Multidimensional Cost–Benefit Analysis to Guide Evidence-Based Environmental Enrichment: Providing Bedding and Foraging Substrate to Pen-Housed Monkeys

Abstract

Refinement of animal care and housing is an important shared goal—and challenge—of the team of research, veterinary, and animal care personnel charged with ensuring the wellbeing of laboratory animals. This study addresses 2 issues central to decision-making and implementation of environmental enhancement: methods for useful and comprehensive cost analysis and evaluation of engineering, husbandry, and facilities considerations. The study was undertaken to analyze the feasibility and cost of providing wood shavings as a floor cover for pen-housed monkeys. The beneficial effects of bedding for the welfare of laboratory-housed animals have long been validated. Our study illustrates a workable team-based procedure for comprehensive cost analysis of an important environmental enhancement and demonstrates that the animal welfare benefit is accompanied by decreased husbandry costs. An engineering solution to the potential challenge that wood shavings pose in terms of clogging water pipes was successful. Another successful outcome was the reduction in water (estimated at 192,000 gal annually) and chemicals used to clean housing areas. Emphasis on rigorous evaluation and objective measures of cost and benefit, as well as inclusion of the many factors and teams involved in animal research, holds strong potential for building a better foundation from which to contribute effective changes and improvements in laboratory animal welfare. Taken together, the findings of this study demonstrate that team-based, integrative, and scientific evaluation of environmental enhancement is an effective approach to guide selection of strategies with maximal potential for improving animal welfare.

Refinement of animal care and housing, one of the “3Rs”¹⁶ (reduction, replacement, refinement) that guide animal research, is an important shared goal—and challenge—of the team of research, veterinary, and animal care personnel charged with ensuring the care and welfare of laboratory animals. Decades of effort by behavioral scientists, enrichment specialists, veterinarians, animal care staff, laboratory animal facility managers, and others have resulted in many substantial improvements in animal housing and husbandry. These efforts continue in laboratories and facilities across the world. As a result, a large body of literature can guide not only implementation but also evidence-based decisions about which environmental enrichment or enhancement strategies provide maximal benefit to animal welfare.^3,14,17 The research and laboratory animal community also acknowledges common obstacles to continued progress, as well as gaps between the empirical literature, actual practices, and extant policies.³

One of the greatest challenges is deciding which refinement strategies should receive priority for implementation and determining how resources can be used most effectively to result in the highest likely benefit to animal welfare. Central to this consideration is development of useful criteria and methods for comparing the relative value of different enrichment, enhancement, and refinement strategies.^12,14,15 A large body of literature provides many resources for identifying techniques and tools aimed at improving laboratory animal welfare; however, essential information from which to compare their value is often uneven in inclusion, or missing altogether. Benefits of some specific methods of environmental enrichment are grounded in empirical study. Others lack scientific evaluation that could provide supportive evidence. Furthermore, relative costs of specific methods or strategies often are not calculated. Where costs are calculated, they are often placed in a very narrow context that does little to assist in cost–benefit analysis that is inclusive of the full range of considerations driving husbandry and enrichment decisions. For example, calculating the cost of constructing a novel foraging device is useful but hardly addresses the full cost of its implementation or sustained use. As a result, comparing the relative value of different devices, strategies, and tools is difficult.

The absence of more comprehensive information about the costs of specific strategies for environmental enrichment is a common obstacle to cost–benefit analysis and decision-making, because that information is essential to identifying how resources might be used most effectively to result in the highest likely benefit to animal welfare. Also critical to the analysis is consideration of costs beyond initial implementation. A key component of improving the care of laboratory animals is ensuring that those refinement strategies that are selected are successful over the long-term.¹⁴ An essential component to the long-term maintenance and success of a particular method is the extent to which it is adopted and supported at all levels and by the many different teams that interact in research settings, including animal care, research, behavioral science, facility, and veterinary personnel.¹² Therefore, attempts to select and implement enrichment strategies without recruiting team members from these different divisions to contribute perspectives and evaluate practical considerations often result in suboptimal long-term success. The full costs and benefits associated with enrichment, enhancement, and refinement techniques often is not reported in a way that is inclusive of the all aspects of the team involved in animal care. As a result, opportunities for accurate comparison of both cost and welfare value of different strategies are lost.

