Cold Weather Preparation

Today’s broilers have huge genetic potential and can reach their target body weight sooner and on less feed than ever before.

In 1967, Cobb produced the first target performance supplement for broilers. Then the as-hatched target for a 2.27 kg (5 lb.) broiler was achieved at 69 days with a feed conversion of 2.5; today the same bodyweight can be achieved in less than 36 days with a feed conversion of 1.55. This reduction of 33 days and using over 2 kg less feed has reduced the cost of producing chicken meat and has made it an affordable protein for all.

The United Nations Food & Agriculture Organization (FAO) predicts that by 2050, 11 billion people will live on this planet and the demand for food will increase by 70 percent not only because of population growth, but also economic development of poorer areas, with 90 percent of this increase in food production coming from technology that will lead to increased yield. Broiler meat production is ideally placed to meet this demand.

To achieve the genetic potential of today’s broilers, it is vital to achieve optimum development during incubation and the first 10 days on the farm. Then embryos/chicks do not have the ability to control their internal body temperature and are therefore are “cold blooded.”

During winter and periods of cold weather the management of these “cold blooded” chicks’ is more difficult and requires precise management. Important measurements should be made and specific goals achieved, such as seven-day bodyweight 4.4 times the day-old chick weight and seven day mortality less than 1 percent.

Antibiotics were used in the past by some to control opportunistic pathogens that could negatively affect the health of the broiler. With tighter controls on the use of antibiotics, it is even more important to adopt the correct management throughout the production chain to achieve antibiotic free production.

Firstly, we need to start with a good quality chick, which will meet these criteria:

  1. Chick yield must be between 66 percent to 68 percent (chick weight as a percentage of initial egg weight) — a vital measurement to achieve early chick weight gain and low chick mortality in the first seven days
  2. Chicks must have closed feathers on their wings at placement„
  3. Chick legs should feel waxy and moist to touch — veins not visible and protruding„
  4. Hocks should be free from abrasions and not blood red in color„
  5. Chicks should have long fluffy down and be bright yellow in color„
  6. Beaks should not contain any blemishes or red dots
  7. Chicks, when turned on their backs, should regain a standing position within three seconds
  8. Chick navels should be clean and well healed — a slight abrasiveness is allowed
  9. Chicks that have defects like missing eye, or blind, poor leg development or cross beaks are culls and should not be sent to the broiler farm

Chick holding rooms in the hatchery and chick transport are often overlooked, but failure to maintain optimum conditions will stress chicks and lead to poor chick activity and early feed/water intake when placed on the farm.

Chick holding room temperature should be maintained between 24 degrees C to 26 degrees C with a relative humidity of 65 percent, and these conditions should be reached and stabilized before chicks are placed in this room. Paddle fans can be used to recirculate heat and create a uniform environment, but should always direct air up towards the ceiling and not on to the chicks, which might cause drafts and chilling.

The chicks should be checked hourly in the boxes, observing chick boxes at the top-middle and bottom of the trolley and feeling the chicks’ feet temperature by placing them against your neck/check; chicks’ feet should never be cold. Blue lights are often employed in the area to reduce stress on the chicks. Chicks should be stocked in plastic boxes at a minimum of 21 square centimeters per chick.

During chick transport, temperature in the chick box should be maintained at 32 degrees C with a vehicle temperature of 25 degrees C (plus/minus 1 degree C). On arrival to the farm, the chick truck should be faced away from the prevailing wind with the chick box unloading conducted at a pace that prevents chick trollies waiting outside in the cold environment unnecessarily.

You cannot properly ventilate or control temperature if the house is not sealed correctly (has air leaks). To test the effectiveness of how well any house is sealed, first close all the inlets, then open an outside door slightly ajar or crack open an inlet and run a fan capacity with 18 cubic meters hour/square meter of floor area. If the house is adequately sealed, you should record a pressure in excess of 37.5 Pascal’s. If less than this, it indicates that the house is poorly sealed and you must seal the house before the correct operating pressure can be achieved. All doors and unused fans during brooding should be sealed outside using plastic sheeting.

At all times during the life of the broiler the following air quality standards must be achieved:

Oxygen > 19.6 percent

Carbon dioxide < 0.03 percent/3,000 ppm

Carbon monoxide < 10 ppm

Ammonia < 10 ppm

Inspirable dust < 3.4mg/m3

Relative humidity < 70 percent

The minimum ventilation system should maintain correct air quality in the broiler house at all times. This part of the ventilation system should operate separately from thermostat control and ideally on a timer that is in total a five-minute cycle. The minimum run time for the timer should be at least one minute to ensure adequate ventilation and litter before the fans go off. The total fan volume required for minimum ventilation should be able to remove all the air in the house in eight minutes or less.

Inlets are a critical part of your ventilation system, especially in winter time/cold weather brooding. If the fans are the ‘engine’ then the inlets are the ‘steering wheel’ of your ventilation system. It is the inlets that are responsible most for correct distribution of air in the house.

