筑巢材料在实验大、小鼠环境丰荣中的应用

相对于标准鼠盒,实验大、小鼠更喜好有筑巢材料的“环境丰荣”鼠盒.向标准鼠盒中放入筑巢材料,可以为大、小鼠提供筑巢、躲避、攀爬、休息的环境.因此,在实验大、小鼠饲养过程中,提供筑巢材料,是一个简单有效的丰富实验动物环境,提高实验动物福利的方法.本文就筑巢材料应用背景、近年来在啮齿类实验动物环境丰荣中的应用、对实验动物福利的影响三方面做以综述,并对今后筑巢材料在改善实验动物福利的应用前景作以展望.     

Preference for social contact versus environmental enrichment in male laboratory mice

Due to their aggressive nature, male mice are less frequently used than female mice in biomedical research. When aggressive males are being used, individual housing is common practice. The question arises whether this is an acceptable housing for a social species. The present study was designed to gain more insight into the nature of inter-male social contact and into the potential of a form of environmental enrichment (nesting material) to compensate for the lack of social contact. In a series of tests, we analysed whether male mice of different ages preferred to spend time (1) near a familiar cage mate versus an empty cage, or (2) near to a familiar cage mate versus direct contact with nesting material (tissues). Dwelling time in each of the test cages and sleeping sites was recorded, as was the behaviour of the test mice. Results indicated that when other conditions were similar, male mice preferred to sleep in close proximity to their familiar cage mate. Furthermore, the need to engage in active social behaviour increased with age. Tissues were used to a large extent for sleeping and sleep-related behaviour. It is concluded that single housing in order to avoid aggression between male mice is a solution with evident negative consequences for the animals. When individual housing is inevitable due to excessive aggressive behaviour, the presence of nesting material could partly compensate for the deprivation of social contact.     

A targeted approach to developing environmental enrichment for two strains of laboratory mice

Previous studies on environmental enrichment have generally placed a purported enrichment in the cage and observed changes in behavioural and physiological indicators of welfare. However, many of these ‘enrichments’ are not purposely designed, or appear to be designed with anthropomorphic or anthropocentric concerns, which have little biological relevance. The aim of this study was to screen the behavioural responses of mice to a range of 24 potential enrichments (PEs) considered by an expert panel to have characteristics most biologically relevant to mice. Female mice (64 C57/Bl/6 and 64 ICR(CD-1)) were housed in groups of four and observed three days per week for 12 weeks whilst provided with a different PE weekly. The overall time-budgets of the two strains differed significantly. ICR(CD-1) mice performed more bar chewing, digging, manipulation of PEs, and rearing in the cage. They were also more likely to be hidden in the cage. C57/Bl/6 mice performed more drinking, cage sniffing and social interaction, and showed three times more bar climbing. The two strains responded differently to the PEs, with the ICR(CD-1) mice making more use of PEs, particularly those that could be manipulated or which provided additional hiding places. The higher trait anxiety of the C57/Bl/6 mice may have reduced their utilisation of novel PEs. We conclude that, whilst enrichment can significantly improve animal welfare, those types of enrichments that work well for all strains need to be identified, or strain-specific enrichment policies devised.     

Effects of space allocation and housing density on measures of wellbeing in laboratory mice: a review

In the majority of countries where there are legislative requirements pertaining to the use of animals in research, figures are quoted for minimum cage sizes or space allocation to be provided per animal. These figures are generally based on professional judgement and are in common usage. However, there is a growing trend and expectation that welfare science should inform regulatory decision-making. Given the importance of the potential welfare influences of cage size on the animals themselves, this paper presents the latest scientific knowledge on this topic in one of the most commonly used animals in research, the mouse. A comprehensive review of studies in laboratory mice was undertaken, examining the effects of space allocation per animal and animal density on established welfare indicators. To date, animal density studies have predominated, and the effects of space allocation per se are still relatively unclear. This information will guide those involved in facility management or legislative review, and provide a more solid foundation for further studies into the effects of routine husbandry practices on animal welfare.     

