How often do you change the diet in your animal’s cages?
In most animal facilities, the frequency is probably once per week, along with a new cage, bedding and water. Depending on the diet being fed, however, there may be reasons to provide new diet more often.
One example is when feeding very high fat diets, such as D12492. From feedback we’ve received from some customers, food intake and body weight gain is often more stable when the diet is changed twice per week. In other words, some D12492 users find that if they change the food only once per week, the animals consume fewer grams of food and their body weight gain slows by the end of that week, picking back up when cages are changed and new food is offered. The exact reason for this is not known and researchers have speculated that the food becomes less palatable due to fat oxidation and/or the possible growth of bacteria on the diet due to the interaction of the animal with the pellets. To our knowledge, no one has tested either of these theories. I should also emphasize that many D12492 users only change the diet once per week and are quite satisfied with the data they are generating. The only way for you to know is to try it both ways in your facility and see if there is a difference.
Researchers should consider changing the diet at least twice per week for diets high in polyunsaturated fats, such as menhaden (fish) oil. The long chain, polyunsaturated fatty acids in menhaden oil are more susceptible to oxidation, owing to the multiple double bonds present. While suppliers of menhaden oil often mix an antioxidant into the oil (for example, tBHQ), it is still prudent to treat diets high in polyunsaturated fats differently than other diets. This would include storing the diet frozen and away from light, and changing the diet often in the cage.
There are likely other instances where you should change the diet more frequently than once per week and if you have any cases of this, please let us know. If more frequent diet changes are reducing your data variability by way of stabilizing food intake and/or body weight, then by all means do so. If things work just as well with a weekly food change, go with it. As we have told customers over the years, do what works best for you.