By Rick Kleyn

As feed comprises the major input costs in broiler production, the nutritionist and the diets he or she formulates have a major impact on the ultimate profitability of any broiler operation. In essence, cost effective broiler production can only be achieved through accurate measurement of what has happened on the farm. Emmerson (2000) makes the point that in an integrated operation it is difficult to assess the effect of the impact of many production inputs in an effective manner. This limitation becomes further compounded when the production stream enters the processing plant since product from multiple flocks become mixed. As a result, it is impossible to link final product output to specific level of input, and consequently, it is impossible to develop a true optimal production solution.

Accepting that the "perfect" model of measurement of broiler production may be difficult to achieve in practice, we are still faced with a decision as to what to measure. Traditionally South African companies have measured performance characteristics. Emmerson (2000) makes the point that prior to 1995, at which time industry wide cost data became available, US broiler integrators also measured performance characteristics. At this point they moved to cost driven analysis of results. In the future all producers will have to measure performance in terms of returns rather than costs.

This paper will deal first with a discussion on the measurement of cost effective broiler production. It will then cover some of those aspects that reduce feed costs, improve performance or increase income. Rather than the technical mechanisms of feed formulation I will discuss some of considerations that need to be made in terms of the data to be used when formulating. In some instances I will simply question current practice rather than offer new solutions.

Evaluating broiler performance is complex. Over time we have moved from a simple measurement of bird weight, to weight for age, mortality, FCR and more recently to a Production Efficiency Factor (PEF). The advantage of using PEF is that all of the factors mentioned above are considered simultaneously and it gives us a reasonable idea of overall technical efficiency. For this reason it is often used as the basis for contract grower payments and the payment of management bonuses. The equation that we use to calculate PEF is as follows:

Liveability % x Mass (kg) x 100

The obvious shortcoming of using the PEF system is that it does not take any financial aspects into consideration. Just how poor the system was discovered when trying to evaluate the results of a trial conducted last year.

What is needed is a system that takes all of the performance parameters used in calculating PEF, together with some financial information. It must also take the major production economic principles into consideration as well. The principle that is of particular concern, is that where capacity is not limited then the objective should be to maximise the return per unit of production (per bird), but where capacity is limited then the objective must be to maximise the return per unit time. A calculation of the return per square meter of broiler housing per unit time (day) would achieve this goal as follows:

This model would make it possible to measure the return of a flock more accurately than is currently being done. In addition, by indexing a standard situation would be possible to compare flocks produced under different economic circumstances.

Whilst in the short term the age in days would not impact on the profitability, it would play a role if it allowed the cycle time to be changed.

Secondly, in this example I have used a live bird price. If the price were to be determined using the value of the final product minus the processing costs, this model would also need to take the cost benefit of slaughtering larger birds into consideration and if the situation demanded it, the value of the various components.

The results from a trial have been used to illustrate just how we can be mislead by using PEF. In the trial three energy levels were tested against one another, High (HE), Medium (ME) and Low (LE). The amino acid levels were kept much the same across all treatments as summarised below.

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It was of interest that the FCR changed by approximately 25 point per 0.1 MJ of dietary ME. This is in exact agreement with figures published in the literature Leeson & Summers (1998). The results of the trial are summarised in the Table 2.

If one were to only look at production parameters it can be seen there was a 4.2% difference in body weight between the HE and LE energy fed birds. It can also be seen that the HE diet outperformed the LE diets by about 16% in terms of PEF. When looking at costs a different picture emerges with the HE diet being only 2.1% cheaper than the LE diet. Interestingly the LE diet was a cheaper way of producing broiler meat than the ME diet. If one looks at the return per m² of chicken house it can be seen that the difference in return between the HE and LE diets is in the order of 8%.

In the real world it the value of the meat sold would be expected to increase as the birds got heavier or as the proportion of breast meat increased. Because this was a trial, all the birds were slaughtered at 42 days, so the impact of age was nullified. It will be noted that the mortality level measured during the trial were higher than one would expect.

This can be explained by the stress and subsequent mortality caused by weekly weighing. Under commercial circumstance we know that birds fed LE diets exhibit reduced mortality rates. If the mortality on the low energy diet had been 2% lower, then the return per m² per day would have been R 1.74, which is a little more than 2% less cost effective.

Another factor that would play an important role in commercial practice would be the stocking density that was kept constant during this trial.

The scenario above may well change if the cost of highly dense ingredients such as fishmeal, Acid Oil and Full Fat Soya were to increase, or if the cost of ingredients such as Bran and Sunflower Oilcake were to decrease.

From these data it is hoped that it has become clear that a more accurate measurement of not only the efficiency but also the costs and returns is required if we are to truly understand how cost effective we are as nutritionists.

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From the trial results presented above it is clear that deciding upon of the energy level of broiler diets is a major determinant of the profitability of a broiler operation. Broilers perform well over a wide range of energy levels as demonstrated by Leeson & Summers (1997).

Table 4: Performance and carcass characteristics of male broilers fed diets varying in level of energy (1 to 49 days of age)

In the light of this work and SPESFEED’s own research (Tables 1-3) it is clear that some form of economic analysis should be applied when selecting the energy level of the diet to be fed. As mentioned, US producers have become more cost oriented in the last 5 years. It is of interest to note that US producers have been reducing energy levels of their diets during this period so as to reduce their feed cost of kg of chicken produced. In the recently published Agristats (2000) it can clearly be seen how US integrators have been reducing the energy level of their diets over the last 5 years (Figure 1). It is of interest that the average bird weight has increased during this same period.

