Monday, March 10, 2008

FACTS on Least-Cost Animal Feed Formulation


The practice of ingredient interchange, known as "least-cost formulation," is widely practiced within the commercial feed industry. When the cost of one ingredient increases, a lower cost ingredient may be used as a substitute in order to produce a lower cost feed, providing the customer with the most economical feed for animal production. It is widely know, however, that laboratory feeds are fed to animals raised for breeding and research, not for animals used to produce food such as meat, milk and eggs.

Least-cost feed formulation is combining many feed ingredients in a certain proportion to provide the target animal with a balanced nutritional feed at the least possible cost. Though least-cost formulation is a mathematical solution based on linear programming, it requires the professional knowledge of animal nutritionists who take into consideration the nutrient requirements of the target animal and its capability to digest and assimilate nutrients from various available ingredients.


Ration (or feed) formulation does not merely involve mathematical calculations to meet the requirement of the animals, since the result of the calculation may turn out to be impractical and not ideal for feeding animals. An experienced animal nutritionist, therefore, needs to evaluate the feed formulation before it can be given to the animals. Factors to be considered in making good feed formulations are:

1. Acceptability to the animal. The ration being formulated has to be palatable enough to stimulate intake by the animal. Feed refused by the animal is worthless, since feed has to be coiisui-ned and utilized by anii-nals to serve its purpose. Moreover, feeds left too long in the feed trough may spoil and become unfit for the animal.

2. Digestibility. The nutrients in the feed have to be digested and released into the gastrointestinal tract to be utilized by the animal. Rations with high fiber content cannot be tolerated by poultry and swine.

3. Cost. The requirement of the animal can be met throu-h several combinations of feed ingredients. However, when the cost of these ingredients are considered, there can only be one least-cost formulation. The least-cost ration should ensure that tile requirements of the animal are met and the desired objectives are achieved.

4. Presence of anti-nutritional factors and toxins. The presence of anti-nutritional factors in the feed, such as anti-trypsin factor in soybean meal, affects the digestion of some nutrients by making them unavailable to the animal. Some feed ingredients may also contain toxic substances, which may be detrimental to the animal when given in excessive amounts. The inclusion of these feed ingredients should therefore be limited or eliminated froi-n the formulation.

Other factors that should be considered in feed formulation are texture, moisture and the processing the feed has to undergo.


There are several methods in formulating rations. All of them have the same objectives of providing the required balanced nutrients at the least possible cost. The five methods are as follows:

1. Square Method. This is relatively simple and easy to follow. It satisfies only one nutrient requirement and uses only two feed ingredients. Another limitation is that the level of nutrient being computed should be intermediate between the nutrient concentration of the two feed ingredients being used.

2. Simultaneous Equation Method. This is an alternative method for the square method usincy a simple algebraic equation. Here, a particular nutrient requirement is satisfied using a combination of two feed ingredients.

3. Two-by-two Matrix Method. This method solves two nutrient requirements using two different feed ingredients. A 2 x 2 matrix is set and a series of equations are done to come Lip with the solution to the problem.

4. Trial-and-error Method. This is the most popular method of formulating rations for swine and poultry. As the name implies, the formulation is manipulated until the nutrient requirements of the animal are met. This method makes possible the fori-nulation of a ration that meets all the nutrient requirements of the animal.

5. Linear Programming (LP). This is a method of determining the least-cost combination of ingredients using a series of mathematical equations. There are many possible solutions to each series of equations, but when the factor of cost is applied, there can only be one least cost combination.

An electronic computer is capable of making thousands of calculations in a very short time. However, the machine is incapable of correcting errors resulting from incorrect data and errors in setting up of the program. Therefore, the resultant rations obtained from linear programming will be no better than the information and values which are entered into the programming.


Before using the LP approach to ration formulation, the user should be familiar with the LP program or software package to be used. There are certain informations and data entered into the computer and are generally created in steps as follows:

I . Available feed ingredients. It is necessary that all the available ingredients are listed alon- with the unit cost, as long as the number does not exceed some practical figure which the machine is capable of handling.

2. Nutrient composition of feed ingredients. Tables of feed composition using average or typical values may be used but chemical analysis of a representative sample should be used if available.

3. Ration specifications. This generally represents the nutrient requirements and ingredient limits. In each case, the formulator specifies either a lower limit and/or an upper limit for each item.

4. After providing all the necessary information, the computer produces a formula that will rneetthedesiredspecificationsatthelowestpossiblecost. However,theformulashouldbe feasible, both from a mathematical standpoint and from a nutritional standpoint. The feedstuff mixture should be acceptable to the animals for which it is intended.

No comments: