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Background

While addressing growth of the broiler chickens, farmers may usually target market weight as per market requirement. Usually in all-in-all-out production systems, farmers have to control managemental aspects efficiently. Breed, nutrition, health status and managemental practice are the main determinants of profitability.



Growth of broiler chickens

Ideally the weight in a broilers could be presented sin the form of normal curve (Figure 1). However variations in growth rate are possible and may lead to altered shape of the curve. In most of the case, the later example means that broiler weights are inferior to the average weight of the flock.



Adjusting nutrient concentrations

Growth modeling programs may be applied to assess the effect of nutritional modulations. It would be advisable to determine the nutrient-growth interactions of broilers on the basis of geographical location. Several models could be considered for optimizing profitability as shown in figure 2 and 3. Figure 2 illustrates the effect of feed intake on profit per bird while figure 3 illustrates effect on returns with increasing body weight and feed intake. It would be interesting to consider interaction of both curves in different temperatures.



Broiler body weight variations

If the birds are uniform, greater proportion of the flock reach the specified target weight range in a shorter time period. Alternatively, higher percentage of birds reach the premium priced weight targets as per specifications. Knowledge of uniformity within a house may help in optimizing nutritional formulations during condition of environmental stress. One must assume that birds would show variations as a response to interaction between feed intake, temperature and location.

Example - The greater the variation in weight of a broiler in a flock, the larger will be the standard deviation. In a normal distribution, one standard deviation about the mean will include 68.3 percent of the birds in the total group. Two standard deviations will take in 95.45 percent of the birds, and three standard deviations will include 99.73 percent.



Feed conversion

Much of the variation (85 to 90%) among broilers in feed consumption and feed efficiency occurs due to age and body weight differences. Increased body weight is associated with increased feed consumption and reduced feed efficiency. As birds increase in body weight, maintenance energy requirement is increased. Thus less energy is used for the muscle growth. In the 7d old bird, about 80% of feed is directed to growth and only 20% is needed to maintain the small body size. As the age advances the ratio is altered and feed efficiency is reduced.



Broiler chickens-males vs. females

Usually farmers would receive equal proportion of males and females in the flock. Males and female broiler chickens differ in their growth pattern. After about 30d age, females broilers tend to deposit proportionately more fat in the carcass. It is well known that fat production is an energy intensive process than protein production and it would take approximately 9 times more energy for fat deposition. For production of muscle, energy requirement would be even more less as it is only 20% protein reminder being water. All these factors contribute to differences in feed conversion between males and females. Thus females may be less economical at advanced ages. These factors should be considered while marketing birds at different ages.



Improving flock health

Genetic selection for fast growing broiler chickens may lead to improvement of about 2 points in feed conversion and 0.1% evisceration rate. Modern birds are hyperphagic. Therefore, lack of feed could cause problems in enteric disease control strategy. Presence of disease would lead to growth reduction. Presence of disease would also lead to higher feed conversion. If growth variation within a flock is too high, flock health should be the first target for attention.

A related practice would be to minimize the impact of existing disease outbreak through careful attention to nutrition, ventilation, health management, and the removal of social and environmental stressors to the greatest extent possible. Several nutritional additives are available in the market (Table 1).Access to feed and water is also important. Restricted access to the feeder or to the drinker will adversely affect performance resulting in increased variability.

Table 1- Generic example of available nutritional supplements in the market

Figure1. Generic distribution of broiler chicken body weights





Figure 2. Illustration of effect of feed intake on profit per bird





Figure 3.  Diminishing returns function for body weight as a function of feed intake

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