RderCorp North Husbandry Machinery |
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Issues that will be discussed in this article:
Issue #1. The importance of ventilation in the hatchery for the present day high-yielding broiler chicks.
There are basically 3 ways to supply fresh air or oxygen to the setter and hatcher machines: The 1st way is by natural ventilation in open sided hatcheries. This concept is still used in some tropical countries but even there it is phased out due to the inability to constantly control the environment within the machines. Due to the fact that all modern models of setter machines are direct induction (plenum), they need to have an atmospheric controlled setter or hatcher room with positive pressure.
Photo 1: Evaporative cooling Unit on the roof of a hatchery
Ventilation in the hatchery is based on fresh air for the embryos
and chicks, for temperature and relative humidity (RH) control and
to maintain the right room pressures. Evaporative Cooling
Units will only give fresh air and some temperature control under
hot conditions. These units will need to be controlled in 3
stages: At slow speed, at high speed and then with the pumps
running when temperature of incoming air will surpass 28ºC.
The low speed should always be in operation to supply enough oxygen
to the setter and hatcher rooms.
Photo 2: HVAC unit on top of the roof and how they look inside the setter
room (photo 3)
HVAC units do all the important aspects of environment control in
the hatchery: H stands for Heating, V for Ventilation and AC
for Air Conditioning. They also control the air pressure
within the room that is set by a PEC (pressure equalizing control)
unit.
Graph 1: After 12 days of age the embryos start developing fast and oxygen need will rise constantly. It is in this period that ventilation should be optimal in order not to pre-dispose the chicks to respiratory and possible ascitesproblems later on in life.
By controlling the temperature and relative humidity in the setter
and hatcher rooms, the dampers of the machines will for most of the
time be open and the positive pressure in the room will assure that
fresh air will flow into the machines through all the egg mass.
Table 1: This important table basically mentions how to manage the
environment in each room of the hatchery in order to have optimum
quality chicks. Investing in environment often results in
better hatchability but this is not always the case.
Investment in environmental control will be seen mainly at chick
level (quality) and better field performance of the broilers.
Pay back can be very fast based on the local conditions (altitude
for example) and is one of the overlooked areas in many companies.
Issue #2: Ventilation, Temperature & RH control during chick transport.
Chicks that suffer from heat stress for more than 15 minutes will
dehydrate, are more susceptible (reduced immune response) and have
alterations in the intestinal tract reducing GPD in first week and
affecting uniformity of the flock.
Photo 4: Excessive temperatures in the holding area of the hatchery
due to insufficient air flow or circulation and in the chick truck
are probably the 2 main reasons of reduced chick quality arriving
at the farm. Chicks in these cases do not only dehydrate but
are often deprived of adequate oxygen levels affecting the
respiratory tract, which includes the lungs. In traditional
natural ventilated trucks body temperature of the chicks vary from
95ºF=35ºC in the lower part and up to 104ºF=40ºC in the upper part
of the truck body.
Truck Ventilation systems, Maximum Temperatures & required Air
Exchange per 1000 Chicks
Some basic thoughts need to be taken into account with the chick truck.
New designs of chick transport stress the importance of having for
100% of the chicks the right climate conditions (temperature and
RH) so that chicks arrive in optimal conditions at the farm and
maintain FCR in the 1st week below 1:1 and in the 2nd week below 1:1.1
Some other reflections:
Issue # 3: Minimum ventilation in broiler houses.
Minimum ventilation will guarantee fresh air (oxygen) availability to the chicks as of day old to obtain maximum growth rate and organ development in the first few weeks, critical for good end performance of the flock.
It is very evident that minimum ventilation in broilers is a misunderstood management concept in many companies and especially in most tropical and sub-tropical countries. Because average temperatures are high, it is assumed that only tunnel ventilation after 4 weeks of age is needed to control the temperature and get fresh air to the birds.
The problem arises when one, or several tunnel fans are used to control the temperature and get fresh air at bird level in the first 14 days.
With this concept excess air speed over the chicks will result,
causing a chill effect. Feed kcal will in this case be used for heat production and not
for maximum growth rate.
Table 2: Baby chicks in the first 2 weeks of the rearing should
receive almost zero air speeds from the ventilation system.
If only 1 fan ran from the tunnel ventilation system, the airspeeds
would surpass easily 50 fpm, and that is 4 times as much as the
chicks should feel. The consequences are inconsistent broiler
results that most of the time do not get even close to the body
weight (BW) and feed conversion (FC) standards of the breed.
Minimum ventilation can be done in several ways. It is, however, important to realize that minimum, transition and tunnel ventilation depends on good airtight houses with minimum leaks or false air entering the house. Be assured that this will need enough attention when upgrading existing older house facilities.
The following 2 situations are seen very often in the field,
affecting considerably broiler performance.
Photo 5: All fans running in the first week to control the
temperatures, but now excess airspeed over the chicks and chilling
results.
Photo 6: Older broilers that receive too much airspeed (chilling) stay
down on the floor and this effect feed and water intake.
In order to control the temperatures within the permissible range and have at the same time a low airspeed over the chicks ventilation is done over the cross section and not over the length of the house.
Design 1: Explaining the difference in air speed based on tunnel and
cross ventilation.
