches all parts of the house.
If the warm air, from higher levels in the building, is mixed with lower level air, birds will enjoy a more balanced temperature.
Mixing air also allows greater removal of moisture from the litter, keeping it dry, though it is important to avoid direct draughts on the birds.
Though well-equipped to survive winters in the UK, layers can prove almost as sensitive to our instincts to help them keep warm as they can to a brief cold spell. As such, the advice is to be observant, understand what the behaviour is telling you and try to maintain the conditions the birds are accustomed to.
Nests have to be comfortable, to encourage birds to lay there. During winter, prevention of direct cold draughts around the nest is vital. The purpose of heating and ventilation is to create a comfortable area close to the nest – more comfortable than the other parts of the laying house.
Although unpredictable, smothering is more frequently observed in houses with inadequate ventilation, uneven in-house temperature and/or draughts. These must be avoided.
When the temperature drops, feed intake will be increased as the birds use more energy to maintain their body heat. But as feed intake is highly correlated with egg size, you may see an increase in egg size, too.
A proper water supply is one of the key factors to maintain flock health. Producers must be extra vigilant at times of low temperatures, to make sure that pipes don’t freeze.
When cold air enters the house, it falls rapidly to the floor, displacing the warm air. This cold air is not able to absorb humidity as well as warmer air, and this can lead to litter becoming caked, producing higher amounts of ammonia and carbon dioxide. This may cause inflammation of the respiratory tract and further respiratory problems.