Fully or objectively accounting for all aspects of benefit or cost of different refinement strategies likely is impossible. In addition, real costs must be calculated at the level of individual facilities to provide accurate and meaningful information. However further development and evaluation of methods to encourage more comprehensive cost–benefit analysis and evidence-based selection of environmental enrichment and enhancement clearly has the potential to facilitate continued improvements in laboratory animal welfare. The scientific literature surrounding environmental enrichment of laboratory and zoo animals demonstrates the value of developing accepted professional standards and procedures to guide evaluation of strategies and techniques to improve animal welfare. Therefore, although specific methods and costs may vary by facility, the overall objective and standards remain consistent, with the expectation that full costs can—and should—be requisite to evidence-based cost–benefit evaluation of enrichment and to calculation of its relative value and effectiveness.

The study reported here is the result of an effort to develop a scientific, evidence-based approach to evaluate the feasibility and cost of providing a substantive environmental enhancement, wood shavings as a floor cover, for pen-housed monkeys. The goals of the study were 2-fold: first, to develop an effective engineering and husbandry strategy to prevent bedding from creating problems with drainage and pipes in the housing areas; and, second, to conduct a thorough cost analysis. The study was undertaken by a collaborative team (research, animal resources program, veterinary staff, and institutional administration), to provide a comprehensive evaluation and to incorporate diverse perspectives and expertise. The impetus for the study was from a research group (AJB, CAC, PJP) with a long-standing interest in providing bedding to animals in their research program. With the support of the Institutional Animal Care and Use Committee office and the Director of the Animal Resources Program, a collaborative team was assembled to design and execute the study.

The team first identified key members of different divisions whose expertise was essential to conducting the study and including assessment of full costs and benefits. Input, support, and feedback were solicited from a broad range of personnel by presenting the initial study design and then results from each study phase in various meetings. This process included small meetings with veterinarians and the enrichment coordinator, staff meetings attended by the animal care personnel, and meetings of the IACUC's subcommittee on nonhuman primate environmental enrichment. Informal interactions between team members and other key stakeholders also facilitated the work. For example, design of the drain covers was accomplished through interactions between the engineering department, operations manager, and research team. Additional explicit intentions of the project were to include the perspectives of all stakeholders affected by the husbandry change and to facilitate team-building. Therefore, considerable effort was made to solicit feedback through individual and group interactions, to make changes in process where needed, and to report back on progress and outcomes. Including personnel from different divisions made it possible to collect the broad range of cost data–including initial equipment, labor, consumable supplies—needed to compare husbandry and costs without provision of bedding with costs incurred when wood shavings were provided.

The selection of this specific environment enhancement strategy was guided by several considerations. Foremost was the demonstrated value of bedding and foraging substrate for wellbeing in nonhuman primates. In brief, a long-standing body of literature demonstrates that providing bedding material in animals' housing environments results in marked benefits to animal welfare and husbandry. Soft bedding (for example, wood chip shavings) not only provides a more natural substrate than are bare floors but also reduces aggression,¹ abnormal behavior,⁶ and overgrooming⁴ while promoting species-typical behavior (for example, foraging) in laboratory-housed monkeys.^4-7,15 Bedding provides a long-lasting and cost-effective means of environmental enhancement that improves cleanliness^8,9 while reducing labor, water, and chemicals used for cleaning.¹⁸

