Frequently Asked Questions

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Which kind of bedding is used at InVivos?

We use Tapvei aspen chip (5x5x1mm), it comes in 10Kg fibre bags.  The chips are heated at 100- 120˚C, screened and sieved under constant monitoring. The end product is practically dust-free and is ideal for not only mice, rats, guinea pigs, hamsters and gerbils but also for hairless animals. The bedding is very absorbent, circulates well and does not clot.

How many animals does InVivos deliver per cage?

All InVivos mice and rats are packed into the Taconic Transit Cage TTC™ (TTC™) while they are in their Barrier Breeding Room. The number of animals packed in each TTC™ varies depending upon the age and size of the animals. To find out more, please enquire with our Customer Service.

Does InVivos carry any research animal models that are not in the catalogue?

For any enquiries on animal models not found in our catalogue, please contact our Customer Service.

What is the best host for xenograft studies?

The most appropriate answer to this question is that it depends on the cell line(s) to be used – any cell line may have performance that varies from one host to another.

There are, however, some factors to consider.

Nude vs. Scid

All nude mice are T cell deficient. That is the minimum requirement to host a human tumor graft. Most of the tumor lines we have worked with grow quite well in the basic nude mouse. SCID mice are also T cell deficient, and are B cell deficient too.


Inbred vs Outbred

InVivos provides these immune deficiencies on outbred backgrounds (NCR nude) and also on inbred backgrounds (BALB/c nude, CB.17scid). The outbred versions tend to be larger and have a greater tumour take rate. Since they produce larger litters, we can offer them at lower prices. The use of an inbred model offers more consistent (homozygous) background genetics.


Role of NK cells

Certain cell lines may be susceptible to NK cell activity. In this case, a mouse that is also NK cell deficient may be necessary. Taconic models which lack T, B and NK cells include the Scid-beige and the CIEA NOG mouse®. The CIEA NOG mouse® is the most immunodeficient mouse available. Currently, InVivos does not breed these two strains in our facility. It has superior engraftment capability and is a good model to try if you experience low take rates or inconsistent growth in nude or scid models.


Cell line history

Recommended course of action.


  1. Consult the literature to determine which host animals have been used for the cell line, or cell type, you wish to use. Beware of papers that use the nondescript term “athymic nude mice.”
  2. Determine if your study requires an inbred host. For studies that use the mouse as a tumor host, and study a drug:tumor interaction, an outbred mouse is often sufficient. Studies which target the mouse response to a xenograft may utilize an inbred host to present consistency from one animal to the next within study groups.
  3. Perform a pilot study with the simplest solution. The NCR nude mouse and ICR scid mice are both cost-effective solutions and should be ruled out before more expensive mice are considered.

Can I obtain a health report with my delivery?

Yes you can. However this will be a copy printed from our website. The latest health reports are signed by our attending veterinarian and are available for download HERE.

How does InVivos report gestational age of timed mated animals?

The InVivos convention for timed pregnancy identifies the first day of pregnancy as the morning on which mating plug was observed. This is called day 0 of gestation.

Do nude mice and rats have any hair?

Yes, they do. Nude mice and rats may have very sparse hair on their bodies and around their face. The hair growth cycle in these animals does persist with hair regrowing on an average frequency of every six weeks or so. This will be a transient regrowth and will not persist very long. This does not affect their genetic immune deficiency, but may have subtle impact. For example, nude rats may require shaving prior to surgery. Even in their hairiest presentation, nude rats will be easily identified.