Hi Jo,

have you considered probe placement as a source of lower temperatures. While it was never a problem in rats as they have a thick abdominal muscle and thick fur, in mice I found that a "wandering" emitter meant that in some animals the probe would migrate to the front abdominal wall, then when they laid down on a cold cage bottom it would affect the accuracy of the temps. When the animal was laying down or otherwise touching the bottom of the cage temperatures would drop by a few degrees at times. Once I started using the small loop on the device to suture it to the back of their interperitoneal cavity I never saw the problem reoccur. It is a bit more a hassle as you have to displace their viscera slightly during surgery so you can suture the device to the back of their abdominal wall, but it worked very well for protecting the data and getting more realistic core body temp readings. I haven't had the same problem since.

Hi Ian,  Your comment is right on. Indeed I did not anchor the transmitters when I implanted them. I just dissected the animal with lower temperature reading yesterday, and found the transmitter was herniated into the scrotum. That explains the 3 degree C lower than rectal temperature after the implantation but normal reading during the calibration prior to the implantation. Thank you very much for your helpful information, and I will anchor the transmitters with suture as suggested in the future. I guess that a larger incision at abdominal muscle will be needed during the implant surgery than what I did last time.

 You would be surprised. Now that I have practice the incision need be no larger than the probe. Just pre-tie the probe securely to some non-absorbable suture, insert the probe into the incision then move the visecera to the side till you can see the rear abdominal wall, hook the suture through some muscle/tissue at the back and then gently tug to pull the probe backwards while jostling the belly a bit and the intestines should make way. After my first few I could do it with an incision no larger than the diameter of the G2's but yeah it'll take some practice. Good luck!

I concur with other commenters, the mini miters are generally reliable for us for monitoring core body temp and HR in mice at room temperature, and somewhat less reliable during cold challenges.  We need about a half inch incision, and also tack to body wall.  We always test them before implantation, and occasionally detect ones that are off and send them back to the company and do not use them for the study.  There is great value in obtaining this information in unrestrained and unstressed animals.  Obtaining rectal temperatures in awake mice will cause a stress induced increase in the temperatures, and of cours obtaining the rectal temperature in an anesthetized animal is problematic.