This may be a simple question, however, I face this problem every day. As you aware, there is a need to analyze the weight of the animal during study period. While weighing in an electronic scale, the rats are moving and the number in the digital screen keeps on changing. I used to record a number (which I observed frequently) from the screen as weight.
I don't have an idea on how to deal with this practical problem. Please share with me any useful tips to weigh a laboratory rat with accuracy.
Thanking you in advance for your answer.
The simplest would be to place it into sleep... Then again you might not be able to do so. What might be more practical would be to take the average value of your readings, i.e. increasing the time constant of your scale.
If you have an analog output, you can just feed it into a RC network buffered by an op amp http://en.wikipedia.org/wiki/Op_amp_integrator the time constant is then R1.Cf and you can set that value to be longer than your rat ability to jump (a few seconds should do).
If you have a serial output to a computer, you can do the same digitally. Simplest is to read and add N consecutive samples, and divide the resulting value by N. Here again, you should read a total time of a few seconds, i.e. accumulate N=Fs.T with Fs sampling frequency and T time in seconds.
As your rats become accustomed to the procedure they should move around much less and the process of weighing them should get easier. We use a balance that has "dynamic weighing" capabilities for especially designed for mice/rats (these can be purchased commercially).
The only other "cheap/free" option could be to build a "stand" or "perch" of some sort, potentially you could train the rat to sit or grasp the stand and that may keep them entertained long enough for the weight of the balance to stabilize. Piere's suggestion looks good too!
When I weigh my mice I place them in a deep container on the scales and generally find that they stay still initially when I put them on there, then if I leave them for longer they become more comfortable go exploring and the weight changes.
You probably don't need the rat's weight in grams to 3 decimal places, so make life easier for yourself and choose scales that increase by 1 or 5 grams, as this is probably accurate enough for your measurements and will have less variation as the rat moves. Hope this helps :)
For mice and eats, our lab will simply place them in a plastic beaker. We tate the scale after we put the beaker on. Generally we have no problems with this method since the plastic is smooth and they have a hard time getting out.
hi,
As said by Gough G Au, the rats will start to be used to be weight. They move a lot because of the stress. When I weight them I place them in a large bol and I try to be gentle and calm with them. If you take your time to weight them they will be calm and they won't moved a lot in the bol. But if you try to weight them as fast as you can it will be a problem. I usually place my hand on the top of the bol to make them calmer.
hope it will helps
As mentioned it's a simple procedure. PLace a large plastic bowl/ beaker on the weighing scales, tare the scales back to 0, take the bowl off, place your animal gently in the bowl and place it back on the scales. If you animal has excessive rearing behavior which causes the numbers on the scale to jump around, you can hover your hand over the top of the bowl, in particular near their nose when they rear up. They usually go back down again when their whiskers hit your hand. You only need 1 second or so of still to note the weight.
At our lab, we use a lightweight aluminum container, with a lid. The lid prevents the rats from rearing up, and if they move around laterally, it does not change the reading very much. As someone else mentioned, it only takes a couple seconds of stillness to get an accurate reading.
I have never worked any where that they did not have a scale expressly for weighing rats and mice. However, every answer above, except the one about putting them to sleep, is correct. Further, you should have had training in this - if you plan to publish in a journal, you're required to have an IACUC committee, and there is training for people who are going to be handling animals. It is also available on line through Citiprogram. Good luck. The first time I ever weighed a rat, I was scared to death as they had never been handled and I had NOT been trained!!
think logically - Archimedes solved a similar problem some 3000 Years ago...
I was going to suggest exactly the same as Lukas Peintner did but Thomas J R Beveridge approach is correct and more straight forward. Rats tend to be well behaved unless there's something wrong with them, us or the surroundings.
I've used the container method for mice as well (albeit much smaller container). I found that it helps to have a lid for the container. Otherwise I do it the same way as Thomas J R Beveridge.
Like Ellen Lark said, a transparent box with a lid is the best method to weight mice. If you add a paper tissue to it the animal will hide and relax.
Thomas J R Beveridge have detailed the method which is in regular practice. Observe the readings for 2-3 sec and record the value which appears more times during up and downs.
I don't understand why no-one suggested the most obvious solution - unless I am missing something?! Just use a set of scales that averages the readings for you! most electronic scales for weighing rodents have this averaging function... after 2-3 seconds you get an averaged reading - you can repeat this to see how accurate it is. In my experience, it is very reliable.
Hi Annadurai Shanmuganathan ,
Yes but you can use the following balance to weigh the animals (mice/Rat/Guinea Pig/Hamster).
It is useful, we use to this in lab routine for animals.
Thank you,
Good luck
Hi All,
I know this is an old thread. I was wondering if anybody would be interested in monitoring weight and heart-rate without human intervention. The tube shaped device is fully autonomous and last up to 2 weeks. It will tell you when the rodent pass, and if signal is good, measure weight and heart Rate. It doesn't stress the mouse, completely passive. Limited to 1 mice per system for now. If Anyone interested, please let me know,
Thanks,
Christophe
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