Chick processing

The chicks are now hatched and ready to be processed. But even a good hatch can still be spoiled. Hygiene, careful handling and attention to the chicks are essential to maintain the best quality. Chicks will tell you by their behaviour and noise whether they are feeling well or not. If they don’t, the problem needs to be investigated and resolved.

Scientific trials as well as hatchery and rearing practice have shown that a chick’s body temperature is an indicator of its well-being. Occasionally measuring the rectal temperature of a representative sample of chicks can help identify weak points in the process and thus help guarantee chick quality. The rectal temperature of a day-old chick measured by an infrared ear thermometer should preferably be in the range 39.5-40°C.

Checking the temperature of the chicks immediately after extraction provides information on conditions in the hatchery. This can be used to adapt the temperature profile if necessary for the next hatch. It is normal for the chicks’ body temperature to drop temporarily during sexing and vaccination. After treatment, when the chicks remain in boxes in the holding room, body temperature should return to the optimum range.

Chick extraction and sexing

All of H&N International’s commercial varieties are either sexable by colour or by feathers. If the breed allows sexing by colour, this is usually carried out directly at chick extraction, whereas sexing of other breeds is carried out as a second process. Readers interested in more information on sexing are referred to the appendix of this guide.

To achieve optimum conditions during take-off, the following recommendations should be taken into account.

• There should be a separate room for chick take-off to keep the down away from the vaccination of the chicks.
• From a hygiene point of view, manual chick extraction is preferable to the use of a separator.
• Do not remove too many trolleys at once. It is common to find that chicks overheat when chick trolleys are waiting in an aisle or other storage area with insufficient air movement.

Video

Vaccination of day-old chicks

Chicks can be vaccinated at the hatchery by injection, spray or drip. Irrespective of the route of administration, three different factors influence the success of vaccination:

• 1. Physical factors – needle damage/cooling/spray particle size
• 2. Contamination
• 3. Under/overdosing (inappropriate vaccine strain).

Each laying chick is vaccinated by injection against Marek’s disease. Several vaccines from different producers are available. Check your country’s requirements.

The Mareks vaccine virus is cell-associated. This means that the virus is grown in tissue and the live cells are harvested and frozen in liquid nitrogen for preservation. The viability of these cells must be maintained throughout preparation and injection in order to maintain the correct vaccine titre. If the cells are killed due to inadequate temperature or rough handling (by squeezing them through small needles), the titre will decrease and the chicks will not receive the required dose of vaccine.

Here are some practical guidelines:

• There should be dedicated clothing for people working in the vaccine preparation room.
• The nitrogen tank must be checked regularly and recorded in a logbook.
• Do not remove the entire can from the vat.
• Expose only the bulb or bulbs to be used.
• Thaw the ampoules in a water bath at 27°C, shaking them gently.
• It’s best to use distilled water in the bath (or fresh, clean tap water), and to change it daily.
• Once the vaccine has become liquid, remove the ampoule from the water bath.
• Use a new sterile syringe with a new needle (18 gauge).
• A maximum of 5 to 6 ampoules should be prepared at a time.
• Dry the bulb before opening.
• Never refreeze a thawed vaccine.
• The diluent must be clear, not cloudy.
• Gently aspirate the vaccine from the ampoule and add to the diluent bag.
• Complete the entire process (thawing + addition to diluent) in 90 seconds or less.
• Shake gently and invert the bag of diluent several times.
• Record the time of preparation on the diluent bag.
• Store ready-prepared bags at 15-25°C.

During administration of the vaccine, it is important to:

• Use sterile infusion kits.
• Use the vaccine within 2 hours of preparation.
• Do not allow contaminated air to enter vaccine bags. Use air inlet filters.
• Keep the vaccination equipment clean throughout the incubation day.
• Change the hands frequently (every hour).

In addition to vaccination against Marek’s disease, spray vaccination against infectious bronchitis is often carried out at the hatchery. Before use, the vaccine is dissolved in water, after which it expires within a few hours. It must therefore be used immediately after preparation. The water serves as a transport medium for the live virus to the chicks.

• Once sprayed, the virus will attach itself to the mucous cells of the chicks’ eyes and upper respiratory tract. Cleaning the feathers with the beak will optimise absorption.
• Lors de la vaccination par pulvérisation, il est important que la taille des gouttelettes ne soit pas trop petite (au moins 100 à 150 microns).
• The spray should not resemble vapour. Such small droplets will be inhaled too deeply, which can lead to post-vaccination reactions.

When preparing the vaccine, it is important to have equipment dedicated solely to this purpose. Any disinfectant present can kill the virus. Make sure that the water is of good quality (no chlorine, low mineral content) and that all chicks are sprayed evenly.

Holding and transporting chicks

The behaviour of the chicks is the best indicator of the climatic conditions in which they are kept and transported. In optimal conditions, chicks are generally calm, breathing calmly through their nostrils and evenly distributed in the boxes. If it is too hot, chicks will start to pant, leading to increased moisture loss and dehydration. If it is too cold, the chicks will huddle together. Chilling is likely if wet chicks (taken out early, spray vaccinated) are placed in a store with high air velocity or too low a temperature.

In general, an air temperature between the boxes of 25 to 27°C (77 to 80°F) and a relative humidity of 50 to 60% are recommended. However, it’s not the room temperature but the temperature inside the boxes that is crucial to the chicks’ well-being. Usually, this should be between 33 and 35°C (91 and 95°F). The optimum room temperature will vary depending on the air movement in the room, the type of boxes, the way they are stacked and the number of chicks per box. To give the chicks a good rest, the holding room should be kept dark. Light should only be provided if the chicks have been fed.

It is advisable to check conditions during storage and transport using a data logger.

If the chicks are scheduled for a long journey, they benefit from extra moisture, which can be administered during vaccination without any additional handling. When applying the injection subcutaneously, the volume of the diluent can be increased to 0.5 ml. Of course, the vaccine dosage must remain the same.

 Therefore, a different size of diluent bag should be used. The volume for an intramuscular injection should not exceed 0.2 ml to avoid tissue damage.

Get the basics right

• 1. Always pay attention to the chicks’ behaviour. This is the best indicator of their well-being.
• 2. Prepare the vaccine in a separate, clean room.
• 3. Do not allow unfiltered air to enter vaccine bags or bottles.
• 4. Keep vaccination equipment clean throughout the incubation day. Change needles regularly.
• 5. The temperature of the chick processing and holding room should be approximately 25°C (77°F).