Humane Endpoints Policy


Compliance with all governing regulations involving humane care and use of animals in research is mandatory at Boston University. Legal, ethical, and regulatory guidelines obligate all personnel involved with research protocols utilizing animals to ensure that animal pain, distress, and suffering is minimized.


A morbid state is a condition relating to, or typical of, disease or illness. Any animal exhibiting signs of morbidity should be reported to BU ASC staff.

A moribund state is defined as a state of dying. Any animal found to be exhibiting at least one of these characteristics is considered to have end-stage illness and should be euthanized immediately unless an exception has been specifically justified in the IACUC-approved protocol.

The IACUC requires investigators to humanely euthanize all animals discovered to be moribund rather than allowing them to die spontaneously. Euthanasia methods must be in compliance with the investigator’s approved IACUC protocol. Rare exceptions to this policy, for studies in which euthanasia prior to actual death would invalidate the experiment, will only be considered by the IACUC if there is a clear scientific justification.

Humane endpoints are criteria used to end experiments on individual animals in order to avoid or terminate unrelieved pain and/or distress. Once a humane endpoint is reached, the animal should be immediately euthanized or treated as described in the approved protocol.

Once animals start to display clinical signs of illness, investigators or laboratory personnel must monitor their subjects frequently (at least once daily or as described in their protocol) to ensure timely identification of moribund animals or animals for which previously defined humane endpoints have been reached (this includes weekends and holidays). Investigators are obligated to make every effort to identify and humanely euthanize moribund animals that have not responded to treatment. In general, experiments should be designed such that all procedures are completed prior to animals reaching a moribund state, also referred to as end-stage illness.

End-stage illness is defined as signs of a debilitating physical state where death is imminent and treatment ineffectual. Animals exhibiting severe signs of morbidity or a moribund state are considered to be in end-stage illness. Investigators should feel confident in judging the condition of their animal subjects, differentiating between a morbid and moribund animal, and be prepared to perform approved euthanasia when necessary. The following lists will aid investigators and laboratory personnel in identifying morbid and moribund animals. If there is any question or concern about judging the condition of animal subjects, please contact BU ASC veterinary staff.

All investigators and laboratory personnel utilizing animals in research need to be cognizant of the well-being of their animals. The health and well-being of research animals should be monitored at least once daily by animal care staff. Once clinical signs are observed (see below for examples), animals must be observed by the laboratory personnel at least once daily or as described in their protocol. If an animal is found to be moribund, it must be euthanized according to the approved protocol.

Clinical Signs of Morbidity in Animals

Note: This list is not exhaustive.

  • Hunched posture
  • Sunken eyes, with or without discharge
  • Respiration that has increased, decreased, or appears labored
  • Rapid weight loss (more than 10% of body weight within a one-week period)
  • Total weight loss (>20%) from baseline for mature animals on short term studies or from as age adjusted growth chart for a particular vendor strain for your or growing animals.  (Note:  Weight loss criteria for young, growing animals is different than for adult animals. In general, weight loss from baseline is not acceptable for growing animals; rather, a “reduced weight gain” protocol or a weight loss adjusted for age protocol if the strain data is published will be established on a case-by-case basis depending on the study, species, and strain.)
  • Decreased body condition score (2.5 or less on a scale of 1–5; see species-specific guidelines for assigning a body condition score)
  • Decreased or no intake of food
  • Hypothermia or hyperthermia
  • Ruffled hair coat, erection of hair or fur, lack of grooming behavior
  • Diarrhea or constipation
  • Vomiting
  • Unsteady gait or lameness not induced by experimental manipulation
  • Ulcerated tumors
  • Severe or ulcerative dermatitis
  • Inability to reach food and/or water (access to food and water must be given, e.g., food on floor and Napa Nectar, or the animal humanely euthanized)

Clinical Signs of Moribund Condition in Animals

Note: This list is not exhaustive, and, in general, includes the list of symptoms above for morbidity, but with a higher degree of severity.

  • Impaired mobility (the complete inability to reach food and water)
  • Inability to remain upright
  • Hunched posture for more than 48 hours
  • Labored breathing and cyanosis (skin or mucous membranes have a blue color)
  • Clinical dehydration and/or prolonged decreased food intake (more than 48 hours)
  • Muscle atrophy and signs of lethargy and lack of physical activity
  • Severe, rapid weight loss and emaciation (more than 20% of body weight from baseline; body condition score of 1.5 or less on a scale of 1–5; see species-specific guidelines for assigning a body condition score)
  • Chronic diarrhea or constipation for more than 48 hours
  • Hematological or biochemical values that indicate organ failure
  • Prolonged bleeding from any orifice
  • Self-mutilation
  • No response to external stimuli

BU IACUC Approved April 2010, Revised January 2014