As far as I can remember, this is the only thing Sonya and I disagree on. Good lab blocks are a complete balanced diet. I think the addition of supplimental food unbalances the diet. There are lab blocks especially designed for breeding colonies. They are higher in fat. For instance, Mazuri (www.Mazuri.com) Rodent Breeder 6F, 9F, and 11F are all 16% protien feeds. They differ in the fat content (6%, 9%, 11%). Strains that are able to produce very large litters, are able to utilize the extra calories. Otherwise it is not nessecary. To much protien can cause skin rashes in rats. Lab Diet (www.labdiet.com) produces two feeds that are 23% protien, 5001 with 4.5% fat and 5008 with 6.5% fat, so I assume 23% is still OK. BTW, I think Mazuri and Lab Diet are both owned by Purina.
That said, we both get great results. Which proves rats are very addaptable.
DeMak