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I have a question regarding feeding high fat diets to mice in our unit. We have used a diet called 'RM AFE 45% FAT SY(P)' for the past number of years for several diabetic projects and have had no issue with animals gaining weight, however recently we have problem them with maintaining weight. The manufacturer has confirmed that there has been no change in the formulation of the diet and there are no environmental changes in the unit ,if anything the environment is quieter as there is less going on due to Covid-19. I would be interested in any thoughts.
Here are my thoughts on points I would consider in the first instance knowing that mice do enjoy high fat diet:
How do you store the diet? Are the diets frozen and only small amounts are taken out for feeding?
I assume the diets are all in date and food intakes of the batches of mice were checked so that a palatability issue can be excluded.
How often do you top up the hoppers and how long is the diet left in the hoppers? Is it measured out or ad libitum?
Which mice strains are you using? For example I have seen C57Bl6 batches as well as individual mice that literately did not put weight on despite being fed a high fat diet.
Do you see a difference between males/females?
How old are they when started on the diets? Do they initially put weight on and then only maintain? Do they actively lose weight?
Are all mice affected or only a few? Do you have any mice grinding the diet rather than eating it?