. Mads Kjolby, MD, PhD, Assistant Professor, Aa
Webinar Q&A Report: Monitoring Food Intake, Water Intake and Ingestive Behavior in Group-Housed Rodents
Q: What is the maximum number of animals that one can put in a cage to study group-housed Ingestive behaviour? RENÉ: The system itself has no limits regarding the number of animals it can track as part of a group. However, there is likely local legislation or internal policy that sets guidelines for how much space animals require within a cage. The default cage used is the Tecniplast 1500U Eurostandard Type IV S (480 x 375 x 210 mm) with a floor area of 1500 cm2 or 232.5 in2. This is used for both rats and mice. It is also important to note that the strain of animal will also set certain limits. For example, the male C57 black 6 mouse is known to be aggressive. Based on customer experience with this particular strain of mouse, the recommendation is to house no more than 4 siblings per cage. Female mice could be as many as 8. For rats, cage space typically sets the limit. Q: How does one know that the system is working properly once set up? What should users be looking for to ensure proper operation? RENÉ: The HM-2 system generates a variety of health and operational quality recordings that is intended to document the quality of a specific session. That is:
Hardware Diagnostics – a guided check of all sensors and detectors with results logged in the system. This test is typically done every 3 months.
Online system condition – The status of each HM-2 station is shown as a pictogram in the cockpit view. 7 pictograms of system conditions are easily spotted in the list of base stations in this cockpit chart overview.
Meal and drink size limits – serves to detect meal registrations that are highly improbable. The configurable values may be used as a filter in the extraction of data.
Chamber event list – Data about when detectors are active and when the channels are blocked, due to service or husbandry.
Feed and Drink Ratio diversion – Let the system tell you when an animal drinks more than it usually do or maybe eats less.
Unidentified intake is registered on a missing reading of RFID tag or if the tag is not accepted. Intake is registered on cage level (UI) and as separate columns in graph. Reason for UI: Misplaced animal, lost RFID tag.
Body weight in - or decrease is detected if defined limits are exceeded.
All information is recorded in the database and may be filtered to become your standard quality report accompanying your session results Q: How can we be sure that individual water and food intake is accurate given spillage and evaporation? RENÉ: As long as there are no animals in the channel the load cell, weighing water and feed intake, is reset continuously to “zero” – an automatic tare function. This ensures that evaporation is removed before each meal. Q: Do you have a system for rats and mice? What is the difference between the two? RENÉ: The HM-2 system can be equipped with feed kits either rats or mice. The difference of these kits are the size of the channels and the cage entrance to the channels. The switch from one kit to the other is done in 2-3 minutes per station. Q: Could you add a video recording to each cage for social interaction studies? RENÉ: We have the possibility to connect a webcam on the system. It is possible to control the webcam’s start/stop function by specific events of the HM-2 station. At this point we offer this as a custom solution. There is no phenotyping or tracking software available from MBRose. Q: Can we measure activity of individual animals within the cage? RENÉ: Currently, there is not option to measure activity of individuals within the cage. The PIR sensor only detects general activity on the cage level and not per individual. Q: How big are the cages compared to other cages, e.g. IVC cages? RENÉ: Most standard cages can be fitted to the station. The most common is the Tecniplast 1500U Eurostandard Type IV S (480 x 375 x 210 mm) with a floor area of 1500 cm2 or 232.5 in2. This can be used for both rats and mice. The largest cage we have used is the Tecniplast 1354G with floor space of 1820 cm2 or 282.1 in2.
Q: To increase # of animals per cage is it just a RENÉer of adding more eating/drinking channels? RENÉ: The HM-2 system has 2 channels (food and/or water) that detects all microchipped animals that are feeding and/or drinking. However, the system does not have a limit on the number of animals it can use. Please refer to question #1 for more information. Q: Can you place more than two bottles or food? Or is two the maximum number of channels? RENÉ: Yes, the maximum number of channels is two. If you are studying feed preference you can have feed in the two channels and water in the lid of the cage. Q: Does "enrichment" (house or extra tubes, shredded paper, etc.) interfere with activity monitoring? RENÉ: The PIR sensor is detecting heat, so it wouldn’t be a problem with shredded paper and similar material, but if you have a lot of solid houses, tubes etc. this would have an impact. On the other hand, they will typically not be active inside these shelters. Q: What is an estimated cost for the HM-2 system? RENÉ: The cost of an HM-2 system varies. Please contact us by phone or email so we can find out more about your needs. Q: How do you implant a microchip into a mouse? RENÉ: The microchips are delivered in an injection tool, sterile packed and ready to use. Standard sizes 12 mm in length by 2 mm in diameter down to 7 mm in length by 1.4 mm in diameter - can be simply and humanely implanted subcutaneously in the neck of an animal. The tool is designed to be minimally invasive, however this routine might require some experience to handle the animals while injecting. For mice, some users prefer to anesthetize the animals during injection of the microchip. Q: Are the RFID chips reusable? If so, how many times can they be re-used? Are there any steps required to recondition the chips (i.e. batter replacement, etc.)? RENÉ: Yes, the microchips are reusable and we do have customers that do this. However, the RFID microchips are relatively inexpensive, and most users figure that the cost of labour to remove, refurbish and re-sterilize exceeds the cost of the chip itself and decide not to go with this option. Q: Would the RFID chips work with DEXA measurements? RENÉ: The microchip should not have any effect on x-ray equipment and visa versa.
