Well-developed and evenly sized birds are the basis for good broiler breeder flock performance. This starts with proper rearing from the day of hatch. Critical points in the management of the flock must be taken seriously to achieving this goal.
By Jorge E. Amado, Technical Service Manager (Central America & The Caribbean), Aviagen Inc., USA
The day to day management of modern broiler breeders presents unique challenges. With advances in broiler feed efficiency and improving yields, attention to detail of parent stock becomes exponentially important. There are aspects of management that, if controlled during rearing (0-24 weeks of age), and under normal conditions of nutrition and health, will help achieve high and persistent productive and reproductive performance in broiler breeder flocks.
Knowledge of the physiological events that occur during development is very helpful to understand the growth profile. Thus, at the end of the brooding period (4 to 5 weeks old), the bird has reached about 50% of its skeletal size, and by 10-12 weeks of age over 90% of skeletal growth has been fulfilled (Figure 1).
Another very important point is to ensure a change in the direction of the growth profile of females around 15 weeks of age. From this age onwards, body weight gain increases, in order to build up reserves and achieve good body condition. Between 21 and 25 weeks of age, female growth rate rapidly increases (more so, than at any other time during the life of the flock) in preparation for the onset of lay. For males, this increase occurs between 19 and 24 weeks of age.
With the change in the growth profile at puberty, the females begin to "fill the breast", changing from "V" shape at 15 week to a "U" shape at 21 - 22 weeks. At least 80% of the females should exhibit this conformation at mating-up.
Grading and uniformity
A practical strategy to achieve higher uniformities from an early age is to increase the brooding area gradually from 3 days of age, with the complete removal of brooding rings by 5-7 days. This ensures that the birds have good access to feed and water during the first week of life, helping to promote good uniformity.
It is very important to support the growth of the birds by providing adequate feeder space according to the age. This is one of most common limitations in achieving better uniformities from early ages. It is also essential to ensure that uniformity and speed of feed distribution is optimum, independent of feeder type such as pan feeders, track feeders or hanging hoppers (Table 1). Feed should be distributed to all birds in less than 3 minutes, which can be aided by the use of additional feed hoppers.
At 28-35 days of age, the flock uniformity (CV%) should be calculated when the birds are weighed. At this time it may be necessary to separate the flock into 2 or 3 sub-populations, depending upon CV% (CV%<10 ="2" sub-populations, cv%>12 = 3 sub-populations). In the Latin American region, many companies with high productivities prefer to grade the flock (both sexes) into 5 or 6 sub-populations. The purpose of this is to narrow the weight range of each group. This effectively reduces competition, because of the homogeneity of the group (Figure 2). There may also be an additional advantage of being able to feed each sub-population more effectively according to its bodyweight profile.
Feed clean-up time should be monitored closely to ensure all birds receive adequate nutrient intake, while keeping competition to a minimum. In Latin America smaller pen sizes (approximately 1,000 females per pen) helps to reduce competition further, which may also aid population uniformity. It is not advised to re-grade the flock after 10-12 weeks of age, as their skeleton is already formed. Figure 3 describes the goals of uniformity expressed as percentage evenness of the population. The highlighted circles show the anticipated uniformity at 10, 15 and 20 weeks of age, which coincide with 90% skeletal growth at 10 weeks, change in direction of body weight gain at 15 weeks and again at 20 weeks.
Weekly and cumulative intake
Checking the development of abdominal fat (fat pad), in relation to bodyweight, in the females is also a good way to evaluate the feeding programme in rearing. A rule of thumb is to achieve an abdominal fat percentage of 1% at 20 weeks, 2% at 25 weeks, 3% at 30 weeks and 4% at 40 weeks of age. Adequate fat pad% will help to maintain persistent egg production.
It is recommended to confirm that the weekly intake requirements of protein and kilocalories per bird are being satisfied. When comparing the actual intake with the recommended theoretical levels, differences between the two may have a detrimental effect on the development of the growth profile. Similarly, the cumulative nutrient intake to 20 weeks of age should be at least 23,000 kilocalories and 1,200 grams of protein for females.
In order to ensure proper body weight gain of females between 15 to 24 weeks of age, and taking into consideration the administration of intramuscular vaccines between the 15-18 week period, greater weekly feed increases may be needed, with smaller increases being given between 21-24 weeks of age. This will help to maintain important bodyweight gains at this delicate stage of life. The development of reproductive tissues occurs after photo stimulation and failure to achieve adequate weight gain through puberty, is a common cause of the delayed onset of lay, poor initial egg size, reduced peak production, increased broodiness and loss of sexual synchronization between males and females.
Other areas to consider
Another key aspect to the development of birds is the implementation of an appropriate lighting programme during the rearing period. The day length should ideally be 8 hours in length with a light intensity of 10-20 lux. This day length should be achieved from as early as 10 days but no later than 21 days of age, and be maintained until at least 21 weeks of age in order to dissipate juvenile photo refractoriness. Increased day length (photo stimulation) should be given at 147-154 days of age, depending on the uniformity of the flock. Females and males should be mixed together from 161 days of age at a ratio of 9.5-10%. It is essential that only males and females of equal sexual maturity are mated-up. If immature males and females are mixed, this will lead to poor early fertility and reduced chick numbers.
Managing the modern broiler breeder is a unique challenge. Nothing is going to replace an objective and experienced farm manager to evaluate and constantly analyse the environment of the birds. However, with an understanding of the key areas discussed, it is possible to achieve and exceed performance goals. Attention to grading for uniformity, correct nutrient intake, proper lighting programmes and correct mating-up time all play an essential role in the success of a flock. Continued re-evaluation of rearing practices will lead to predictable and persistent broiler breeder production performance.