Over the years, selection in poultry genetics has targeted the more productive birds in pursuit of improved meat production, with particular emphasis on efficient feed conversion, carcass yield and weight gain. These characteristics are inversely proportional to production of high numbers of fertile eggs. This requires extra efforts in the rearing period with an emphasis on flock uniformity to get all the birds in production at the same time.
By Paulo Fávero , Technical Service, Cobb-Vantress Brazil
When working with birds that have excellent feed conversion ratios associated with a high weight gain, there is a major challenge in rearing them to achieve good reproduction. To achieve good results with the breeders, we need a high level of skill in rearing the birds, with the focus always on proper uniformity. The main objectives of the breeder rearing period to attain high fertile egg production are:
• Body weight control
• Carcass body composition
• Preparation of the birds for the first light stimulus.
Bird uniformity should be the aim to obtain an even flock. Remember that we always work on a population basis, and if there is a high degree of variation in the flock there will be major problems in providing the correct amount of feed for all birds. Bird conformation should also be considered. There may be two different birds of the same weight — one breeder may have a small carcass but a large muscle mass, while a second breeder may have a large carcass but with very little muscle mass. Although both birds have similar weights, their body composition will be quite different.
Critical factors Weight gain in the first week of life is the initial challenge, as this is when the birds must express all their weight gain potential. Because of this, housing conditions should be the best possible; monitor closely the area where the birds are housed, provided with feed and water, and kept at the proper temperature. Several studies have shown that birds exposed to low temperatures, or to major temperature variations, in their first week of life have lower weight gain rates, which will certainly compromise performance, especially in terms of uniformity. The space provided for the birds is directly related to the capability of the equipment used. This area should be heated, and the smaller the area, the lower the birds’ energy expenditure through unnecessary travel.
Feed distribution is a critical issue in management. The constant pressure to enhance production can lead to placing more birds in the rearing areas, resulting in an increase in density and so a decrease in feeder space available to the birds. This makes it more difficult to rear them well. Adjusting the feeder space according to the age of the birds is a good way to facilitate their growth, since the carcass grows at a significant rate until 12 weeks of age; however, in the first weeks, since we are working with small amounts of feed, the larger the trough space available to the birds, the greater the likelihood of errors in feed supply.
In addition to space, be aware of the time difference in access to feed between the first and last birds in the circuit, which should be no more than three minutes for full distribution, (ie, to “close the turn” of the feeder) the shorter the distribution time, the better the results. To achieve this, new feeder models have been created or adjustments can be made especially since larger houses and longer feed runs make feed distribution a time-consuming task if done in the conventional way.
Selection and weighing During the breeder rearing phase, selection has been used to standardise flocks and adjust them for proper development; however, major hurdles may have to be faced in implementing this with any lack of skilled labour. Breeders that perform best go through a selection or grading process at different ages. The first selection is done at seven days using a digital scale, then repeated every four weeks using conventional scales until the last selection at 16 weeks based on a fleshing analysis.
Another critical factor that has not helped achieving better results is the weighing process itself. The main purpose is to show how the females are developing based on feed increments and distribution, if weighing is not done properly, the birds will be handled incorrectly and this itself may delay their development.
Keep in mind that a balance between bird carcass size, accumulation of muscle mass and fat deposition on this carcass should be adjusted according to bird age so you can achieve the proper body composition and thus make the birds fully capable of producing fertile eggs. It is more difficult to grow birds that are very large in the early stages, as they will always be overweight – a fact that usually leads to decreased food stimuli and results in a large, lean bird at the end of rearing period which will certainly have a short production cycle, while the males will have their reproductive longevity compromised. On the other hand, birds completing the rearing period with a high fat deposition also tend to have shorter production cycles and to produce infertile eggs, resulting in low chick numbers.
There is no single magic formula to grow breeder flocks, since there are variations between regions, seasons and businesses. Despite these variations, careful, skilful management will help achieve the flock uniformity that provides the basis for good breeder results. It is, for instance, necessary to identify weaknesses in the daily farm routines and correct them to achieve consistently good overall performance.