The University of Iowa

Humane Intervention Points (Guideline)

Guidelines: The IACUC has provided a set of guidance documents (Policies, Guidelines, and Informational Sheets) for use when planning animal procedures at the University of Iowa. An exception to a Guideline must be described and justified in the Animal Protocol and approved during the normal review process.


The purpose of these guidelines is to provide a set of regularly used criteria for the establishment of humane intervention points for research animals at the University of Iowa. These guidelines are intended for use in writing humane study endpoints, whose purpose is to prevent or minimize animal pain or distress during research activities.  


  • Humane Intervention Points:  a set of predetermined physiological or behavioral criteria that define the point at which humane intervention must be implemented to prevent or relieve unnecessary pain or distress in a research animal. Humane intervention points function as an effective way to refine research and ensure accurate and timely data collection.
  • Humane Interventions include but are not limited to those listed below:
    • Provide adequate veterinary treatment to alleviate pain or distress, such as analgesia and/or supportive therapy to the animals (ie. fluids, dietary supplementation such as providing Diet Gel, heat, etc.)
    • Cease performing experimental procedures that contribute to pain or distress until the animal recovers
    • Remove the animal from the study
    • Increase the frequency of observation to ensure early identification of pain or distress
    • Euthanize the animal
  • Experimental endpoint: the point at which scientific aims and objectives have been reached
    • Not all animals will reach this point, if humane intervention criteria occurs and treatment does not alleviate pain or distress
  • Pilot Study: a preliminary study used to determine appropriate humane intervention points in cases where the course of disease, experimental effects, or indicators of distress are unknown
    • An IACUC approved Animal Protocol is required to perform a pilot study
  • Training Animals: animals used in cases where individuals need to develop skills and become competent in procedures, in addition to those used to refine a procedure.  Includes an animal carcass or an animal used in a terminal/non-survival procedure.
    • An IACUC approved Animal Protocol is required to use training animals
    • Training animals reach their humane endpoint when the training objective is complete; they are not used to collect subsequent data
    • Different humane endpoints may be needed for training than for data collection
  • Scoring System: a method of animal evaluation in which numerical values are assigned to specific clinical signs and/or behavioral observations
    • Humane intervention points are predetermined and based on the total numerical score assigned to each established criteria
    • Numerous scoring systems are already established and published in scientific literature
    • Consult OAR or IACUC Veterinarians for guidance in establishing a new scoring system

Establishing Humane Intervention points

  • Determine what humane intervention points and what interventions are appropriate for the study
    • Use objective, measurable parameters when possible to designate the points at which intervention occurs
    • Ensure monitoring frequency, humane intervention points, and interventions are clearly defined in the Animal Protocol
  • Ensure all personnel responsible for making animal observations have been adequately trained to observe, recognize, and document the intervention point parameters as approved in the Animal Protocol


Commonly used Humane Intervention Points


Criteria at which intervention or euthanasia must occur unless scientific justification is provided and approved in the Animal Protocol include (but are not limited to) the following:

  • Weight loss
    • For acute infection studies, ≥20% weight loss compared to the weight at the start of the experiment
    • For chronic/long-term studies (especially of juveniles), ≥20% weight loss compared to control animals or animals of a similar age (preferably sharing the same background strain)
  • Body Condition Scoring (BCS)
    • For mice, a BCS of less than or equal to “2” out of “5” (BCS  2) on the scale from Ullman-Cullere, et al. 2 
    • For rats, a BCS of less than or equal to “2” out of “5” (BCS ≤ 2) on the scale from Hickman and Swan, et al. 3
    • For other animals, the BCS scale used should be defined or referenced
  • Inability to rise or move about the cage/pen
    • Access to food and water is impaired
  • Discrete Tumors
    • Ulceration, necrosis, or infection
    • Interference with normal posturing or ambulation
    • Size
      • For mice, 2 cm in diameter by any measurement/in any dimension
      • For rats, 3 cm diameter by any measurement/in any dimension
  • Metastatic/Disseminated Tumors
    • BCS ≤ 2
    • Increased respiratory rate or effort
  • Dehydration
    • Delayed skin tent
  • Labored breathing
  • Neurologic signs severe enough that they prevent normal eating/drinking
  • Bleeding that cannot be readily stopped
  • Self-induced trauma that creates wounds
  • Post-surgical complications
    • Dehiscence or infection of surgical site
    • Signs of systemic infection (lethargy, hunched posture, increased respiratory rate)



Stating that animals will be euthanized when they become moribund is not an appropriate humane intervention point as this term is subject to individual interpretations. In addition, it can be assumed that the moribund animal has experienced significant distress in the period leading up to the moribund condition. The purpose of identifying humane intervention points is to prevent or minimize animal pain or distress.


Death as Endpoint

The continuation of a study until an animal dies is almost never acceptable. Strong scientific justification is required for such a study. Contact the Office of the IACUC for further guidance if animal death is a necessary endpoint.



1. National Research Council. Guide for the Care and Use of Laboratory Animals: Eighth Edition (p. 27). Washington, DC: The National Academies Press; 2011.

2. Ullman-Cullere MH, Foltz CJ. Body Condition Scoring: a rapid and accurate method for assessing health status in mice. Lab Animal Science; 49(3): 319-323, 1999.

3. Hickman DL, Swan M. Use of a body condition score technique to assess health status in a rat model of polycystic kidney disease.  J Am Assoc Lab Anim Sci. 2010; 49(2):155-9.


Last Reviewed by the IACUC 3/09/2022