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By Dave Watts, Regional Accounts Manager, Aviagen
Control of Egg Size, Female Body Weight and Persistency of Lay
Due to emphasis placed on early broiler growth rates, over the next 6-12 months, we can anticipate a small increase in egg size in Ross 308 Parent Stock; though not a major increase it will need to be managed to avoid possible problems in the hatchery.
Female bodyweight and egg weight progression must be major priorities in the period from 30-60 weeks. Recent research by Aviagen has shown a positive correlation between egg size and persistency of lay.
The data shows that; if persistency falls then egg weight rises as in 308-4.
Maintaining bodyweight profile and persistency is achieved by programmed feed reductions.
The timing and amount of feed reduction will be dependent on many factors:
- Bodyweight and bodyweight change from start of production
- Daily egg production and trend (hen day)
- Daily egg weight and egg weight trend
- Changes in "eating up time"
- Health status of the flock
- Ambient temperature
- Feed composition (i.e. energy and protein level) and quality
- Quantity of feed (i.e. energy intake) at peak
- Flock history (i.e. rearing and pre-peak performance)
Since there is variation between all flocks in the characteristics above, the programme of feed reduction will also vary for each flock.
General guidelines for feed reduction are:
- 27- 34 weeks - hold at peak feed
- 35-50 weeks - gradual reductions down to 412kcal ME/bird/day (150g/bird/day) minimum
- 50 weeks - hold feed levels
Routines should be established which allow the following to be monitored and used in the decision making process:
- Weekly body weight and body weight change of 15-20g/bird/week calculated over a 3-4 week period
- Daily egg weight and egg weight change relative to target egg weight
- Physical condition i.e. Fleshing and muscle tone; fattiness; feather cover and condition; leg and feet condition; wattle, comb and face colour; general production levels
Feed allowances should be adjusted to compensate for unexpected changes in the above characteristics. In extremes of temperature it may be necessary to adjust feed allowances according to the bird's energy requirements.
Failure to control body weight from 30 weeks will significantly affect persistency of lay, egg size, shell quality and female fertility post 40 weeks.
Egg Handling
The egg takes around 22-24 hours to get from the ovary through to ovulation. Cell division begins to take place as the egg travels down the oviduct. At the time of lay the germicidal disc will contain up to 60,000 cells and these will have begun the process of organisation into groups.
The laid egg contains a living organism. It is therefore crucial to remember that inappropriate handling or storage conditions from the moment it is laid may dramatically reduce the chances of it producing a healthy chick.
Normal cell division will continue above 27ºC and slows down below 26ºC. This process stops completely at 21ºC; this point is known as Physiological Zero. If cell division continues beyond approximately 5 hours after lay, the egg is less likely to hatch as a result of increased early embryonic death.<
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Procedures should be established to ensure uniform cooling of eggs to 20-21ºC within 4 hours from the time of collection from the nest. Frequent egg collections will allow eggs to reach Physiological Zero at similar stages of embryonic development. Automatic nests should be run at least 3 times per day and manual nests should be collected at least 4 times per day.
Auto Nests
The environment on the belt is unlikely to be suitable for holding eggs for any length of time. Depending on the layout, the belts may be either very warm (above physiological zero) or cold (which encourages condensation on the egg surface).
Belts and nest pads should all be kept clean and a regular routine of cleaning should be practised. When belts are cleaned, care must be taken to ensure that the belt is dry before it comes into contact with eggs. During the times that the nests are not being run, the ends should be blocked off as these can act as a wind tunnel and chill any eggs on the belt.
Auto nests will reduce the number of staff required, but as with any system effectiveness should be carefully monitored. Routines should be established to ensure that the maximum numbers of eggs are laid in the nests. The equipment must be maintained to minimise losses due to mechanical damage of eggs during collection and grading. Auto nests are an aid in reducing labour, not a reason to keep out of the stock.
Belts should be run at least once a day two weeks before the onset of production; this allows the birds to become accustomed to the noise.
Floor Eggs
Unfortunately there will always be a percentage of eggs laid on the floor; the level will depend on several management factors.
