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By Ian Dowsland, Regional Account Manager - UK, Aviagen
As winter approaches, the change in season brings unpredictable weather and the prospect of more difficult growing conditions. The cooler weather means that the main ventilation objective in the poultry house changes from one of cooling, to one of heat conservation. Trying to limit the volume of air entering the house, can affect air quality, uniform temperature distribution and litter quality, all key factors in ensuring good bird health and performance. As a result any problems which have been seen during the summer months will generally be compounded in the winter.
A large-scale field experiment investigating the relationship between stocking density and environmental conditions on bird welfare has been recently reported (Dawkins 2004). The experiment showed that when house temperatures and humidity did not match the stated target profile, the birds performed less well, and their welfare status was relatively poor. These findings stress the importance of good environmental control throughout the year particularly in winter when targets are more difficult to achieve
Chick intake
Aviagen emphasises the importance of maximising first week performance. If chicks do well in the first week and are not compromised during the growing period, they finish well. A good start ensures the early development of the gut and immune system and means that you are much less likely to see enteric and other health issues during the life of the flock. In addition, drivers and farm managers must be made aware of the threat to performance by leaving the chicks in the cold for any length of time.
It is important that the house is properly pre-heated before the chicks arrive. Floor temperature is a good indicator of this, see Table 1.
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Table 1: Effect of floor temperature on chick performance
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Floor
Temperature (°C)
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25
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30
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Seven
Day Weight (g)
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151
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165
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Daily
Gain (g)
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51.5
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53
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FCR
to 1.5kg
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1.48
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1.45
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A broiler's lifespan is typically under 1000 hours with 1 day of life equating to 2% of its lifespan. It follows that if any problems arise they must be dealt with promptly. The first sign of any potential problem will be a change in behaviour and close observation of the birds can help with early detection allowing remedial action to be taken.
Unwell birds are often "flat" quiet and slow to respond to human activity. A good indicator is the position of the tail. If it is erect, birds are likely to be healthy, but when it is horizontal or inverted this can indicate that all is not as it should be. If you see any signs of illness, contact your local vet.
Monitoring daily feed and water consumption can also aid early detection of possible health problems. A reduction, levelling or spike in consumption can all indicate that there may be an issue. In the case of enteric problems, consumption tends to level out for around 3 days, followed by a sharp increase. Feed and water consumption can also be influenced by changes to diet or in feed form (pellet quality).
Heating systems
Regular maintenance of the heating system is paramount as it can take time to get the appropriate technician to identify and fix any problem. Maintenance of the heating system at turnaround will reduce the incidence of unwanted heater lock outs; heaters should be more efficient, reducing run times and using less fuel. In addition, incomplete combustion in gas heaters can cause a threat to human health and safety as carbon monoxide levels build up.
Settings in the environmental control system should also be checked as rogue settings can cause excessive heat burn times and compromised air quality through over or under ventilation. Ensure the house thermostats are accurately calibrated. All sensors should be placed at the same, correct height at bird level and independent alarms set at 2-3 °C below the desired minimum temperature setting to alert managers to incidences of malfunction.
Drinker management
Poor drinker management can affect litter quality. It is important that during turnaround drinkers are checked so that they hang at an equal height from the floor at all points in the shed. Drinker lines should be adjusted so that nipples hang vertically, ensuring the seat of the nipple is sealed and reducing excessive leakage. Water pressure should be adjusted so that birds can drink efficiently. Too low drinker lines will increase spillage as birds can knock the nipples and when they try to drink, water can run down their neck rather than them actually drinking it.
Bedding material
There are many types of litter material that can be used, the most popular of which is wood shavings. These are easy to manage as they break down relatively quickly, and a good depth of litter can be achieved. It is important that bedding material is placed on a dry floor and spread evenly. Litter which is spread evenly also eases drinker management and thus water availability for all chicks. If you are being penalised for poor bird quality it may be beneficial to use additional bedding material for winter.
Often litter under an intensive light source can deteriorate as the "spot" of light encourages bird activity and birds will scratch litter away. With little or no bedding material left there is a build up of droppings which can cause surrounding litter to go off. Bare floor areas are often associated with cold air dropping from the ventilation system and any such areas should be re-covered by moving litter or adding more bedding material.
Ventilation systems
The basic principle of winter ventilation is to draw cold air into the house at the correct speed, allowing warming and mixing before air falls to bird level. Make sure the minimum ventilation is correctly set as prevention is better than cure. Litter problems, due to poor ventilation, tend to occur when air speed through the inlet is too slow and cold air drops onto the litter causing capping down the sides of the house.
Standardise and equalise inlet vent settings, as air will travel via the shortest route between the inlet and the outlet. Uneven inlet settings will give uneven airflow and thus uneven temperature distribution. Exact air speed and pressure requirements to create the desired circulation of air within a house will vary depending on house width. If the inlet air speed is too fast, air will take a more direct route to the fans leaving 'dead spots' within the house. It is also important to seal any gaps such as around doors, to prevent localised chilling which will stunt growth.
Air volume
Calculations should be checked and revised on a daily basis to ensure sufficient air is supplied to meet the birds' physiological needs. Ventilation must be calculated for actual live weight not flock age. In winter when air speeds need to be higher it is important to consider the volume of air being moved when fans are running. Under higher negative or positive pressures, fans become less efficient. Always follow the manufacturer's guidelines for fan capacity at a given pressure.
The ideal way to ventilate effectively is not to give all the air requirement in one go by purging the air, as heaters may not cope with warming a large volume of cold air. To keep the birds in their thermoneutral zone, ideally a cycle of 5mins or less should be used, providing a regular refreshment of air and ensuring that temperature variance and heater run times are minimised. The opportunity to ventilate well on a mild day should be exploited.
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