What does a 40% protein diet actually mean?
Many feeds boast high protein values. On one hand, protein requirements for fish are well researched and dictate how feeds are produced. On the other hand, protein is valuable. Feed companies know high protein diets can command a higher price-tag. This environment has created an interesting, and quite complicated, situation.
In nature, many fish eat other fish. This leads many people to assume that more protein is simply better. However, too much protein can be detrimental in terms of water quality, as extra protein will pass through fish and into the environment. We try to balance our formulations with respect to protein and energy—supplying protein in levels that will support maximum gain (protein accumulation) and utilizing better forms of energy (fats) for energetic considerations. This balance is called protein to energy ratios.
We will save going into specific detail about ingredients for a later time. For now, let’s just explore what “40% protein” on a tag actually means and the different approaches to achieving it.
Diets are comprised of a number of components. Each component supplies a unique set of nutritional compositional details. Many ingredients by themselves are higher than 40% protein, especially animal-based protein sources like fish and animal meal. Each of these protein sources vary in nutritional make-up…and price. Creating a feed for fish is a complex and multifaceted task, and formulations vary in terms of the ultimate result. While many people immediately think they want a feed that produces the fastest growth, others may want to balance growth with environmental impacts (like phosphorus discharge). Others may take into consideration fish health and well-being. Focusing on one particular outcome often comes at the expense of another, hence the difficulty in providing high quality fish feeds for such a diverse marketplace.
There are multiple grades and qualities of protein sources which we will dive more into at a later time, and there are multitudes of protein sources than can be utilized for the formulation and production of fish feeds. In the table below we are providing a simple, abbreviated chart of some of the more common ingredient sources used in fish food production and an approximate idea of their compositions.
| Animal Protein Sources | % Protein | % Fat | % Ash | % Fiber |
| Fish Meals | 50-80 | 8-15 | 10-25 | > 1.0 |
| Poultry Meals | 49-64 | 10-25 | 11-25 | > 1.3 |
| Blood Meals | 75-90 | 1-5 | 2-5 | <1.0 |
| Plant Protein Sources | ||||
| Soy Products | 38-75 | 1-20 | 1-50 | 3 – 30 |
| Corn Products | 5-75 | 1-10 | 1-10 | 1-10 |
| Wheat Products | 10-20 | 1-5 | 1-5 | 2-10 |
As many of you may notice, most of the ingredients have crude protein values higher than 40%. In order to achieve a final feed protein value lower than the individual protein source, the diet needs to be “diluted” down. If you have an ingredient with a high protein (ie. Fish meal), it needs to be mixed with something with a low protein (corn) in order to bring the average protein down. The higher the protein level of the specific ingredient, the more dilution is required. This presents a crucial decision to nutritionists: what protein source do you use and how do you fill out the rest of the formulation? These decisions will ultimately determine not only the cost of the feed, but also its performance with respect to fish growth and health, as well as its potential impacts on the environment.
To further complicate this, traditional floating fish feeds are extruded. Extrusion only works with starches and carbohydrates…which fish don’t generally eat. Fish and animal meals do not contain much starch content. Without starches the feed will fall apart and will not float. For example, a fish feed pellet comprised entirely of fish meal would overcook in an extruder and create an unstable and fast sinking pellet. Typically, plant products are utilized as starch sources. The long term effects of floating feeds high in starches and carbohydrates are poorly understood in fish and an area of active research and interest for us here at Optimal Fish Food.
Optimal Fish Food takes the approach of using high quality ingredients for not only the main protein source, but for ALL of the ingredients. Many of the conventional “dilution” type ingredients bring along sources of undesirable components. These are antinutritional factors like phytic acid and trypsin inhibitors, xanthophylls which can cause fillets to yellow, improperly balanced minerals which can facilitate disease, or low digestibility which can decrease water quality.
As indicated by the chart, there are a wide variety of protein sources and grades to choose from. We’ll talk more about how we choose from that list and how we go about evaluating our ingredient choices in our next installment.