Design 2: Cross flow ventilation to obtain air exchange &
temperature control at the same time
There are several ways to apply cross ventilation and there are even some hybrid concepts with transition ventilation. If more info is required please contact the author by email.
Issue # 4: How to calculate the number of fans needed.
In existing houses you can calculate backwards and see how much the air speed is in the house (theoretically, then real air speed can be different based on many factors).
Observations on air speed:
Issue # 5 What are the causes of Wet Litter behind the Pads.
Wrong pad area in relation to the total fan capacity.
Design 3: The inlet pad area is determined by the total fan capacity
installed. Only at total fan capacity running should the pump
operate in order to make full use of maximum evaporation. The
pads are calculated to work at maximum efficiency with an airspeed
going through them at 400 fpm (2 m/s). Within the pads a
friction is induced to elevate the temperature of the incoming air
to enhance evaporation of the water and thus cooling of the air
leaving the pad towards the inside of the house.
Dividing the total fan capacity by 400 will give the total area for 6" wide (15 cm) pads in square feet. Divide again by 2 to know the area to be installed on each side of the house. Pads come normally in segments that are 5 or 6' in height.
If the pad area is too small the airspeed will be too fast going through the pads and this will reduce evaporation and more water droplets will enter the house elevating RH and wetting the litter.
If the airspeed is too low through the pads there is just not enough temperature rise (friction) reducing evaporation rate and again also helping to wet the litter on the inside.
reducing evaporation rate and again also helping to wet the litter on the inside.
Photo 7: The inlet curtains will permit that air enters restricted (compressed) into the house. When the air expands (RH will go down) it has the ability to take up more humidity of the house.
The airspeed of the air will also guarantee that the whole area behind the curtains will receive enough ventilation to keep the birds happy and have a uniform bird distribution. Observe that the curtain inlet is more than 1 m of the floor so that incoming air will not hit the birds. That could cause bird migration towards the inlets on hot days and make litter very humid.
Photo 8: Under normal temperature and RH conditions pads of a 30-30
degrees angle should be used. Under very dry conditions
(<30% RH) and high temperatures (>35ºC) a 45-15 angle pad is
used with the 45 degree angle always positioned towards the
outside. If pads are upside down with the 45 degree pad and
directed towards the inside of the house more humidity will be
brought into the house. With the 30-30 configuration it does
not matter how installation is done.
Photo 9: Normally with the RH of the air of 50% the pads operate with a cycle of 3 out of 10 minutes, meaning the pumps will run for 3 and will be off for 7 minutes. The higher the RH the slower the evaporation rate and the less the pumps will need to run to wet the pads.
If pumps run all the time there is less evaporation of the water and the excess wetting of the pads will increase the RH levels in the house.
The largest evaporation rates of water are obtained when the pads are almost dry.
Photo 10: Factors that increase the RH in the house:
Humidistat in the wrong area of the house (should be placed 6 f (2 m) behind where the pad area ends.
Photo 11: Water on the pads preferably should be above 82ºF or 28ºC for evaporation.
Water in underground deposits will have temperature of 70ºF or 21ºC or less.
Pads will be too cold and thus less evaporation but adding RH to the house and killing birds under extreme conditions. A temperature of >25 ºC of the pads is good. Pads should be in full sunlight. The hotter the pads and the water wetting it the more evaporation will take place and the cooler the air. Use products to reduce algae growth on the pads (maintenance).
Photo 12: Pads in full sun. There will be a tremendous reduction in the evaporative cooling effect of pads when they become calcified. Opening once a week the purge line is essential to take out the mineral concentration and it can be done even twice a week based on the hardness of the water.
The purge line should be opened when the pump is running in order to drain the minerals in the vertical PVC purge line. If pads become too hard they function more as a humidifier bringing water into de house and wetting litter. There are situations where the pumps should be running most of the time to keep the pads wet and reduce mineral deposition.
Issue # 6: How to do maintenance on pads to keep efficiency up:
Photo 13: Surfactants are used to clean the pads on regular basis to maintain maximum evaporation capabilities. Procedures for cleaning.
Observations: Adding too much surfactant to the water could cause the pads to collapse due to excess water absorption by the pads and becoming extremely heavy, so be careful.
Surfactants can be purchased very cheap at any store that sells insecticides and pesticides. The product is usually added to enhance the penetrating effect of pesticides on the leaves.
Issue # 7: Causes of air distribution problems through the house and bird migration.
Design 4: Low inlet air speed.
Photo 14: No birds in center of the house.
Photo 15: After 28 days with temperatures over 27 ºC a difference of 2 to 3 ºC from inlet to fan end is considered normal. Heat build up continues going towards the fans absorbing heat from the birds.
No difference in temperature means in general excess air speed.
Issue # 8: How much temperature reduction is possible with pads and
with fogger systems?
Table 3: The following table will give the temperature reduction that
may be accomplished with evaporative cooling when dry-bulb
temperatures and RH are known. With a good fogging system you
can expect about 55% of the table values.
Table 4: gives the sum of temperature and RH as an expression when
birds will be affected by a combination of the 2. For every
2.5 ºC increase in temperature the RH will drop 20%. This
feature is used effectively when the RH is too high. By
letting the temperature increase, the RH will drop considerably,
reducing the sum of temperature and RH and thus reducing the
Effective Temperature Index, avoiding high mortality.