The second consideration in selecting this environmental enhancement strategy for comprehensive cost and engineering evaluation was the observation that provision of bedding for nonhuman primates in pen-style housing is not used widely in laboratories.³ This pattern likely is due in part to the number and types of obstacles surrounding its implementation. As such, bedding presents a good example of another key issue in refinement of laboratory animal care. In brief, many environmental enrichment techniques have been developed over previous decades and are now implemented widely. In some cases, however, those strategies and interventions aimed at improving laboratory animal welfare that have not yet been adopted widely are those that pose considerable practical challenges. Evaluation of whether additional effort to overcome those practical challenges is worthwhile can be guided by consideration of potential benefit to animal welfare. From this perspective, provision of bedding is one of the best candidates for additional effort because the scientific literature already provides ample demonstration of high benefit. Therefore, the potential high cost in addressing challenges to its implementation has a relatively high likelihood of being balanced by high effectiveness in improving animal welfare.

Although provision of bedding material has proven benefits to primate wellbeing, numerous potential obstacles to its use in laboratory environments exist. Two widely acknowledged challenges to using this technique for environmental enhancement are threats to plumbing and the perception of increased husbandry costs. Placing solid bedding on pen floors easily can result in clogging of the drains and pipes that carry water and waste from the animals' housing. The consequences of clogged drains and obstructed pipes include not only disruption of the animals during correction of the problem but also expensive repairs. Using bedding also requires changes to husbandry procedures and has the potential to increase husbandry and material costs; however, few data from direct, empirical study that could address this question are available.

Materials and Methods

Subjects.

Evaluation of the environmental enhancement strategy was conducted in a building housing a colony of 54 bonnet macaques (Macaca radiata) ranging from infants to mature adults. The monkeys were housed in 9 social groups in 16 indoor:outdoor pens (2.4 m × 2.4 m × 2.7 m per section). Each pen had epoxy-coated floors, 2 sets of perches (1.1 and 1.9 m from the floor) on each of 3 walls, and either bars (indoors) or screen mesh (outdoors) on the 4th (front) wall. The indoor quadrants each were fitted with 2 feeders and drinking spouts. The outdoor quadrants were equipped with swings constructed from a variety of materials. Transfer doors between adjacent indoor or outdoor quadrants allowed monkeys in large groups to have full access to all 4 quadrants. Pens were exposed to natural lighting from the outside. Inside pens were maintained on a 12:12-h light:dark cycle. Monkey chow (Purina 5038, Purina Mills, St Louis, MO) was provided twice daily in the morning and afternoon. Fruit, vegetables, ice cubes containing small fruit, vegetable, seeds, flavors, and colors, popcorn, or seeds were distributed each afternoon. Enrichment was distributed to multiple locations within the enclosures, including foraging devices, and in quantities that provided all animals with access to the enrichment. The study was conducted in compliance with all regulations, including the Institutional Animal Care and Use Committee of Wake Forest University Health Sciences and the NIH Guide for the Care and Use of Animals.¹¹ Animals were treated humanely, and there were no potentially painful procedures.

Materials.

Drain cover.

The facility engineer designed a drain cover (Figure 1) of opaque high-density polyethylene (16.5 × 31.5 × 0.78 cm) to prevent shavings from clogging the plumbing of the animal housing building. The drain cover fit flush to the drainage grate and was attached to the grate with a spring loaded T-hook mechanism constructed of 0.78-cm stainless steel bar stock. The cover was held in place by the counterforce applied between the hook and plate by the spring-loaded mechanism. The spring-loaded mechanism prevents monkeys from removing the cover. When the cover is in place, it forms a barrier between the shavings and the drain. The drain cover lies beneath the shavings and remains in place at all times except when shavings have been removed and cleaning or disinfecting with water takes place (see Procedure).

Figure 1.

(A) Device used to cover the drains in each animal pen. The device was constructed from high-density polyethylene and (B) attached to the gate of the drain with a spring loaded-T-hook mechanism made of stainless steel bar stock. (C) The drain cover fit flush against the drain and (D) prevented shavings from entering the drain.

