Multiple Survival Surgery

Major vs Minor Surgery

Oocyte Removal from Xenopus

Major vs. Minor Surgery

Surgical procedures may be categorized as major or minor, based on the USDA’s description:

Major operative procedure means any surgical intervention that penetrates and exposes a body cavity or any procedure which produces permanent impairment of physical or physiological functions1.

Regardless of whether they are categorized as major or minor, multiple surgical procedures on a single animal should be evaluated to determine their impact on the animal’s well-being.

Multiple major surgical procedures on a single animal are acceptable only if they are:

  • Essential components of a single IACUC-approved research project or protocol;
  • Scientifically justified by the investigator; or
  • Necessary for clinical reasons.2

Animals should not undergo surgical procedures under more than one protocol, except under a few limited exceptions, such as vendor-performed ovariectomy or neutering performed by campus veterinary staff.  All surgeries performed on a single animal must be interrelated components of one project.

Cost savings alone is not a justification for multiple surgical procedures; however, conservation of scarce animal resources may be considered as part of a scientific justification by the IACUC. 

Oocyte Removal from Xenopus

One exception to the general rule against multiple survival surgeries is the harvest of oocytes from Xenopus species.  The IACUC acknowledges that the quality of oocytes varies a great deal from animal to animal; maximizing the productivity of a single “good producer” enhances the reproducibility of critical experiments and may reduce the overall number of animals used.  While the harvest of oocytes meets the definition of “major” surgical procedure, the procedure is quickly performed by appropriately-trained personnel and the animals rapidly return to normal feeding and activity. 

Guidelines for Multiple Oocyte Harvest:

  • The maximum number of surgeries allowed per animal is six, three on alternating sides, with the sixth surgery being a terminal procedure.
  • The interval between procedures should be not less than one month.
  • The protocol must include a written description of the method used to identify animals to ensure adequate time has lapsed between surgeries (e.g., skin marking or tattooing, tank rotation, etc).
  • Aseptic technique appropriate for aquatic species must be used to reduce microbial contamination.
  • General anesthesia such as MS222 must be used
  • Recommendations in the IACUC Surgery Policy and Guidelines for aquatic species must be followed.
  • Animals should be housed singly and carefully monitored for 24-48 hours post surgery.
  • Skin sutures and wound clips, if non-absorbable, must be removed 2-3 weeks after surgery.


1 9 CFR Chapter 1, Part 1.1
2 Guide for the Care and Use of Laboratory Animals, 8th edition, page 30.

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