As the bird grows so its nutrient requirements change. In practice the energy level of the diets increases while the amino acid level decrease with age. Whilst age is a convenient way of expressing growth, it is very important to point out that this is a weight related relationship and not an age related relationship. As the genotypes that we feed achieve ever-higher weights at younger ages we need to adjust our practical feeding recommendations to meet these changes.

The manner in which the amino acid requirement declines with age is clearly illustrated by both Rhone-Poulenc, (1999) and Emmert (2000). Unfortunately as can be seen in Figure 2, days are used for reference rather than weight.

Simply using the amino acid specifications published by bodies such as the NRC (1994) or the companies that supply the birds is not an adequate approach. Dudly-Cash (2000) points out that three major developments have been made in amino acid nutrition during the last decade. These are the adoption or use of available amino acid values when formulating, the development of the Ideal Crude Protein approach when defining amino acid requirements and the development of phase feeding of broilers.

Logically we should meet the bird’s requirement for amino acids as closely as possible and to do this we need as many phases as possible. Oversupplying birds with expensive amino acids makes little or no sense and they can not be used for protein deposition and are in turn used for energy in a somewhat inefficient manner. Under supplying these same birds will lead to a reduction in performance.

In theory the more phases that are fed and the more evenly spaced these phases are, an increase in the efficiency of use of amino acids and possibly energy would be expected. Emmert & Warren (2000) have been able, using all three of the aspects of amino acid nutrition mentioned above, to illustrate this very clearly. These workers compared the NRC (1984) recommendation to three diets formulated using the equations similar to those shown in Figure 2. Digestible amino acid values were calculated from the total values. The specifications used in theses diets are summarised in Table 5 and the results in Table 6.

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As can be seen phase feeding had an impact on not only FCR (which was not significant), but also on Lysine utilisation. Although not shown, any reduction in Lysine usage would ultimately lead to a reduction in cost. Further experiments conducted on birds of different ages showed significantly improved performance in addition to improved amino acid utilisation.

It is often said that in making feed we do not always need to be right, merely consistently wrong. Feed consistency does impact on broiler performance as was clearly illustrated by Behnke and McCoy (1992). Three different mixing times, designed to represent poor, intermediate or adequate uniformity were used as the dietary treatments. A diet formulated to supply 80% of the NRC (1984) recommendation for Lysine, methionine, phosphorus and calcium was used. The results are summarised in the table.

Clearly feed that is not uniform may well cause a reduction in broiler efficiency. How then do nutritionists set about reducing variability in their broiler diets? Fawcett and Webster (1993) were able to demonstrate that variability in a diet is the product, rather than the sum of the variability, which occur at each stage of the production process. This variability would include ingredient variability, formulation errors, weighing errors and mixing errors. As nutritionists we must be able to control the quality of the ingredients that we use. Some commercial feed formulation packages, for example the Brill Corporation and Format International have routines that take account of the variability in feed ingredients, laboratories and scales.

Although beyond the scope of this paper, feed enzymes will impact on broiler nutrition in future. Phytaze enzymes are effective and cost effective although some problems still remain in terms of heat stability of these products. A new product has been launched which has higher heat stability and we are looking forward to its wider application. The Corn/Soya enzymes, which are mixtures of amylase, protease and zylenase would definitely appear to work under certain conditions and work is currently ongoing to determine what these conditions are.

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Achieving the correct cation-anion balance has become a goal for many broiler nutritionists yet it is surprising just how little data exists on the subject. Most commonly, electrolyte balance is described by the simple formula of Na+K-Cl expressed as mEq/kg of diet. In most situations it seems as though an overall dietary balance of 250 mEq/kg is optimum for normal physiological functions. In reality, electrolyte imbalance does not occur because the buffering systems in the body ensure the maintenance of near normal physiological pH. In extreme conditions the need for maintaining buffering capacity seems to adversely affect other physiological conditions (they have first call on the electrolytes), thereby producing or accentuating potentially debilitating conditions (Leeson, Diaz and Summer, 1995).

In young chickens an electrolyte imbalance can cause tibial dyschondroplasia. However this is not the problem that it was a few years ago and is likely to be less of a problem in the future as can be seen from figure 3 (McKay et al. 2000).

What constitutes a dietary cation-anion balance under normal conditions is hard to say. Martinez-Amezcua et al. (1998) were unable to show any effects on diets ranging from 180 to 300 mEq/kg, levels which probably cover the normal levels found in feed.

The major concern regarding the establishment of the correct Cation-Anion balance is that it can cost as much as R 40.00 per ton of feed. Based on the scant information available, particularly for the modern genotypes this practice must be seriously questioned.

From the above discussion it is clear that there is a difference between adequate and optimal broiler nutrition and feeding. Attention needs to be paid to the fine detail in order to maximize our returns as opposed to shooting for high PEF’s or low cost/kg of bird produced.

A consistent and logical approach must be used both nutritionally and in the feed that we produce. Carefully evaluate all the practices that are currently being applied in our diets, bearing in mind just how much the bird that we are feeding has changed.

Unfortunately, commercial pressures, which would include such items as the selling price of the opposition’s products, processor-producer contracts or producers who have set incorrect goals for themselves, often get in the way of doing what is correct.