Impact of environmental enrichment in mice. 1: effect of housing conditions on body weight,organ weights and haematology in different strains

Currently, environmental enrichment is a very common means of improving animal well-being, especially for laboratory animals. Although environmental enrichment seems to be a possible way for improving the well-being of animals, the consideration of housing laboratory animals should not only focus solely on animal well-being, manpower and economics but also on the precision and accuracy of the experimental results. The purpose of the present study was to evaluate the effects of enriched cages (nest box, nesting material, climbing bar) on body weight, haematological data and final organ weights. BALB/c, C57BL/6 and A/J mice, originated from Harlan Winkelmann, were used for the experiments - 16 animals of each strain. Animals at 3 weeks of age were marked and separated randomly to enriched or non-enriched cages, in groups of four, half for each housing condition. Both cages were type III Makrolon cages, only the enriched cages contained a nest box, a wood bar for climbing and nesting material. Animals were kept in a clean animal room under specific pathogen free (SPF) conditions. Body weights were recorded every week. Blood samples were collected at 14 weeks of age (white blood cells (WBC), red blood cells (RBC), haemoglobin (HGB), and haematocrit (HCT) were analysed). At 15 weeks of age, the animals were euthanized by CO(2) in their home cages, and final body weight and organ weights (heart, liver, kidney, adrenal, spleen and uterus) were recorded immediately. Although nearly all the test variables were not affected by environmental enrichment in their mean values, the enriched group showed higher coefficients of variation in many variables, and strain differences of both housing conditions were not consistent. The influences of enrichment were shown to be strain- and test-dependent. Such effects may lead to an increase in the number of animals which is necessary or may change the experimental results, especially when a study, using enriched housing conditions, focuses on strain differences. Since the same enrichment design can result in different influences, a positive or a negative or no adverse effect, due to the strain and the variables studied, researchers need to collect more information before enrichment designs are introduced into experimental plans.     

Comparison of survival rates in four inbred mouse strains under different housing conditions: effects of environmental enrichment

Housing conditions can affect the well-being of laboratory animals and thereby affect the outcomes of experiments. The appropriate environment is essential for the expression of natural behavior in animals. Here, we compared survival rates in four inbred mouse strains maintained under three different environmental conditions. Three mouse strains (C57BL/6J, C3H/HeN, and DBA/2J) housed under environmental enrichment (EE) conditions showed improved survival; however, EE did not alter the survival rate of the fourth strain, BALB/c. None of the strains showed significant differences in body weights or plasma corticosterone levels in the three environmental conditions. For BALB/c mice, the rates of debility were higher in the EE group. Interestingly, for C57BL/6J and C3H/HeN mice, the incidence of animals with alopecia was significantly lower in the EE groups than in the control group. It is possible that the enriched environment provided greater opportunities for sheltering in a secure location in which to avoid interactions with other mice. The cloth mat flooring used for the EE group was bitten and chewed by the mice. Our findings suggest that depending on the mouse strains different responses to EE are caused with regard to health and survival rates. The results of this study provide basic data for further studies on EE.     

Behaviour of laboratory mice in different housing conditions when allowed to self-administer an anxiolytic

Standard cages prevent mice from performing several natural behaviours for which they are motivated. As a consequence, abnormal behaviours sometimes develop and mice often spend long periods inactive. To improve welfare, cages are sometimes furnished with items such as nesting material, shelters and running wheels. We have previously reported that when allowed to self-administer an anxiolytic, mice in furnished cages consume less anxiolytic than mice in standard cages. This paper presents the results of behaviour studies of the mice in the same experiment. Female C57BL/6J mice (3 per cage) were housed in Standard (n = 10), Unpredictable (n = 10) or Furnished (n = 6) cages. Unpredictable cages were identical to Standard cages, but were exposed to unpredictable events two to three times a week. Furnished cages were double the size of Standard cages and contained nesting material, nest box, tubes, chew blocks and a running wheel. During three consecutive periods, mice had access to only water (control), water or an anxiolytic solution on a daily alternating schedule (forced consumption), and finally, both water and anxiolytic (self-administration). Behaviour was analysed from video recordings taken during the dark phase. The housing type affected behaviour both under the control and the self-administration conditions. Overall, mice in Furnished cages spent less time resting and performing bar-related behaviours and more time on exploratory/locomotory behaviours. Mice in Furnished cages also performed less bar-circling stereotypies than mice in Standard cages. The Unpredictable treatment did not significantly affect behaviour compared to mice in the Standard conditions. There was an overall effect of anxiolytic availability on rest-related behaviours and on exploration-locomotion behaviours, in that mice rested more and spent less time on exploration and locomotion when they were able to self-administer the anxiolytic.     

Effects of environmental enrichment for mice: variation in experimental results

This study focused on the effects of different enriched environments for mice in a number of behavioral and physiological parameters in 2 routine laboratory testing procedures: potency testing for tetanus vaccine and stress-induced hyperthermia. The variability in the results was studied by calculating and analyzing mean absolute deviations. Mice from enriched conditions weighed more and consumed more food than mice from standard housing conditions. However, mice from enriched conditions lost more body weight after being housed individually. Other physiological parameters showed no differences. Mice from standard conditions were more active in an open field, suggesting a tendency to overrespond to various stimuli in a testing environment. Mice from enriched environments were more tranquil and easier to handle. The enrichment did not influence the variability in any of the parameters measured, although earlier results and results of other studies suggest that the effects on the variability in results are parameter dependent. When enrichment does not influence variability, there is no reason for not introducing cage enrichment and by doing so contributing to the animals' welfare.     

