Johnny Harrison
Technical Service Manager,
Aviagen Limited
The first article in this series described the key management points needed to start the day old breeders as well as possible (Zootecnica International, February 2006). In addition to measurements of liveability, we defined good brooding management in terms of the flock achieving the Ross target bodyweights each week. There was also guidance on uniformity management – how good brooding management can help to keep flocks uniform, and how to regain any lost uniformity by grading at 28-35 days.
After grading, a flock of 10,000 females should be in 4 groups of about 2500 each (less any mortality). One group will hold all the smallest birds, two will hold all the birds close to target weight and the final pen will hold all the largest birds. If the grading has been carried out as was suggested in the last article, the uniformity in each of the four pens will be around 7-9%.
Objectives for rearing from 28 to 105 days
Management of growth and flock uniformity are the main concerns of this stage of the rearing process. The development of the different tissue groups occurs in phases, as shown in the diagram. Most of the growth of the skeleton, and it's associated connective tissue takes place in the first 10 weeks. It is important to manage the flock so that the individuals within have very uniform skeletal growth. Once this is achieved, then later growth management will be on a consistent frame and it will be very much easier to achieve not only uniform body weights but also uniform conformation.
To achieve the main objective, it will be necessary is to manage the growth of each group of birds such that by 10 weeks of age, every female pen is back on the target weight of 1060g, with each pen very uniform (7-9 % CV or 85% of the birds within +/- 10% of the pen average weight). When all the pens are finally mixed together again at transfer, the whole population must have a CV of 8-9% or less.
Bodyweight uniformity and skeletal uniformity are therefore of equal importance, because the birds will then respond to any stimulus in a predictable way. This is important for a lot of reasons, from vaccination (stimulus of the immune system) to the various triggers used to bring the flock into lay. Good uniformity will produce flocks which are generally healthier and go on to produce more and better quality, uniform chicks.
After grading, uniformity inevitably starts to deteriorate again. The rate of deterioration will largely depend upon the quality and management of the feeding system used. The aim should be that every bird in the pen has simultaneous access to an equal share of the day's feed allowance for that pen. In practice, this does not often happen.
The bigger the pen and the longer it takes each bird to get access to its share of the feed, the more quickly the uniformity will deteriorate. Most problems associated with bird management come from the limitations of flock housing and management systems, and their inability to ensure each and every bird receives identical treatment.
Competition between birds for feed will occur from a number of different causes. The most common include:
- Keeping the birds in over-large colonies (the smaller the better; everything becomes more difficult to achieve in very large colony sizes)
- Track feeding systems which take too long (more than 3 minutes) to circulate around the pen
- Tracks which move through different pens. These make it impossible to manage the feed allocated to each pen,
- Poorly adjusted pan feeders which have different amounts of feed in each pan,
- Too much feed space, so that the feed runs out before it has gone all around the pen,
- Inaccurate feed weighing systems,
- Inaccurate birds counts or poor pen security, so that it is unclear how many birds are being fed in each pen
Feed quality plays an important role and there has to be a balance between nutritional quality and volume. This is because it is possible to give more feed when a lower density diet is given, making feed distribution easier, but good pellet/crumb quality is more difficult to achieve with lower density feed.
Often, the problems of achieving uniform feed distribution of low volumes of feed in track feeders has been resolved by reducing the frequency with which feed is offered to the flock – feeding every other day (skip a day) or 5 days out of 7 (5 and 2).
However, floor feeding, using spin feeders and good quality durable pellets is being found to be an easily automated and managed way of distributing small amounts of feed every day and this method is becoming increasingly popular and common in Europe.
Achieving a smooth growth profile is also important and this is achieved by an accurate weighing (twice a week) and using this information to make decisions about feed allowances. The ideal is to give regular small (1-3g) feed increases. When pens of birds have an average weight above or below target, the target should be modified to take them smoothly back to the Ross target by 10 weeks.
Weights drawn on a graph do not give all the information needed to manage the flock well – handling the birds in each pen regularly is also important. This is the opportunity to check fleshing on the breast and feather cover. Regular handling and inspection of the birds is an important component of good stockmanship – using the experience and good judgement of the manager to see if a bird is thriving before making any changes to management.
At 10 weeks a final grading should take place through all the pens, aiming to place any remaining small birds in one group. This should be the last time any birds are moved.
At 15 weeks, all the birds in the flock should be on or close to target weight for age (1525g with an 8% cv).
After 15 weeks, the birds need to grow more rapidly, preparing themselves for sexual maturity. The flock needs to be sufficiently heavy at first light stimulation to respond to the stimulus. If they are not, egg size will be very uneven, the flock will produce a high proportion of double-yolked and soft-shelled eggs and persistency will be poor.
Therefore, after 15 weeks, female body weight gain needs to become progressively greater week by week, from 90-95g/week at 15 weeks to 175g at point of lay. This change is initiated at 15 weeks by a large feed increase of 10-15% and this must not be forgotten.
Management of the flock from 15weeks, through transfer to the lay farm to first egg will be covered in a next article.