Shavings.

Wood shavings (lab grade pine; NEPCO, Warrensburg, NY) were used to cover the indoor pen floors to a depth of roughly 5 cm (Figures 1 and 2). Approximately 0.15 yd³ (1/3 to 1/2 bag) of shavings was used per pen (0.4 m × 2.4 m × 2.7 m). The number of bags of shavings used was based on trial, evaluation, and observation to determine the quantity needed to achieve the overall aim of providing sufficient substrate to cover the floor, create foraging opportunities, and maintain cleanliness. Soiled shavings were removed daily and were replaced as needed with supplementary clean shavings. The facility manager developed guidelines and instructed carestaff on the process for daily examination, removal, and replacement of soiled shavings. The guidelines provided were to remove shavings with a scoop if they were visibly wet and to remove shavings and chow with a basket fork if there was an abundance of chow visibly soiled by feces. Clean shavings were then added in a volume roughly equally to the amount removed.

Figure 2.

Adolescent male bonnet macaque exploring wood shavings on the floor of his indoor pen housing environment.

Procedure.

An overview of the study design is shown in Figure 3. The study took place at the Wake Forest University Health Sciences Friedberg Campus from February 2009 through November 2009. In brief, the first phase of the study included a 2-wk baseline data collection period to determine the actual cost of husbandry with the bare pen floors. A brief pilot study then was conducted with a subset of pens to evaluate the success of drain covers in preventing shavings from entering the water pipes. The second phase of the study began with placement of drain covers and wood shavings in the indoor area of all pens. The initial 4 wk after initiation of wood shavings as a floor covering served as a period in which to evaluate and adjust husbandry-related procedures. After that period, labor and cost data were collected for 2 wk by using the same method as at baseline, to provide direct comparison of labor costs associated with bare floors compared with those of floors covered with bedding.

Figure 3.

Overall study design and husbandry procedures.

Husbandry.

The cleaning and waste removal procedure used for pens with bare floors included daily cleaning with water and chemical disinfection once each week. To accomplish this end, all animals within an indoor:outdoor pen were moved to 1 of their 2 enclosures while animal care staff cleaned the other. After provision of wood shaving bedding, cleaning procedures were modified to replace daily indoor water cleaning with spot-cleaning to remove soiled shavings and replace them with clean bedding. The majority of the shavings were removed by shoveling, sweeping, and scooping. The animal care personnel were diligent about removing the shavings and, as a result, only infrequent small particles of shavings were washed down the drains. Compliance was high, because the staff understood that if the shavings were removed thoroughly prior to opening of the drain-covers, work would not be interrupted by clogged drains.

During the initial 8 wk, chemical disinfection with concurrent full removal of soiled shavings occurred once weekly; however, the husbandry procedure was refined further after observation that pens remained clean, and weekly removal of shavings and disinfect was deemed unnecessary. The absolute frequency of cleaning and disinfecting are not specified by regulation, rather they are at the discretion of the attending veterinarian and are guided by professional judgment of cleanliness. The evaluator of cleanliness and guide for our decision-making was our facility Operations Manager (VAH), who is a Certified Manager of Animal Resources (CMAR) and Registered Laboratory Animal Technologist (RLATG) and who has extensive experience in our facility, including work with animal care and research, as well as many years in her supervisory position. We also relied on evaluation by care and research staff, who visually inspected the area and monitored odor. Upon observation that daily spot-cleaning was sufficient to maintain acceptable levels of cleanliness for a 2-wk period, the frequency of removal and replacement of all shavings, along with chemical disinfection, was changed from weekly to every 2 wk. Continued observation confirmed that pens were maintained at acceptable levels of cleanliness under this schedule.

Cost calculations.

