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National Research Council (US) Institute for Laboratory Animal Research. The Development of Science-based Guidelines for Laboratory Animal Care: Proceedings of the November 2003 International Workshop. Washington (DC): National Academies Press (US); 2004.

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The Development of Science-based Guidelines for Laboratory Animal Care: Proceedings of the November 2003 International Workshop.

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Breakout Session: Assessment of Nonhuman Primate Enrichment— Science Versus Welfare Concerns

Leader: Carolyn Crockett

Rapporteur: Randall J. Nelson

Participants discussed the questions and topics that appear below.

  • What is the scientific basis or peer-reviewed literature that influences or drives the assessment of enrichment for nonhuman primates (NHPs)?
  • What other influences or factors are involved?
  • Where are the gaps in our scientific knowledge?

Participants outlined the following benefits of performance standards for assessing environmental enrichment in NHPs:

  • Promote normal behavior: Stimulate a range of normal behaviors, thereby preventing or reducing the development of abnormal behaviors.
  • Reduce abnormal behavior: Redirect activities from abnormal to normal; provide outlets for behaviors that might otherwise be self-directed and possibly injurious.
  • Reduce stress and associated physiological imbalances: Increase the ability of the animal to cope with potentially stressful laboratory experiences.
  • Improve research: By making a healthier research animal (e.g., with normal physiological values), and by reducing subject attrition from development of severe behavior disorders.
  • Other possible benefits.

Other reasons for providing environmental enrichment for NHPs include:

  • Satisfying public opinion: Providing visible evidence (e.g., enrichment items) that animal welfare concerns with respect to behavioral management are being addressed.
  • Complying with laws: In the United States, complying with the animal welfare regulations requiring environmental enhancement plans adequate to promote psychological well-being.
  • Motivation of workers (technicians): Fortifying the value of the work and its scientific benefit.
  • Other possible reasons.

Participants also discussed the assessment of environmental enhancement for nonhuman primates. Discussion topics included use, other benefits, costs, scientific evidence, research protocol constraints, species considerations, and other considerations, as outlined below.

Considerations for Enrichment (Scientific evidence supporting use or other benefits vs. professional opinions or anecdotal evidence):

  • Use; preference
    • Percentage of time budget devoted to use of item
    • Choice; simple preference testing
    • Economic models: Elasticity of demand; change in consumption or usage when made more costly
  • Other benefits
    • Facilitating a variety of normal behaviors
    • Reducing abnormal behavior
      • Duration of reduction
      • Generality of reduction (i.e., all or selected undesirable behaviors; e.g., locomotor stereotypy vs. potentially self-injurious behavior)
    • Reducing stress
      • Cortisol
      • Other physiological measures (not yet identified)
      • Behavioral measures of (dis)stress (not yet identified)
    • Other
      • Improving overall health (measures, to be determined)
      • Possible others
  • Costs
    • Monetary cost
    • Time cost: implementation, sanitization, etc.
    • Risk: injury, disease transmission;
      • biosafety concerns for personnel
    • Rebound effect; increased cost if enrichment conditions are changed; social and physical
  • Research protocol constraints
    • Good laboratory practice; toxicology
    • Testing; sampling (leaving home cage, perhaps)
    • Infectious disease
  • Species, gender, age considerations, variability
    • Individual differences exist and are noticeable in NHPs
    • Extent to which maladaptive behaviors are caused by environment or inherent in the individual (neurochemical imbalances, organic disease, i.e., need for analgesia in experimental or naturally occurring procedures)
    • Changes in caretakers
  • Other considerations (may affect costs)
    • Documentation of benefit (or lack thereof)
      • Appropriate documentation and person who reviews it
      • Existence versus benefit
      • Determination of intra- versus interinstitutional variability
        • —Degree to which literature can suffice, especially with individual NHP variations
      • Communication with others: veterinarians, principal investigators, IACUC members
      • Novelty (i.e., whether variety within this category is necessary to achieve measurable benefit)
      • Frequency of providing this category of enrichment to achieve measurable benefit
      • Other possible factors

Minimum Standards (scientifically or anecdotally based) (Context-dependent variables should be considered):

  • Structural enrichment
    • Perches in cages; climbing structures in larger group enclosures
      • NHPs prefer perches in preference studies, but may take a few days to adapt. “A useful furnishing.”
    • Visual barriers: “privacy panels” in cages, barrels, etc., in enclosures
      • Probably reduces contact aggression and allows withdrawal. However, data are scarce, and most are anecdotal.
    • Other possible factors
  • Manipulanda (relatively durable items)
    • “Toys” in cages
    • Mirrors on cages; allow control of environment (viewing of conspecifics)
    • Determination of whether behavioral (experimental) manipulanda constitute enrichment
    • Habituation to items should be avoided and individual variations recognized
    • In the “wild,” youngsters play quite a bit with toys. More individual differences characterize adults.
    • The cost is low; the potential benefit high
  • Simple food treats (not foraging)
    • Produce
    • Other (peanuts, pasta, etc.)
  • Foraging
    • Devices such as puzzle feeders, foraging boards
      • Complex versus simple
    • Frozen treats or complex items for browsing, which also prolong consumption time
    • Floor substrate (bedding or woodchips) in group rooms
    • Special discussion about foraging
      • Should tasks performed for food or drink reward count as “foraging” (if “foraging” experiences specifically required by regulations)
  • Special enrichment items (non-food based)
    • Grooming boards (fleece, turf); paint rollers
    • Destructible: paper, cardboard, wood pieces
    • Other possible items
  • Sensory enrichment (visual, auditory, olfactory)
    • Video, television
    • Murals, colorful shower curtains
    • Music, natural sounds
    • Smells, aromatherapy
    • Windows (to outside, to inside corridor, to other animal rooms)
    • Light level; light cycle
  • Spatial
    • Cage size: Participants did not discuss this topic, but instead reached consensus that cage size should be sufficient to accommodate all agreed-upon enrichments and to permit normal postural adjustment.
    • Cage level
      • Animals prefer to observe from above, but there is not necessarily a physiological difference to accompany this.
    • Periodic access to larger “activity cage” (frequency, duration)
  • Social Contact
    • Tactile social contact with conspecifics
      • Degrees and type of conspecific contact: visual-only, grooming-contact, pair, small group, typical species-specific group, same-sex, opposite sex, ages, full-time, periodic
        • —Age at weaning
        • —Age at first single housing
        • —Proportion of immature developmental stages spent in single housing
    • Compatible human caregiver versus same species versus “compatible” species; determination of whether human contact can compensate for individual housing
      • Structured human contact (training) versus simple contact (e.g., providing treats). Training is beneficial but not a substitute for conspecific contact.
      • Habituation to caretakers, handlers, experimenters can be beneficial, as can consistency in surroundings. A balance is essential.

Discussion points included the observation that some who conduct enrichment programs at their institutions may not be completely trained in the behavior of one or more species for which they are specifying enrichment programs. Enrichment effects are additive, and it is difficult to examine the pieces in isolation. The whole may be greater than the sum of the parts.

The consensus of the group was that when the science is not available, expert opinion should be used. With regard to who has the expertise, participants stated that it depends on who has the most experience with the individual NHP in question. The team approach is crucial when establishing the best/good practices to be implemented under the institutional and experimental constraints at any given location. In summary, a cage size should be used that is sufficient to accomplish appropriate enrichment and species-specific behaviors.

Copyright © 2004, National Academy of Sciences.
Bookshelf ID: NBK25421

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