The Quality of Protein Sources in Aquatic Turtle Diets (useable vs. non-useable Proteins)

So, to start, a little biology 101. Sorry – No way around this! But Proteins are a very important factor in providing good nutrition, so it’s worth the time to review.

First – Dietary Protein is extremely important in a food source since it is responsible for maintaining the body’s working parts. Body tissue, whether its muscle, skin, or blood is made up primarily of proteins. If your turtle cannot take in the proper amount of protein, in a quantity and form that addresses its requirements, it will not have the resources needed to maintain growth, repair of the body, or maintain general good health. So, understanding the use of dietary proteins is extremely important in choosing a good diet for your turtles.

So here are some of the basics: Proteins are made up of Amino Acids, that is why amino acids are always referred to as the “building blocks” of protein. Once an animal ingests a protein source, it’s body (through the use of various enzymes) disassembles the proteins into their base form- the amino acids. That is the basic process of assimilating protein into the body. Once the body has these “assorted” amino acids available, it can now reassemble them into whatever it needs to maintain the body (muscle, skin, etc). Really, that’s the whole story in a nutshell, and although you could go into depth on this subject for pages and pages, that’s the basic process in a paragraph. But regardless of the simplification, you can still get a good idea of how important proteins and their amino acid profiles are by starting with this basic understanding.

But here is where it gets interesting and a bit more involved; different proteins are made up of different amino acids. There are 22 different amino acids in total and they vary in their combinations depending on the protein source. Not all proteins have a good “assortment” of amino acids for an animal’s body to use, so some protein sources with a better (or more balanced) assortment of amino acids are considered a “higher-quality” protein then others. This is where you get into the term “useable” protein, it refers to how much of the total ingested proteins can actually be re-used by the body (based on its amino acid profile).

There is a standard of measurement used, called the Net Protein Utilization or NPU, that rates the quality of a protein source. The NPU grades the usability of a protein based on its amino acid profile and its “useability” for an animal’s body to rebuild what it needs. On the NPU scale of 1-100% for example: an egg has a NPU of 98%, making it one of the most “complete” proteins available, fish meal rates an impressive NPU of 82%, and other meat sources range between 68%-78%. Protein sourced from Plant materials come in much lower on the NPU scale, since most plant proteins have the least desirable (limiting) amino acid assortment. Soy has the most useable plant protein with a NPU of 48-61%, while corn comes in at a disappointing NPU of 20-26%.

As you can see by the numbers, a high-quality animal protein source will have a more useable amino acid profile then do proteins from plant sources. Aquatic Turtle Diets with a high fish meal content (or other meats) for example, will provide a better amino acid profile then diets built on soy, wheat or corn. Many plant protein sources can be a very useful “addition” to a diet for aquatic turtles, but the diets primary protein source should come from animal protein.

This is the same battle the major dog food companies are fighting right now, many brands making the jump from poorly formulated corn-based kibbles, to foods which use more animal protein sources instead (chicken, lamb, beef, etc). The better Aquatic Turtle Diets are following this trend toward better NPU performance. This is why you really have to look closely at the ingredient listing on your Aquatic Turtle food, If the diet is built on corn, wheat, soy, or other low NPU ingredients, PASS on it and look for one with higher quality animal protein components. Protein is a major consideration in any Diet for Aquatic Turtles and care should be given to provide a diet that includes high quality animal protein ingredients.