Cost analysis was divided into 2 major categories: initial costs for implementing the provision of shavings and annual costs related to husbandry. All costs were evaluated, including materials (drain covers, cleaning equipment, storage equipment), consumable supplies (shavings, chemicals, water), and labor. The amount of time required for husbandry was assessed by using a method the Friedberg Campus Operations Manager (VAH) developed previously. Direct labor time studies were conducted to determine the amount of time needed to provide husbandry care for one monkey daily. Actual labor time was recorded by each animal care staff member performing any husbandry task in the animal area under study. Start and stop times were recorded in a log placed next to a clock in the anteroom of the animal area. The total number of minutes of labor then was calculated from these logs by the facility manager at the end of the study period. Studies were conducted for 14-d time periods so that all activities involved in a specific animal area were accounted for, including those that occurred daily, weekly, and biweekly. Activities included observations, cleaning, disinfecting, feeding, weighing food, and any other tasks that pertained to the housing area and the monkeys occupying the space.

Data analysis.

The goal of the study was to provide as comprehensive an evaluation as possible of the cost of providing wood shavings to pen-housed monkeys. Therefore our analysis was based on actual costs of initial infrastructure changes, materials, supplies, and labor. For the purposes of broad comparison, however, we transformed much of the raw data to percentages of baseline values to compare bare pen and bedding husbandry costs. Data are shown in summary, with increases in costs shown as positive values and decreased costs as negative values.

Direct labor data were analyzed according to the standard method developed by the Operations Manager, as follows. Total husbandry time for an animal housing area was averaged across a 14-d period and divided by the number of monkeys housed to yield the number of minutes it took care for a single monkey per day in that specific area. Labor costs were calculated by using the average salary plus fringe benefits of existing animal care staff. These data then were transformed to percentage of the baseline labor required for husbandry.

Results

The provision of wood shavings resulted in no adverse effects to animals, personnel, the housing facility, or ongoing research. During the 8 mo in which shavings have been in place, we have observed no flooding, drain blockage, clinical issues resulting from shavings, or staff injuries due to the changes in husbandry procedures. A summary of all costs is shown as the percentage change from the baseline cost of husbandry with bare pen floors (Table 1).

Table 1.

Husbandry costs, water usage and costs, and chemical usage associated with disinfecting pens weekly and biweekly

	Percentage change from baseline value (no shavings)
	Disinfect weekly	Disinfect biweekly
Husbandry and labor cost	−1%	−22%
Water usage and cost	−43%	−56%
Disinfecting chemical usage and cost	0%	−50%
Total cost increase
First year (including start-up costs)	12%	−9%
Subsequent years	7%	−14%

Negative values indicate cost savings

Initial costs.

The cost of equipment needed to protect the drain system from clogging by shavings (drain covers) and for provision, storage, and removal of shavings (that is, shovels, waste receptacles) from pens comprised the total initial investment (USD$1356).

Husbandry labor.

Table 1 provides a summary of the decrease in husbandry time that accompanied the addition of wood shavings to the pen floors. Labor time was relatively stable with the addition of wood shavings as compared with time required for husbandry with bare floors, decreasing only 1% when disinfection frequency was unchanged. One of the advantages of using wood shavings, however, was that the frequency of disinfection could be decreased without negatively affecting the cleanliness of the animals' pens. Therefore, the frequency of disinfection, a process that is both highly laborious as well as disruptive to the animals,¹³ could be decreased to occur every other week. As a result, labor time was reduced by 22% from the baseline time required for husbandry with bare floors.

Other costs.

The predominant cost of providing bedding for the monkeys' floors was the bedding itself. Other leading components of husbandry-related costs were associated with cleaning, including waste removal, water, and cleaning chemicals. These costs were included in our overall analysis by adding the annual cost of wood shavings (USD$2825) based on the volume used during the study period; the fraction of the overall facility waste disposal fee attributable to the estimated annual volume of shavings used in the building (USD$310); the estimated number of gallons of water (192,000 gal) saved by reducing the frequency of water used in cleaning; and the estimated volume of chemicals saved by reducing the frequency of disinfection. Reduction in chemical use over an annual period is estimated to include 9.75 gal Iodex (iodine and phosphoric acid mixture; Quip Laboratory Supply, Wilmington, DE), 6.50 gal Chlordet (potassium hydroxide mixture; Quip Laboratory Supply), and 52 gal household bleach.

