A weekly control of the growth is a must to check the real evolution of the flock: the earlier you know the earlier you can correct.
Targets in rearing:
- To produce a uniform flock and a weight, which is compatible with the intended age at sexual maturity
- To obtain the correct bodyweight at 4 weeks to secure frame development
- To achieve steady growth between 4 and 16 weeks with a good development of the digestive tract
Targets in production:
- To make sure that between 5% lay and peak production the bodyweight increase is at least 300 g. For these reasons it is essential to exercise control over bodyweight on a weekly basis from 0 to 30 weeks.
- Controlling the quantity of feed issued will not on it's own ensure good growth because the requirements vary according to:
- the energy level of the diet the house temperature.
- the health status of the flock
Method of weighting
The time of weighing should be fixed, preferably in the afternoon. We advise carrying out individual weighings. A practical method is to use weighing sheets, which allow us to put the weights straight into a histogram. This shows at glance the weight distribution within the population.
For floor rearing situations, make a lightweight wire netting pen, and then walk into the middle of the flock and surround a group of birds. Individually weigh all the birds in that pen.
A sample with a minimum of 100 birds gives a good estimate of mean bodyweight and uniformity. However, if the flock is divided into separate pens, it is necessary to take a sample of 50 birds from each pen and then to calculate the overall mean. When rearing in cages, one should weigh all the birds from 5 or 6 cages chosen at random in different parts of the poultry house to make up a sample.
- Global weighing between 0 and 4 weeks old. As Uniformity is very difficult to measure during this period
- Weekly individual weighing from 4 till 26 weeks old
- From 26 till 35 weeks old, weigh every 2 weeks
- From 35 weeks old, once a month
The quality of a flock is judged, as much as anything else, by its uniformity. A batch is uniform when all the weights within the sample fall between plus and minus 20 % of the mean or, when 80 % of the weights lie within + 10 and 10 % of the mean.
Within the limits of plus or minus 20 % of the mean, the smallest and the heaviest pullets are of the same quality. Only those birds which are too small should be culled. If uniformity is outside the target range, it is necessary to identify the causes and to check:
- the feeder space and position - the speed of the feed chain
- the quality of beak trimming - the vaccination status
- for disease and parasitism... etc. In all cases underweight birds should be corrected or culled by eight weeks of age.
In cages, we recommend that the lightest birds be sorted out frequently from six weeks and be put in the top row and that checks are made that there is the same number of birds in each cage.