Rearing Parent Stock

By Johnny Harrison, Technical Service Manager, Aviagen Limited - This article follows the life of a flock of Aviagen parent stock birds, focusing on the rearing period, 0 - 6 weeks, (0-42 days).
calendar icon 11 September 2006
clock icon 11 minute read

Aviagen produce a range of genotypes suitable for different sectors of the broiler market and all Aviagen products are selected for a balanced range of parent stock and broiler characteristics. To achieve the best possible outcome, and to meet the needs of your operation, the best possible start must be provided to both the male and the female parent. Fulfilling all of their requirements during the rearing period will prepare them for sexual maturity.

Aviagen parents have the same growth and feed efficiency characteristics as the broiler generation, so growing the Aviagen parent to the target growth curve allows both males and females to achieve optimum lifetime breeder performance. The principles for managing males and females in the rearing period are the same, even though the target body weights are different. Although males constitute a small percentage of the flock in terms of bird numbers, they will form 50% of the breeding value. Males are therefore just as important as females; however throughout the rearing period the management of males will require more effort to achieve success.

Managing the available feed is crucial in ensuring even distribution to all of the birds and this is one of the main management challenges during rear. Managing the birds' growth rate so they achieve the target bodyweight for age is maintained through accurate control by sample weighing at least twice a week until grading and adjusting feed allowances accordingly. As a result accurate grading will aid good uniformity.


FIGURE 1: Bird Distribution under Brooders

As outlined in the Biosecurity article (Zootecnica Russian Edition, Feb/Mar 2006), houses and equipment must be cleaned, disinfected and set up in time for the brooders to be started and temperatures to reach the desired level 24 hours before the chicks arrive. The house should be checked to ensure that it is adequately light proofed. Birds are very sensitive to day length and any accidental seepage of light should be corrected immediately. Match the times when house lights are on to the natural day light as far as possible to limit the impact of poor light proofing. Problems such as early on set of lay, broodiness and prolapses or delayed production may result from poor light proofing of the rearing house.

Temperatures should be checked at chick level. If insufficient time is allowed for floor temperature to reach house temperature, there is a danger that the chicks will become chilled. Chick behaviour is the most important indicator of temperature, farm managers and farm staff must respond quickly to changes in chick behaviour. The photo right demonstrates chick distribution.

Fresh litter, free from dust, should be laid to a depth of 10cm. Where floor feeding is in use litter depth should not exceed 4cm as feed will be lost in the litter. Good quality litter will reduce the risk of the chicks eating the litter.


There are two basic systems to supply heat to the birds:

  • Spot Brooding
  • Warm air/Whole House Brooding

Brooding down the centre of the pen is most likely to achieve uniform chick distribution. Figure 2 shows a typical spot brooding system for 1000 day old chicks. When planning chick placements, it is advisable to brood chicks from young donor flocks separately for the first 14 to 21 days, this will prevent early competition when birds are unequal in size.

On both systems chicks must be placed in the brooding area immediately after they arrive. Full chick boxes should never be stacked within the brooder house as this can cause heat stress. Empty chick boxes should be removed from the building and destroyed as soon as possible. To avoid undue stress vaccination should take place in the brooding area after the chicks have settled in.

The brooding area should be designed to allow the chicks access to a plentiful supply of fresh feed and water upon arrival. Birds given immediate access to feed and water have been shown to have better early growth and uniformity than birds in which feeding was delayed.

A maximum of one day's supply of feed should be provided daily to avoid problems associated with stale food. Chicks should be treated as broilers for the first 5 to 6 days (i.e. fed ad libitum). Feed should be given frequently (i.e. 5-6 times per day) to stimulate appetite.

A plentiful supply of water must be provided, use supplementary drinkers as well as the drinking systems already fitted in the house. Aviagen does not recommend the addition of glucose to drinking water as it can depress appetite and cause dehydration; the goal we are aiming for is developing healthy appetite and drinking behaviour

For the first 24/48 hours light should be continuous, with a light intensity of 100 lux. To encourage even distribution of chicks, the brooder light should be raised initially, followed 2-3 days later by switching on the adjacent rows of house lights.

The principles for whole house brooding are basically the same, but it is less easy to use chick behaviour as an indicator of satisfactory temperature than with spot brooding, because there are no obvious heat sources. By spending time in both environments you will notice a different noise made by the birds, this may be the only indication of distress. The birds will congregate in the areas where the temperature is closest to their requirements. Some care is needed to interpret chick behaviour.

Chicks must have an adequate supply of fresh air and a minimum ventilation program must be established during brooding. It is good practice to establish a system of minimum ventilation during brooding.

Monitor relative humidity (RH) levels in the first 3 days and aim to achieve around 70%. If humidity falls below 50%RH in the first week, chicks will begin to dehydrate, causing negative effects on performance. In such cases, take action to increase humidity. Various methods of humidification are suitable, from spray systems designed to cool birds in hot weather to simple open water surfaces. Keep the system clean, because it can provide a very effective means of transmitting bacteria.


The aim in this period is to ensure good early development of skeletal size, immune system, cardiovascular function, feather growth and appetite. It is important to obtain the best possible uniformity to reduce the amount of size grading required later in the flock.