Mandatory " enriched" housing of laboratory animals: the need for evidence-based evaluation

Environmental enrichment for laboratory animals has come to be viewed as a potential method for improving animal well-being in addition to its original sense as a paradigm for learning how experience molds the brain. It is suggested that the term housing supplementation better describes the wide range of alterations to laboratory animal housing that has been proposed or investigated. Changes in the environments of animals have important effects on brain structure, physiology, and behavior--including recovery from illness and injury--and on which genes are expressed in various organs. Studies are reviewed that show how the brain and other organs respond to environmental change. These data warrant caution that minor cage supplementation intended for improvement of animal well-being may alter important aspects of an animal's physiology and development in a manner not easily predicted from available research. Thus, various forms of housing supplementation, although utilized or even preferred by the animals, may not enhance laboratory animal well-being and may be detrimental to the research for which the laboratory animals are used.     

Potential for unintended consequences of environmental enrichment for laboratory animals and research results

Many aspects of the research animal's housing environment are controlled for quality and/or standardization. Of recent interest is the potential for environmental enrichment to have unexpected consequences such as unintended harm to the animal, or the introduction of variability into a study that may confound the experimental data. The effects of enrichment provided to nonhuman primates, rodents, and rabbits are described to illustrate that the effects can be numerous and may vary by strain and/or species. Examples of parameters measured where no change is detected are also included because this information provides an important counterpoint to studies that demonstrate an effect. In addition, this review of effects and noneffects serves as a reminder that the provision of enrichment should be evaluated in the context of the health of the animal and research goals on a case-by-case basis. It should also be kept in mind that the effects produced by enrichment are similar to those of other components of the animal's environment. Although it is unlikely that every possible environmental variable can be controlled both within and among research institutions, more detailed disclosure of the living environment of the subject animals in publications will allow for a better comparison of the findings and contribute to the broader knowledge base of the effects of enrichment.     

Modifications to husbandry and housing conditions of laboratory rodents for improved well-being

For a change to be considered enriching, the change must enhance animal welfare and improve biological functioning of the animals. A review of the literature shows that a consensus on the definition of changes constituting "environmental enrichment" has yet to be reached. For this reason, the results of studies on the effects of rodent enrichment are inconsistent. In many cases, changes have not been shown to be real improvements. However, enrichment is increasingly appreciated as a way to improve the well-being of rodents, providing them with opportunities for species-specific behaviors that might be available to them in the wild. Frequently defined as "change to the environment," enrichment can be as complex as devices (frequently termed "toys") or as simple as the provision of tissues from which mice readily construct nests. Nest making is a learned behavior in rats, and laboratory rats do show preferences for chewable objects in their environment. Rather than attempting a comprehensive review of the entire literature on environmental enrichment and its effects on rodent physiology and behavior, this paper focuses on husbandry and housing alterations that may improve the welfare of laboratory rodents. The effects of beneficial changes in housing and husbandry on rodent well-being and on experimental variability--and thus cost--are discussed. Areas that require more research are suggested. Also suggested are possible inexpensive and effective enrichment schemes for laboratory mice that might include reducing the cage floor space per mouse combined with providing nesting material.     

A review of environmental enrichment for kennelled dogs,Canis familiaris

Domestic dogs can be housed in a variety of confined conditions, including kennels, shelters and laboratories. Concern over the well-being of dogs housed in human care has prompted much research in recent years into the enrichment of environments for kennelled dogs. This paper highlights the findings and recommendations arising from this work. Two types of general enrichment method are discussed, namely animate (i.e. enrichment through the provision of social contacts with conspecifics and humans) and inanimate (i.e. enrichment through the provision of toys, cage furniture, auditory and olfactory stimulation). The benefits and, where relevant, possible disadvantages, to these various types of enrichment method are highlighted throughout.     

