by Rick Kleyn, SPESFEED (Pty) Ltd

As our poultry production systems become more intensive and more competitive, we continually need to evaluate what we are currently doing and explore new opportunities. The use of the feed ingredients that we use is and will always be important to the nutritionist and the use of alternative feed ingredients represents what is possibly the greatest opportunity for nutritionists and poultry producers.  It is true however that any feed is only as good as the ingredients that are used in its manufacture.

Before any decision with regards an ingredient can be made, it is essential that the nutritionist knows everything there is to know about it.  This means that the nutrient content should be known; that the physical structure or form of the ingredient is correct; that the processing has been such that the nutrient bio-availability has not been negatively impacted; and that the biological quality of the ingredient in terms of any possible pathogen or toxin contamination can be assured.

Once satisfied that you have complete knowledge of an ingredient, the economic value of the ingredient can be determined. Traditionally, there are three aspects that determine the value of an ingredient, these being; the price and nutrient content of the ingredient itself; the price and availability of the other ingredients; and lastly the diet in which it is to be used.  By making use of the ranging/sensitivity features of a standard feed formulation program it is easy to determine the value of any ingredient in any specific product.  By extension, Multi-Mix® (Format International) technology gives the nutritionist the ability to determine the value of an ingredient across a whole range of products.  

Evaluating ingredients using standard feed formulation programs does have a major shortcoming.  LP generates a ‘least cost’ diet for a certain pre-determined feed specification.  It does not look at the overall profitability of the production process.  Opportunity may well be lost if the nutritionist ignores bird response to nutrients, in particular nutrient density, and it is this aspect that needs to be added to our methodology of evaluating an ingredient.

The determination of the energy level of poultry diets is perhaps the most important decision that has to be made by the nutritionist. Energy contributes approximately 60 to 70% of the cost of a broiler diet, making the selection of an energy level that will maximise profit all-important. It is widely accepted that nutrient requirements should be expressed in terms of grams of nutrient per unit of energy contained in the diet. By deriving functions of broiler response to energy density, it is possible to determine the optimum energy level of a diet.  Saleh et al. (2004) and Guevara (2004) have both studied the effects of nutrient density on the modern broiler.  A simple set of polynomial models was fitted to the data of Saleh et al. (2004) (figure 1).

Figure 1: Response in body weight gain and FCR in male broilers to incremental levels of nutrient density, after Saleh et al. (2004)

By making use of a standard feed formulation program, the ideal amino acid profile as published by Lemme et al., (2004), standard ingredient costs and an estimated value for a live broiler, it is possible to calculate the return at the different energy densities.  This can be seen in the “Standard” line in (figure 2).   

Whilst this data is useful, it was determined using very low bird stocking densities (10 birds/m²).  The work of Berri et al, (2004) demonstrates clearly that at higher stocking densities birds respond to nutrients, total lysine in this case, in a different manner.    The consequences of this are that often experimental data may not apply to commercial conditions. Where stocking densities are higher the expected growth on lower density diets may well be over-estimated.

It is of interest that Saleh et al. (2004) reported that there was no increase in mortality or leg disorders when feeding high-density diets. Abdominal fat was not adversely affected by increasing nutrient density when protein was maintained in ratio to energy.  Breast meat yield and percentage remained constant as the nutrient density changed.

By making use of the data published by Saleh et al. (2004) and the same iterative methodology as described above, it is possible to illustrate exactly how ingredient availability or price will interact with nutrient density.  To this end, it was assumed that a) relatively cheap Sunflower Meal and b) relatively cheap Full Fat Soya become available.   The results of this evaluation (Figure 2) illustrate that should sunflower be available, it may well pay the nutritionist to reduce nutrient densities.  On the other hand, should FFS become freely available, it will pay to use more dense diets. 

Figure 2:  The return per broiler at incremental nutrient densities, for standard diets (- -), diets including cheap sunflower meal, (_ _ _) and diets including cheap FFS (___), using the data of Saleh et al., 2004.  

The take home message from this short article is simple.  Remember to take bird performance and financial return into consideration when evaluating alternative ingredients.  If you assume a fixed feed specification you may well not be feeding diets of optimum nutrient density.

A complete list of references is available from the author.