Castration eliminates conspecific aggression in group-housed CD1 male surveillance mice (Mus musculus)

Dear Editor,

I just read the article entitled “Castration eliminates conspecific aggression in group-housed CD1 male surveillance mice (Mus musculus)”¹ and would like to comment on the materials and methods and statements.

First, although I applaud the authors’ concern for the welfare of fighting mice, surely intermale aggression could be avoided by the simple expediency of using only females. However, even if males must be used and castrated, I have an issue with the statement in the Discussion “the castration method used did not expose a body cavity…”¹ In the description of the surgical castration, the authors state that “An open castration was performed, followed by separate closure of the body wall and skin…”,¹ and the photo caption says the vessels were ligated separately. So, the authors have contradicted themselves; an open castration means opening the vaginal tunic, which is the body wall, thus exposing a body cavity. If they had really done a closed castration, exposing the testicles within the vaginal tunic and ligating around the tunic, that would have been preferable, particularly because there was no type of draping material (pulling the testes through a small opening in a disposable drape would have avoided the possibility of contamination via unprepped hair, etc). In the photos, blood was obviously on structures around the prepped area.

Our IACUC banned the use of 2, 2, 2-tribromoethanol several years ago; at that time it was not available in a pharmaceutical grade and required reconstitution. Perhaps this is no longer the case. However, if the 2, 2, 2-tribromoethanol merely induces narcosis and not analgesia, it would seem incumbent on the authors to provide analgesia, as with concurrent buprenorphine, to avoid pain.

Finally, the choice of 5-0 silk as a suture material is a concern. Our institution accepts nonabsorbable suture only for very short-term subdermal use in recovery surgeries. I assume that these mice will stay alive for several months as sentinels. Was histology done on the area of these sutures to look for inflammation? Braided 4-0 absorbable suture would be an affordable and appropriate alternative material.

Sincerely,

M Lynne Kesel, DVM
Clinical Veterinarian, Laboratory Animal Resources Associate Professor, Animal Science Department Colorado State University