Only a very limited number of factors can be considered including the raw ingredients and nutrition of the pet food. In most cases, formulators only consider key nutrients such as protein, calcium, phosphorus, energy, etc.
In addition, only small amounts of feed materials, such as grains and vitamin-mineral additives, should be used. In many cases, accuracy is largely ignored.
Currently, all consulting-qualified commercial companies and nutritionists use computer-based linear programming to design pet food formulations.
The value of linear programming is that it can handle various permutations of ingredient composition, nutrient requirements, and limiting factors in seconds. Numerous higher-level programs have preset NRC nutritional requirements for various animals and extensive raw nutrient content tables.
For those who can use a computer, most spreadsheet programs nowadays have the function of linear programming programs, which can design formulas at the lowest cost.
Some argue that "fixed-ingredient formulas" have nutritional advantages over "variable-ingredient formulas." They believe that switching raw materials between batches of products, taking into account cost, may lead to inconsistencies in pet food nutritional content and product performance. But the source of any ingredient can vary, and the nutrient content of ingredients such as meat, bone meal, soybean meal, or grains can vary widely from batch to batch.
Therefore, it is better to design pet food formulations with a fixed range of nutritional requirements rather than a fixed composition of ingredients. In the pet food industry, raw material replacement based on minimum cost is limited because pet food must be labeled with the proper name of each raw material, rather than the generic name "collective terms" in livestock feed. So be sure to take into account that the cost of reprinting the bag can offset the cost savings from the change in raw material composition.