Hamsters and guinea pigs belong to the same order of rodents. Although they share many common “touch points”, many owners and breeders of these animal species agree that food should be different.
Looking at the natural features, as well as their feeding regime (that they are in the wild), there are obvious differences in the feeding of these two animal species. Thus, in the wild, guinea pigs feed primarily on grass and hay (herbivores). It is hay that ensures the development and normal function of the guinea pig chewing muscles and ensures normal tooth wear. Unlike guinea pigs, hamsters are collectors of primary seeds and cereals. However, as their diet can sometimes have some small insect, we can consider them omnivorous.
According to the needs of the organism, there is an important difference between the two animal species, which is evident in the need for the vitamin C. Namely, the guinea pig organism is not able to create by its own mechanisms sufficient (necessary) amounts of this vitamin. Therefore, their diet must be supplemented with vitamin supplementation which isn’t necessary for hamsters. Also Guinea Pig Mix/pellets typically have more protein in, which isn’t as high in Hamster mixes.
The hamster food you should look for includes 12-24% protein and 3-6% fat. The only time you need to really raise the amount of protein you give to a hamster is when its a baby, a pregnant mother, a nursing mom, or under 8 months old. If you continuously feed you hamster a lot of protein (as much as you feed it when its a baby, a pregnant mother, a nursing mom, or under 8 months old) it can cause kidney and liver issues.
Also, while any food can become impacted in your hamster’s cheek pouches, you can be more confident that foods specifically designed for hamsters will have less chance of damaging your hamster’s cheeks.
Because of all of the above, the best advice is to not use guinea food mixtures. It probably wouldn’t harm them, but it just does not provide essential nutrients hamsters need.
So, keep to food mixtures made exclusively for hamsters. You can give them some guinea food once in a while, but never include it on a regular menu.