Discussion

Provision of wood shavings on the floors of pens housing bonnet macaques resulted in overall cost savings of roughly 14% annually, with the increased cost for initial materials and ongoing cost of consumable supplies (shavings) negated by cost savings in labor, water, and cleaning chemicals. We calculated that the decreased labor, water, and chemical costs during the first year would result not only in total cost recovery for the initial investment in materials and equipment but also an additional 9% decrease in husbandry-associated cost.

Overall, the results of this study demonstrate that provision of wood shavings as bedding material for pen-housed monkeys is a cost-effective environmental enhancement strategy. No adverse events to monkeys, personnel, ongoing research, or facilities occurred. After an extended evaluation period (8 mo), monkeys housed with bedding have exhibited no observable negative health consequences related to the bedding. Neither have we observed any problems with flooding due to clogged lixits or evidence of drain blockage due to accrual of shavings in the water pipes. Anecdotally, we have observed improvements in the coat quality of several animals that had previously shown mild alopecia. Animal carestaff have responded favorably to the change in husbandry and have expressed positive perceptions of the effect of bedding on animals' wellbeing. Furthermore, no staff injuries or increased exposure to potential pathogens have been noted.

A long-standing body of literature documents the beneficial effects of bedding for the welfare of laboratory-housed nonhuman primates.^4-6,8,9,15 Our study did not attempt to measure welfare benefit but instead focused on careful analysis of pragmatic and cost issues that can stand as obstacles to implementing this environmental enhancement. When viewed within the context of the previous literature, however, the current study demonstrates that the welfare benefits reported by others as a result of providing bedding to monkeys can be accompanied by lower husbandry costs than those incurred with bare floors. In turn, joint consideration of these results supports the conclusion that provision of wood shavings results in substantial benefit in terms of both animal welfare and cost. Direct comparison of the relative cost and benefit of different environmental enrichment strategies is difficult in absence of comprehensive, meaningful, and widely accepted standard metrics for comparison. Nonetheless, provision of bedding can reasonably be assigned high value from a cost–benefit perspective because it is the type of structural environmental enhancement strategy that can result in long-lasting benefits in multiple domains (animal welfare, labor, environmental) along with a modest reduction in overall husbandry costs. Furthermore, the results of the current study illustrate one method for explicitly including cost calculation in studies that aim to assist in comparison, evaluation, and identification of effective enrichment strategies.

In addition, the results of our study demonstrate the effectiveness of an engineering solution to the potential challenge wood shavings pose in terms of clogging water pipes. Nonhuman primate facilities differ greatly in structure and, therefore, the system we used may not be feasible in other facilities. The net cost and disruption resulting from clogged drains and water pipes in animal housing areas can be substantial. As a result, most facilities proceed with appropriate caution when considering environmental enrichment and enhancement strategies that increase the volume of material with potential to enter the drainage system. The system we used here demonstrates, however, that combining an engineering solution and modification of husbandry procedures may provide a successful avenue for provision of wood shavings without harm to the housing environment. In fact, other nonhuman primate research facilities have had similar success in using various drain cover systems for pen-housed monkeys provided with bedding.¹⁰