To maximise performance birds should be on or over target bodyweight by 7-14 days. Flocks that fail to achieve target tend to lose uniformity. Bodyweight targets in the early stages of rearing can only be achieved by ad libitum feeding of a good quality feed from day old, Crop fill should be assessed to ensure that chicks are developing a healthy appetite and achieving good early bodyweight and skeletal growth, see figure 4.

A full crop will be a rounded mound and it should feel like pea soup, a mix of water and feed. Aim for more than 95% of birds with full crops by 8 hours after first access to feed and water, and more than 99% at 24 hours.

If there is any evidence that birds are not growing to target bodyweight, then the age at which constant day length will be achieved can be delayed


It is essential to monitor growth and development in a flock by weighing an adequate sample of birds and comparing them with the target bodyweights-for-age. The birds must be weighed accurately using conventional mechanical, dial or electronic scales are more labour intensive, but using these systems enables you to handle each bird and check its condition as well as its weight.

Sample weighing should be carried out twice weekly starting at day old; randomly selected samples of birds should be weighed individually. Groups of 50 to 100 birds per colony should be caught using catching frames and individually weighed. All birds rounded up as a sample must be weighed in order to eliminate any bias. Birds should be weighed on the same day each week and at the same time, preferably 6 hours after feeding


Bodyweight can be corrected by adjusting feed allowance. This can either be maintained or increased. Feed allowances must never be decreased during the rearing period. Adequate feed space must be available and feed should be distributed in less than 3 minutes per colony. Good feed distribution, which allows all the birds to have access to feed at the same time, is absolutely essential because the birds are fed at less than ad libitum.

Birds must be fed every day until grading has been carried out. After grading an alternative method should be considered to ensure even distribution of the feed, minimising competition and maintaining bodyweights and flock uniformity. 'Skip a Day' can be used. This is achieved by accumulating sufficient feed on the 'feed day' and supplementing with a scratch feed on the intermediate days.


Uniform flocks will be much easier to manage than an unequal one, because the majority of the birds will be in a similar physiological state and will respond to changes in levels of feed or light when necessary. A uniform flock will react predictably to increases in feed and will produce good results consistently. Flock uniformity can only be achieved by applying high standards of management in the first 4 weeks.

Grading is best carried out when the flock is aged 28 days (4 weeks), at which time the uniformity of the flock is usually within the range 10-14%. If undertaken later than 35 days (5 weeks) the time available in which flock uniformity can be restored, i.e. up to 63 days (9 weeks) becomes too short. In most cases, grading will be undertaken when the flock CV% is around 12.

The practical requirements of grading must be considered at the planning stage, before the stock is placed. The easiest way to grade is into pens or possibly houses which have been left empty at placement for this purpose. To establish successful grading the flock should be sorted into populations of different average weight at 28 days (4 weeks) of age, so that each group may be given the management during the rearing period, which will result in good whole flock uniformity at point of lay. As an example, separating 10,000 females into 4 groups of 2500, less any mortality, will give one group of small birds, two groups of medium birds and one of large birds. The males should be divided into two colonies as it is easier to manage small colonies.

Within the flock to be graded all colonies must be sample weighed and all the individual weighings should be consolidated into a single distribution. Two-way grading is preferable, provided that the flock CV% is less than 12 at grading. If the CV% is more than 12, then a 3-way grading will be required and management practices from 0-4 weeks should be examined closely, so that improved CV% can be achieved with subsequent flocks.

Flock CV% should be calculated. Cut-off points must be set to achieve consistent stocking densities allowing for differences in pen size. Table 2 indicates the typical percentages in light, medium and heavy populations to achieve populations with CV % less than 8 for 2 or 3-way grading. Bird weight cut off points should be set to achieve the required percentage of the population in each colony

All birds must be handled and allocated to their correct category to achieve accurate grading. It is strongly recommended, for reasons of efficiency and accuracy, that all birds should be weighed.

Birds must be counted accurately in order that the correct quantities of feed are provided. Stocking density per colony, and therefore feed and water space must have been routinely adjusted when the moveable partitions were positioned. In addition feeding space, speed and uniformity of feed distribution must be adequate.

Each category should be reweighed to confirm the average bodyweight and uniformity so that its projected target bodyweight and feeding rate may be determined.

Key Points:

  • Prepare, clean and disinfect houses and equipment well in advance of chick arrival.
  • Ensure that the house reaches the correct temperature and Relative Humidity 24 hours before chicks arrive.
  • Ensure that chicks have immediate access to fresh water and feed.
  • Monitor crop fill to ensure chicks are feeding.
  • Use chick behaviour as an indicator of satisfactory brooding temperature.
  • Achieve early bodyweight targets to facilitate successful rearing.
  • Start sample weighing at day-old.
  • Weigh birds at the same time each week, twice weekly.
  • Use accurate bird weighing equipment.
  • Never decrease feed allowance during rearing. Feed allowance should either be held or increased.
  • Give birds the correct feeding and drinking space.
  • Feed should be distributed in no more than 3 minutes per colony.
  • Grade into 2 colonies if CV% is less than 12; into 3 colonies if CV% is greater than 12.
  • After grading, each colony should have a CV% of 8 or less.

This article was first published in Zootecnica Russian Editon, April/May 2006

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