Inlets must completely seal when closed and always be wind protected on the outside to prevent the house becoming pressure positive when outside winds are high. If the house has positive pressure, hot air (lighter air) will be evacuated increasing heating costs.

The inlets should be placed as close to the eve height on the side wall of the house as allows easy air movement to the center of house and avoiding any interruptions on the ceiling that may direct air downwards towards chick level. Air speed on entry to the house depends on the width (the distance) the air needs to travel to get to the middle of the house before falling to the floor level. All inlets need to open at least 5 cm (two fingers width); inlets open less than this will indicate that too many inlets are open.

Controlling humidity

The main aim of controlling relative humidity is maintaining dry friable litter. Wet or capped litter will increase carcass issues such as podo-dermatitis and hock burn, and in extreme situations even breast blisters. In Europe, podo-dermatitis scoring is used as a measurement of flock welfare and when maximum permitted levels of podo incidence are exceed in a flock this leads to a reduced number of birds permitted on such farms.

Moisture is produced by the heating system, drinking system and the birds. To reduce relative humidity, the only option is to increase the air temperature — approximately for every 1 degree C we heat the air, the relative humidity of the air is reduced by 4.5 percent. Warm air is lighter than cold air and the warmest air in the building is closest to the ceiling.

The longer we can keep the outside cold air close to the ceiling, the better the opportunity of increasing the temperature of that air and therefore reducing its relative humidity or increasing the moisture carrying capacity of the air.

For example, air at 5 degrees C can hold 6.4 ml of water per cubic meter of air before saturation point is reached — and therefore condensation develops — whereas at 30 degrees C air can hold 32.4 ml of water per cubic meter of air before saturation point is reached or five times the water.

Another way at looking at this is air at 100 percent relative humidity at 5 degrees C which is then heated to 30 degrees C now has a relative humidity of 20 percent. So cold air when heated and expanded has a great potential for carrying water and removing this water from our chicken house as long as we heat it and remove said air.

Seventy percent to 75 percent of the water consumed by the bird will be excreted to the air or the litter. It is the job of the ventilation system to remove and prevent a moisture build-up in the house by heating the incoming air adequately, mixing it with the warm air close to the house ceiling, and removing that moisture-laden air through adequate air exchange (minimum ventilation).

Because of chicks being “cold-bloodied,” in the first days on the farm they require an external heating source to maintain internal temperature control. Three temperatures should be monitored and controlled during the brooding period:

Internal chick temperature
Floor temperature
Air temperature (and its relationship with relative humidity)

Measurement of internal chick temperature can be measured by using a child’s ear thermometer and placing it gently inside the chicks’ cloaca. Ideally chick internal temperature should be 40.5 degrees C (105 degrees F) and maintained in a range of 40 degrees C to 40.5 degrees C (104 degrees F to 105 degrees F).

Achieving correct floor/litter temperatures before chick arrival is critical as the chicks tend to lose significant heat through their feet. When chicks’ feet become cold their internal body temperature reduces, leading to reduced activity as the chick tries to conserve energy, but this leads to reduced feed/water intake and therefore growth rate is compromised and flock uniformity also declines.

At day old an average broiler flock has a CV of 7.88 and the aim of the stockman should be to maintain a flock CV of between 8 to 10; the establishment of a broiler flock CV is hugely influenced by environment and management during the first week. To achieve adequate floor temperature prior to chick arrival, pre-heat the house for 48 hours to achieve a litter temperature of 32 degrees C minimum; if the house has a concrete floor, a minimum concrete temperature of 28 degrees C with target air temperature should be achieved and stabilized for 24 hours before chick placement.

Since litter temperature is often measured quickly at chick placement in a few random areas, the readings do now show how uniform litter temperature actually is. The best way to judge how uniform the litter temperature is in a broiler house take a reading every six meters the length of the house and in three rows across the house. Using Excel, a contour graph can be produced showing how uniform litter temperature is at placement.

Air temperature should also be monitored and carefully controlled during the brooding period. Minimum house temperature should be maintained within 1 degree C of set temperature at all times. Adequate heating capacity is needed with forced air heating. Where winter outside minimum temperatures are above zero degree C, at least 0.07kw/hour per cubic meter of house volume is required, and where the outside winter temperature is below zero, 0.10kw/hour per cubic meter of house volume heating capacity. All sensors should be placed at chick height and calibrated before each chick arrival.

Chicks from pre-peak breeder flocks are smaller and need more external heat to maintain their optimal body temperature compared to larger chicks. Smaller chicks have increased surface to body weight ratio and therefore body heat loss is greater than larger chicks.

At all times, the chick holding room, chick transport and brooding management are vital management areas to ensure optimum broiler performance, and in cold weather these areas are more difficult to control. Failure to understand, measure and record the environment that both the embryo and chick are exposed to during the first week will reduce flock performance and uniformity.

Matthew Wilson is technical manager with Cobb EMEA.

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