Best Pellets for FED 3

[jv...@scarletmail.rutgers.edu]

Hello FED Community!

What are the best pellets to use for the FED 3  (i.e. they do not crumble or generate powder easily)? Does anyone know of a good manufacturer who can produce those pellets of the correct size? Any help is much appreciated.

- Jay Phansalkar

[Lex Kravitz]

Hey Jay,

I have a page on the Wiki about this.  We use sucrose pellets from TestDiet which are the easiest to dispense if you are OK with using sucrose pellets in your experiments.  We also use grain pellets from TestDiet, which are more crumbly than sucrose but are a complete nutrition replacement which we use for multiday feeding studies.  Hope this helps! -Lex

[Qichen Fan]

Hi Lex,

I'm considering switching from grain pellets to sucrose pellets and I'm trying to figure out how that might impact my experiment. My intuition is that mice would be more motivated to consume the sucrose pellets, so they might learn operant tasks better if I use those as rewards. Do you know if there's any clear evidence that mice prefer sucrose over grain pellets? Thanks!

Will

[Lex Kravitz]

Hi Will!  I'm not sure if sucrose pellets are more reinforcing than grain pellets.  Mice consume similar numbers of each type in our operant tasks and they prefer both types of pellets to their laboratory chow.  So I don't have a great answer on which pellet is better as we don't often give them access to both types concurrently. 

It seems like something we should figure out though, does anyone on here want to crowd source an experiment on this?????  I can mail people some grain and sucrose pellets, if anyone wants to do a simple preference test and share results please email me!

[Victor Cazares]

Hi all,

We did this experiment, you can read it here: https://www.sciencedirect.com/science/article/pii/S2352289520300527

In brief, mice prefer grain pellets until they are habituated to sugar pellets (then they prefer sugar). Though, there are some strain differences. We also use this preference to do an "effortful pellet preference". That is, they could have their non -preferred pellet on free feed vs. Preferred on PR. 

Anyway, check it out and let me know if you have questions.

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[Qichen Fan]

Hi Lex and Victor

Thanks for your answer! Victor, you used chocolate pellets in your experiment. Do you think sucrose would have similar effects?

Will

[Victor Cazares]

Hi Will, 

Sorry, just to clarify - they are sucrose pellets but you can get them flavored. We opted for the chocolate version because the 129S1 strain is less motivated by pure sucrose flavoring. Other than the flavoring the composition of the sucrose pellets is the same, here is the formula.

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[Qichen Fan]

Thanks for your clarification!

[Christine Liu]

I just came across this recent paper that compares different type of pellets (balanced-diet pellets, sucrose pellets of different flavors) in CD1 and C57 mouse behavior. In summary, both strains consume more balanced-diet pellets in low-effort tasks, but will work harder to earn sucrose pellets.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10497155/

Might be interesting to try different types of pellets, or even do a preliminary direct preference test with two FED boxes containing different pellets to see what works best for the tasks and mice in your experiments. Now I'm curious about the neural mechanisms that mediate the difference in motivation for sucrose vs balanced-diet pellets!!

[Victor Cazares]

Hi all,

We compared C57BL6/J and 129S1/SvImj mice for their pellet preference (grain vs. chocolate flavored sweetened pellets). We also compared pellet consumption of the preferred pellet on PR vs. non-preferred FR1 (see here, Figure 3). Both strains displayed neophobia to the pellets, so habituation should be carried out prior to the preference test. Overall the 129S1 are “less picky” eaters haha. We also mostly run our FED trials with ad-lib food, surprisingly we find pretty good responding even if you have grain chow present while the FED dispenses grain pellets .

Happy to participate in any multi-lab experiment!

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[Lex Kravitz]

We also often train with regular colony food in the cage - we find that for simple tasks (free feeding, FR1) they prefer the little gain pellets to the colony chow so it's fine to train with colony chow in the cage.  For more demanding tasks (PR or bandit tasks) they will start to eat the colony chow so we remove the colony chow for that.

I'd also be happy to participate in a multi-lab experiment on this!