- Introduction of perches in rear from 6 weeks of age
- Incorporating a suitable alighting rail in the nest box design
- Ensuring that males and females reach sexual maturity at the same age
- Uniform distribution of light of greater than 60lux
- Correct feeder space for females i.e. minimum 15cm/female
- Lighting the birds in synchrony with achievement of target body weight gains
- Effective management of early mating ratios; over mating can predispose floor egg laying
- Set feeding times to avoid the peak of egg laying activity. Feeding time should be either within 30 minutes of lights on, or 5-6 hours after lights on, to prevent the majority of hens coming off the nest to feed
- Regular collections of floor eggs at the onset of production (> 10 times per day)
A DIRTY EGG IS NOT A HATCHING EGG A DIRTY EGG IS NOT A HATCHING EGG
Egg Storage
Once collected, the eggs should be in a controlled cool environment within 30 minutes.
- Some common farm problems are:
- Eggs left in the nests getting re-warmed when the nest is occupied by another bird
- Poor ventilation of a roll away auto nest so that temperature is above 27ºC
- Eggs packed onto fibre trays which allow very slow cooling (> 6 hours)
- Eggs held in the house until the end of the day or, on occasions, a part trolley left overnight until it is filled the next day
- Doors left open during hot/ cold spells
- Insufficient temperature control due to poor insulation or cooler capacity
- Poor air circulation
- Trolleys held outside prior to loading
Correct temperature and humidity during transport and storage are important in achieving maximum hatchability. The appropriate conditions are shown below.
Temperature and Humidity in Relation to Storage Time
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Days
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Temperature (ºC)
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Relative Humidity %
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1-3
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19
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70-75
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>4
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16-18
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70-75
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Lower temperatures for longer storage help to maintain internal egg quality.
Correct movement of air as described above is essential to achieve and maintain the humidity and temperature with minimal variation (+/- 1ºC throughout the entire storage area and period).
- Too high a temperature will encourage bacterial growth
- Too cold and there is a danger of condensation
- High humidity will encourage fungal growth
- Too much air flow will cause too great a fluctuation in temperature
- Too little air flow and the eggs can re-warm
- The egg dispatch area should be sheltered from the elements
Miniature temperature loggers are invaluable for tracking this exercise and allowing identification of the stages that require attention.
The storage area must be large enough to hold the anticipated volume of eggs and to meet the egg spacing requirements (a gap of 40-50cm between walls and between rows of egg trolleys). The ceiling of the store should be approximately 1.5m above the stored eggs.
Egg Hygiene
Careful attention to hygiene will improve hatchability and chick quality. Bacterial penetration of the shell will result in higher levels of early dead, weakened embryos, higher percentage of culls, yolk sac infection, higher first week mortalities, more dead in shell and bangers so contaminating more eggs in the hatchery.
Critical areas to be monitored are, nest material; pad and belts; egg trays; floor eggs; egg markers; fogging systems; humidifiers; cooler grills; egg rooms and stores; fan blades, etc.
Ideally eggs should be disinfected immediately after collection, whilst still warm. As the egg cools its contents contract and any bacteria on the shell will be drawn into the egg through its pores.
Cleaning eggs with sandpaper, wire wool or a knife will have a negative effect by grinding the bacteria into the egg. A clean egg is one that has never been dirty.
There are many ways of disinfecting hatching eggs. Whichever way is chosen, it must:
- Be capable of a bacterial kill rate of > 90%
- Be harmless to the embryo
- Be safe for the operator
- Leave the cuticle undamaged
- Leave the shell dry
- Not submit the egg to extremes of temperature
It is a fact that floor eggs have to be used. These should be kept separate from nest eggs and preferably should be placed on the bottom of the egg trolleys and marked as floor eggs.
The egg's function is to provide the developing embryo with nutrients, protect it from physical damage, bacterial infection and optimum positioning of the embryo in the shell.
For such a delicate object to hold such a valuable commodity, a little extra help from us does not go amiss.
Courtesy of Poultry World, May 2004
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