Q: Will the RFID chip interfere with NMR determination of body composition or blood flow to brown adipose tissue stores? MADS/NIELS: The RFID chip does interfere with an MRI scan. This is based on experience in the Kjolby lab (Department of Biomedicine, Aarhus University, Denmark) where we use ECHO-MRI-100H for mice. Regarding brown adipose tissue (BAT), it is not necessary to place the RFID microchip exactly on top of the BAT stores. You can place it more laterally or in the belly. We chose to place it in the neck to ensure the mice do not have easy access to the wound, so the incision was made in the neck, and we tunneled the chip in 1.0 - 1.5 cm caudally and 0.5 -1.0 cm laterally to the midline – so not on top of the interscapulum BAT stores. Furthermore, we have not observed any change in the appearance in BAT on gross examination in the mice Q: Do researchers set a pre-determined meal size and inter-meal interval to then generate meal number and pattern? Is it possible to control food and water access? RENÉ: A meal consists of a number of bouts which are not separated by more than the “Maximum Bout Interval”, MBI. The meal length begins when the load cell gets unstable and ends by the animal leaving the channel or the load cell stable period > MBI. The MBI is user configurable with the default set to 30 seconds. No predetermined meal size and inter-meal interval is necessary to generate meal number and pattern. Food and water access control can be done manually using the channel lock. Simply slide it in front of the channels. Especially for mice the channel lock has marked positions that support restrictions on only one channel. You can generate a chamber event report to document this. Q: Can you comment or elaborate on use of a system like the HM-2 to administer drugs via food/water intake? RENÉ: The HM-2 system is perfectly fit for these kinds of applications. You get the individual consumption of food and water and therefore you know exactly how much drug they have ingested regardless of the drug being in the food or water. Q: Would this system work (be able to detect feeding behavior) for high fat diets (HFD) that are given for a limited time every day while the animal's chow diet is still available? RENÉ: Yes. If you place the HFD in the two channels and just have the chow and water in the lid you would get individual consumption of the HFD and the feeding behavior on this. Q: For Niels, I missed bit of what you said when you presented the Leptin test data, how can you tell when the mice are ready for injections? NIELS: There are two considerations that I normally factor in. First of all, the animals have to habituate to the system and have a stable food intake you can use for a baseline. Around three days is usually enough. Secondly, you should train the animals in the procedure you are doing – in the case of the leptin test it is I.P. injections. I inject the animals with a small dose of saline I.P. every day at the same time they would
receive the dose in the test. Then I make sure there is no deviation in the data from the observed baseline – meaning the animal is not stressed. Stress due to handling/injection could delay/alter food intake and confound the experiment. After 2-4 training injections I check that the animals are on their baseline intake and therefore stress free when they receive the actual (leptin) injection. Then it is all systems go with the test. Q: Is it possible to use a liquid diet (in a bottle) instead of pellets in the system? RENÉ: Yes. We would work with you to find the best fitted bottle and cap for this application. Or maybe we would go for a different food hopper. It really depends on the liquid foods viscosity. We have done projects with a lot of different textures over the years. Q: Can you refill the food & drink dispensers without interrupting the session? RENÉ: Yes. Because of the system being event based. The food/water is measured before and after animal entry. The only thing you need to ensure, is that there are no animals inside the channels. Close the channels and do the husbandry and open again. Q: How does the system handle animals that hoard? RENÉ: The channels are tight to fit the species and the bottom is made of a grid plate. Furthermore, the bars in the feed hopper are closely fitted, which makes it hard to pick any larger pieces out without it falling into the spillage tray underneath. Q: What is the best way to measure pill intake (e.g. 1 pill per day per rat)? RENÉ: The food hopper is usually filled with chow e.g. We cannot regulate the amount of food, but only register the consumption by weight. We have customers testing compounds suspended in either water or in the chow, and you can of course PO dose your animals and then measure food intake. Q: Will ICV cannulation be a problem for feeding tunnel? RENÉ: This really depends on size of the animals and the design of the ICV. We have a channel that should work, but it would have to be tested. The concern is that the ICV could get stuck in the bars of the food hopper, but we can offer a different hopper were the animals have to reach into a container instead. This is usually used for powder feeding. Q: Can we dose just once a day? RENÉ: The HM-2 system can handle as many dosing procedures as planned for. You can either give the animal 1-2 or 3 dosage compounds per weighing or you can plan for as many as you want during the day(s).
If you have additional questions for René, Mads or Niels regarding content from their webinar or wish to receive additional information about monitoring food intake, water intake and ingestive behavior in group-housed rodents, please contact them by email:
René Vestergaard, Sales & Marketing Manager, MBRose ApS
[email protected] Mads Kjolby, MD, PhD, Assistant Professor, Aarhus University
[email protected] Niels Wellner, PhD, Post-Doctoral Fellow, Aarhus University
[email protected]
MBRose ApS Bymarksvej 15 5600 Faaborg Denmark email:
[email protected] Phone: +45 63 61 00 31
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