One of the successful outcomes of this study was a reduction in water and chemicals used for cleaning the animal housing area. As demonstrated in previous studies,^8,9,18 the use of wood shavings as bedding markedly reduced the need for daily cleaning with a high volume of water and weekly chemical disinfection. The resulting savings in terms of chemical and water costs are obvious; less obvious are the benefits to animal welfare, personnel safety, and the environment. The changes in husbandry procedures meant that animals experienced less daily disruption due to cleaning and husbandry tasks that required the animals to be confined to only one portion of their indoor:outdoor pens. The change in husbandry also may have benefitted animal carestaff. Our carestaff are equipped with appropriate personnel protective devices and with excellent safety training that together minimize risk of injury and exposure to pathogens regardless of the type or frequency of cleaning activities. Nonetheless all such activities result in some safety risk. Although we were not able to collect quantitative data on exposure risk to carestaff, we suspect that the potential pathogen exposure and overall risk may be reduced by the provision of bedding and by reduced frequency of cleaning with pressurized water. Pressurized water cleaning increases the risk of exposure to aerosolized pathogens, falls on wet surfaces, and repetitive-motion injuries from using the water hoses. Therefore, reducing the frequency of pressurized water cleaning may reduce overall risk to personnel safety. Addition of bedding could have resulted in increased safety risks, including injuries due to shoveling shavings to remove them from cages. However, we considered this possibility carefully at the outset and designed standard operating procedures for cleaning that included ergonomic equipment and practices to minimize risk.

Environmental benefits included not only an estimated annual savings of 192,000 gal water but also a reduction in chemicals (bleach, iodine, phosphoric acid, potassium hydroxide) that ultimately enter the waste stream. Although beyond the study reported here, these initial data suggest that one area for productive future exploration is analysis of the sustainability and ‘green’ costs and benefits related modification of husbandry procedures in laboratory animal housing facilities. In addition, such analysis could include more thorough investigation of related animal health considerations.

Part of the core intent of this project was to build a method and procedures for using a team-based approach to implement and evaluate strategies for enhancement of laboratory animal welfare. The team-based approach included representatives from each of the multiple personnel divisions (research, enrichment, care staff, veterinary, administrative) involved in laboratory animal care and its oversight. Although these divisions share common overall goals, each has different responsibilities and different concerns, perspectives, and expertise. The importance of incorporating contributions from a team comprising members of each division is that the approach then is better able to generate a comprehensive cost–benefit analysis inclusive of all considerations that hold influence in the evaluation, implementation, and potential success of an intervention aimed at improving animal welfare. As a result, the potential sustainability, long-term success, personnel, and institutional support for a particular environmental enhancement strategy is strengthened.

One of the challenges to consensus and team-building lies in definition of the project goals and the metric for evaluation of its success. The aims of the study reported here were defined in a manner that could be addressed with objective measures to provide information essential to facility management and to considered decisions about an environmental enhancement strategy that would have broad effect not only on the animals but also on engineering and husbandry staff and budget. Therefore, we did not focus primarily on the animals' behavioral response to provision of bedding but rather on conducting empirical evaluation of perceived obstacles, costs, and benefits. As a result, we were able to demonstrate clearly that use of wood shavings as bedding and foraging substrate for pen-housed monkeys reduces costs and does not result in any adverse effects for any of the stakeholders or divisions involved in animal care, research, or oversight. In turn, the data provided the requisite foundation for extension of this environmental enhancement technique to other animal housing buildings, and they likely will provide useful information to other facilities with similar concerns and interests.

Accepted professional standards for evidence-based evaluation of environmental enrichment and other strategies for laboratory animal welfare improvement have emerged from several decades of extensive studies whose outcome measures include aspects of animals' behavior and physiology.^2,17 By contrast, professional standards for analysis of other important factors that ultimately influence decision-making and implementation of animal welfare improvements have yet to be clearly defined, widely accepted, or consistently applied.^3,14 The study reported here illustrates one successful avenue for moving toward an evidence-based cost–benefit analysis of environmental enrichment and enhancement strategies. Continued emphasis on rigorous evaluation and objective measures of cost and benefit, as well as more comprehensive inclusion of the many factors and team members involved in laboratory animal studies, holds strong potential for building a better foundation from which to contribute effective changes and improvements in laboratory animal welfare.