This is a guide to common gerbil foods found at a store served as is, directly from the bag. Most diets are not designed for gerbils. Gerbils get lumped together with Hamsters, Rats or Mice. When evaluating food you should look at the top ingredients. Corn, Milo, Millet, Timothy Hay (or alfalfa) Pellets, and Safflower Seeds are fillers. Milo or Sorghum and Safflower Seeds are generally inedible. The higher these ingredients are in the list, the less suited the diet is for gerbils. Keep in mind that manufacturers often change their recipes.
Generally speaking gerbils need 12-16% protein and 5-8% fat. However, gerbils have different dietary needs through out there lives. Young gerbils are still growing and need the extra nutrition to support their growth and activity. . Senior gerbils over 2.5 years often slow down and live fairly sedentary lives their nutritional requirements are much lower. Over the years I have noticed there is a strong aversion to feeding gerbils fatty foods like sunflower seeds, peanuts, and other seeds and nuts. Most commercial diets do not provide enough fat for an adult gerbil never mind a pup. Please do not remove seeds, nuts or any other ingredient from a commercial diet blend to try and make it "healthier". I offer plain, store brand cheerios (with 0g sugar) to my gerbil.
Gerbils under six months old and breeding females need higher protein 15-16% and higher fat 7-9%.
Adult Gerbils need 12%-14% protein and 6-8% fat.
Senior gerbils over 2.5 years need 10-12% protein and 4-6% fat.
When I decide which blends are Great, Good, Poor or Very Poor I am looking at protein, fat, and ingredients. Protein should be between 10-16%, ideally around 13%. Fat should be between 5-8%. However, its the ingredients that I am most interested in. If corn, timothy hay, milo or sorghum is in the top 3 ingredients the diet is going to get a poor rating. If corn is in the top 5 ingredients it may get a poor rating, depending on the fat and protein percentages. I like to see barley, oats, and wheat as the first ingredients. I also like to see a variety of foods in the diet.
There is one diet in here The Power of 5 Hamster and Gerbil Diet, that I really want to like. Its the only pelleted diet I would recommend other than rat blocks. However the diet is super high in protein. My recommendation for using that particular bag of food (or any other rat lab block) is to buy a different type of gerbil food and mix the two together.