Environmental enrichment for laboratory rodents

Modernization of housing and husbandry techniques for rodents has minimized confounding variables. The result has been vastly improved health maintenance and reproducibility of research findings, advances that have decreased the numbers of animals needed to attain statistically significant results. Even though not all aspects of rodent manipulation have been strictly defined, as housing and handling procedures have become increasingly standardized, many animal care personnel have recognized the lack of complexity of the rodents' environment. Concern for this aspect of animal well-being has led many research facilities to provide "environmental enrichment" for rodents. Additionally, regulatory agencies in the United States and Europe have also been increasingly concerned about this issue relative to laboratory animal husbandry. However, little is known about the influence such husbandry modifications may have on biological parameters. In this article, laws and guidelines relating to rodent enrichment are reviewed, the natural behaviors of select rodent species are discussed, and an overview of widely used types of enrichment in laboratory rodent management is provided. The literature evaluating effects of rodent enrichment is reviewed both in terms of neurological development and as an experimental variable, and results of a study evaluating the effect of enrichment on immune and physiological parameters are reported. Survey data on current enrichment practices in a large multi-institutional organization are presented, and practical aspects requiring consideration when devising a rodent enrichment program are discussed.     

Environmental enrichment for laboratory marmosets

The authors report on using two environmental enrichment devices for marmosets, and suggest the design of five other devices that may be more successful in stimulating foraging or grooming behavior than the devices tested.     

Improved laboratory enrichment for enterohemorrhagic Escherichia coli by exposure to extremely acidic conditions

Analysis of food samples for E. coli O157:H7 using the standard U.S. Food and Drug Administration procedure is frequently complicated by overgrowth of nontarget microorganisms. A new procedure was developed for enrichment of enterohemorrhagic E. coli (EHEC) which utilizes exposure to pH 2.00 for 2 h. This procedure yielded larger populations of EHEC than the standard method by factors ranging from 2.7 to 7.7 and, when age-stressed cultures were used, by factors ranging from 2.7 to 11.5. Cultures of competing enterics were more effectively inhibited by the new enrichment protocol as well.     

Competition for limited environmental resources on the social dominance model in laboratory mice

Asymmetry of social rank in the competition for food and female was studied using the social dominance model with only two male mice. Marking activity was recorded as a useful indicator of the social status. Social rank was determined by asymmetry in aggressive behavior. A food test was presented for 10 min daily within 5 days of the experiment, whereas a sexual test was performed only on the 5th day for 30 min. Marking behavior was estimated twice: before the first interaction and on the 4th day of the experiment. The competition for food was accompanied by active attacks, escapes, vertical defense postures, and sniffing. The level of aggression, sniffing, and food activity was higher in dominant than submissive males. Time course of aggressive, defensive, and sniffing behaviors was characterized by maximum scores in the period of formation of social hierarchy; however, the rate of food activity in this period was low and increased only to the 4th day. Introduction of a receptive female into the male group with the stable social hierarchy stimulated the intermale aggression, defensive and sniffing behaviors. Dominant males were characterized by a greater number of victories over and sniffing contacts with both male and female. Marking activity was also more intense in dominants. Thus, significant unidirectional rank differences in agonistic, sniffing, food, sexual, and marking behaviors were shown on the social dominance model with the minimum number of partners.     

Behavioral assessment of intermittent wheel running and individual housing in mice in the laboratory

Physical cage enrichment—exercise devices for rodents in the laboratory—often includes running wheels. This study compared responses of mice in enriched physical and social conditions and in standard social conditions to wheel running, individual housing, and open-field test. The study divided into 6 groups, 48 female BALB/c mice group housed in enriched and standard conditions. On alternate days, the study exposed 2 groups to individual running wheel cages. It intermittently separated from their cage mates and housed individually 2 groups with no running wheels; 2 control groups remained in enriched or standard condition cages. There were no significant differences between enriched and standard group housed mice in alternate days' wheel running. Over time, enriched, group housed mice ran less. Both groups responded similarly to individual housing. In open-field test, mice exposed to individual housing without running wheel moved more and faster than wheel running and home cage control mice. They have lower body weights than group housed and wheel running mice. Intermittent withdrawal of individual housing affects the animals more than other commodities. Wheel running normalizes some effects of intermittent separation from the enriched, social home cage.     

USDA perspective on environmental enrichment for animals

This article provides a brief historical background of the events and circumstances that led to the 1985 Animal Welfare Act (AWA) amendments. It describes the development of the regulations promulgated by the US Department of Agriculture (USDA) in 1991 as a result of these amendments, the reasoning given for the proposals, and the revisions that were made during the process. Information is included on USDA implementation of the regulations regarding exercise for dogs and environmental enhancement for nonhuman primates. Also mentioned briefly are the requirements for socialization of marine mammals and space requirements for certain other regulated warm-blooded species. These requirements apply to animal dealers (breeders and brokers), exhibitors, commercial transporters, and research facilities. The standards for exercise and environmental enhancement were different from any others previously contained in the AWA regulations, and required more research and understanding of species-specific needs by the regulated community. Finally, this article describes some of the initiatives being undertaken by the research community and USDA-Animal and Plant Health Inspection Services (APHIS)-Animal Care to provide the necessary education and guidance indicated by the violation history data.