As we all know, what we eat can drastically affect our health. For example, too many carbohydrates can result in obesity, too much sugar can cause diabetes, omega-3 fatty acids can reduce the risk of heart disease, avocados apparently cure everything, and too many beans make us fart. The connection between diet and health is also true for laboratory animals. The animals’ diet will obviously affect study outcomes if it is not controlled. In order to control dietary variables the lab animal community has established standardized diets for its animal models… except for zebrafish.
That’s right, there is no standardized diet for zebrafish. How could this have happened? Well zebrafish are like that new guy at school who is kind of weird but in a cool way so everybody wants to hang out with him. Zebrafish are relatively new to the laboratory animal scene and their popularity has increased dramatically in the last 15 years, which has resulted in certain husbandry aspects being left in the dust. One of which is the nutritional requirements of zebrafish. After all, how can we make a standardized diet without knowing what they require? As we all know, page 85 of the Guide for the Care and Use of Laboratory Animals states: “Care should be taken to feed a complete diet to avoid nutritional deficiencies”.
When I say nutrition I’m talking about the same things you see on the side of your cereal box in the morning: calories (energy), fat (lipids), proteins and amino acids, carbohydrates, vitamins, and minerals. Each of these nutrients is required to some degree for each individual species. So let’s get down to the nitty-gritty, what do we know about zebrafish nutrition, and what don’t we know?
- Energy. We do know that energy can come from proteins, lipids or carbohydrates. We don’t know quantitatively how much energy is required by zebrafish.
- Lipids. We do know that lipids provide essential fatty acids (EFA), and that deficiencies can result in reduced growth and embryo production. We don’t know quantitatively how much EFA they require.
- Proteins and Amino Acids. We do know that fish require 10 essential amino acids (Arg, His, Iso, Leu, Lys, Met, Phe, Thr, Trp, and Val), and a deficiency in any one of these can result in reduced growth. We do not know the requirements of nine of those amino acids. A manuscript submitted by myself is currently under review in which the lysine requirement of zebrafish has been determined… (SPOILER ALERT!) it’s 2.2% of the diet.
- Carbohydrates. We do know that carbs are not a major source of energy for most fish species. However all fish diets contain some carbohydrates and thus determining the digestibility of the carbohydrate sources is needed.
- Vitamins. We do know that vitamin deficiencies can lead to abnormal swimming, deformities, edema, lethargy, altered immune response, etc. We don’t know quantitatively how much of each vitamin is required.
- Minerals. We do know that several minerals are required, however some of them can be absorbed from the environment. Deficiencies in minerals can result in reduced growth, skeletal deformities, anemia, etc. We don’t know quantitatively how much of each mineral is required.
It is obvious that nutritional information is lacking for zebrafish, so what is being done about it? Last year the Zebrafish Husbandry Association (ZHA) established a working-group to tackle this issue. It became obvious that extensive funding for zebrafish nutrition research is needed and that the ultimate source would have to be from NIH. In April 2016 a contingent of interested parties gathered before the Experimental Biology Meeting to discuss how to proceed. Representatives from NIH, ZHA, USDA, American Society of Nutrition, as well as several public and private parties determined that a much larger workshop should be held before next year’s Experimental Biology Meeting. This meeting is to include many nutrition experts from other animal models, the American Physiological Society, and several research diet companies.
The establishment of a standardized diet is far from complete. However it appears that the movement is gaining momentum. Expanding awareness within the laboratory animal community is vital and the zebrafish community appreciates your Biosupport.
How to cite:
Tye, Marc. Zebrafish Nutrition: What We Know and Don’t Know. Eureka blog. September 13, 2016. Available: http://eureka.criver.com/zebrafish-nutrition-what-we-know-and-dont-know/