Considering switching to rats, but have a question!

[Quantum Constrictors]

Couldn't just be from rats being bigger overall (i.e., feeding more food)?

Not really you could have a rat and a mouse the exact same weight BUT the nutritional value IS different.

For the sake of everybody :

Nutritional Value of Mice

Energy
-Dry Mass -Protein -Fat -Ash -kcal/g
Pinkies -19.1% -64.2% -17% - 9.7% -4.87
Young Mice -18.2% -44.2% -30.1% -8.5% -6.65
Adult Mice -32.7% -55.8% -23.6% -11.8% -5.25


Nutritional Value of Rats

Energy
-Dry Mass -Protein -Fat -Ash -kcal/g
Rat Pups -20.8% -57.9% -23.7% -12.2% -5.3
Young Rats -30% -56.1% -27.5% -14.8% -5.55
Adult Rats -33.9% -61.8% -32.6% -9.8% -6.37

Chart taken from : http://www.leedspetshops.co.uk/index...age=page&id=69