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.     

The influence of environmental enrichment on Chinese visitor behavior

Welfare improvements for nonhuman animals should aim to satisfy the needs of visitors as well as those of the animals. Little research has been conducted, however, and existing work is confined to zoos in developed countries. This article reports the behavioral responses of Chinese visitors to environmental enrichment improvements in a zoo enclosure. Visit, viewing, and stopping behaviors significantly increased at the transformed exhibit, indicating that it provoked greater visitor interest. Furthermore, increased intragroup behaviors suggested that the exhibit probably motivated visitors to interact socially. The positive impact of the exhibit changes supports the enrichment efforts taking place in zoos around the world. The changes also provide encouragement for zoos in developing countries such as China because greater visitor interest provides a strong argument and an incentive for improving welfare standards.     

Assessing the effectiveness of environmental enrichment in bottlenose dolphins (Tursiops truncatus)

Environmental enrichment is often used to improve well-being and reduce stereotyped behaviors in animals under human care. However, the use of objects to enrich animal environments should not be considered to be effective until its success has been scientifically demonstrated. This study was conducted at Asterix Park in France in April 2009. The study investigated the use of 21 familiar objects with a group of six bottlenose dolphins (Tursiops truncatus). The dolphin trainers introduced four different objects into the dolphin pool every day on a rotating basis. Using a focal-object sampling method, we collected and analyzed data from twenty-one 15 min sessions. The results revealed a positive correlation between interest behaviors and interactive behaviors. Some dolphins had "favorite toys". However, only 50% of objects elicited manipulative behaviors. These findings demonstrate that dolphins do not treat all objects provided to them as "toys". Behavioral changes in the animals subsequent to the introduction of objects do not necessarily indicate an enrichment effect of the objects; rather, the motivation for the dolphins' behaviors toward the objects must be investigated. The animals' behavior must be considered in light of the social context and of the animals' individual behavioral profiles. The relevance of a constructivist approach to evaluating the effectiveness of enrichment programs is discussed.     

Comparative analysis of metagenomes from three methanogenic hydrocarbon-degrading enrichment cultures with 41 environmental samples

Methanogenic hydrocarbon metabolism is a key process in subsurface oil reservoirs and hydrocarbon-contaminated environments and thus warrants greater understanding to improve current technologies for fossil fuel extraction and bioremediation. In this study, three hydrocarbon-degrading methanogenic cultures established from two geographically distinct environments and incubated with different hydrocarbon substrates (added as single hydrocarbons or as mixtures) were subjected to metagenomic and 16S rRNA gene pyrosequencing to test whether these differences affect the genetic potential and composition of the communities. Enrichment of different putative hydrocarbon-degrading bacteria in each culture appeared to be substrate dependent, though all cultures contained both acetate- and H₂-utilizing methanogens. Despite differing hydrocarbon substrates and inoculum sources, all three cultures harbored genes for hydrocarbon activation by fumarate addition (bssA, assA, nmsA) and carboxylation (abcA, ancA), along with those for associated downstream pathways (bbs, bcr, bam), though the cultures incubated with hydrocarbon mixtures contained a broader diversity of fumarate addition genes. A comparative metagenomic analysis of the three cultures showed that they were functionally redundant despite their enrichment backgrounds, sharing multiple features associated with syntrophic hydrocarbon conversion to methane. In addition, a comparative analysis of the culture metagenomes with those of 41 environmental samples (containing varying proportions of methanogens) showed that the three cultures were functionally most similar to each other but distinct from other environments, including hydrocarbon-impacted environments (for example, oil sands tailings ponds and oil-affected marine sediments). This study provides a basis for understanding key functions and environmental selection in methanogenic hydrocarbon-associated communities.     

Neural consequences of environmental enrichment

Neuronal plasticity is a central theme of modern neurobiology, from cellular and molecular mechanisms of synapse formation in Drosophila to behavioural recovery from strokes in elderly humans. Although the methods used to measure plastic responses differ, the stimuli required to elicit plasticity are thought to be activity-dependent. In this article, we focus on the neuronal changes that occur in response to complex stimulation by an enriched environment. We emphasize the behavioural and neurobiological consequences of specific elements of enrichment, especially exercise and learning.     

Impact of social stress during gestation and environmental enrichment during lactation on the maternal behavior of sows

The impact of a social stress in gestation and an enriched pen in lactation on components of sow maternal behavior was studied in a 2 × 2 factorial experiment. At breeding, 41 sows were assigned to a social mixing stress treatment (T) during mid-gestation or a control group (C). During lactation, half of the T and C sows were housed in straw enriched pens (E) (1.57 m × 4.10 m) and the others in standard farrowing crates (S) (0.68 m × 2.10 m). The mixing stress consisted in introducing each T sow to the home pen of two unfamiliar sows twice for 1 week, from d 39 to 45 and 59 to 65 of gestation. Aggressive behavior was observed and lesion scores were taken to confirm that a social stress occurred. During lactation, the responses of sows to a simulated piglet crush test on d 3 and an isolated piglet playback test on d 21 were observed. Postural budgets of sows were automatically detected using accelerometers on d 5 and 19 of lactation. Sow-initiated social contacts with the piglets were observed continuously from video recordings on d 6 and 20 of lactation. Data were analyzed with a mixed models procedure. The social stress treatment had an impact on the response of sows to isolated piglet vocalizations with T sows showing longer latencies to respond vocally than C sows (P = 0.035). In early lactation, T sows spent more time lying ventrally than C sows (P = 0.007). Furthermore, the social stress had an impact on the space use in the enriched housing, with T sows spending less time in the nesting straw area of the pen than C sows (P = 0.018). Housing also impacted maternal behavior with E sows tending to spend more time lying ventrally than S sows in late lactation (P = 0.067) and tending to have more social contacts with their piglets than S sows in early lactation (P = 0.058). In conclusion, the social stress during gestation had a slight negative impact on sow maternal behavior, and while an enriched farrowing pen allowed for more opportunities to express maternal behavior, it did not counteract the negative effects of gestation stress.     

Network enrichment analysis: extension of gene-set enrichment analysis to gene networks

ABSTRACT: BACKGROUND: Gene-set enrichment analyses (GEA or GSEA) are commonly used for biological characterization of an experimental gene-set. This is done by finding known functional categories, such as pathways or Gene Ontology terms, that are over-represented in the experimental set; the assessment is based on an overlap statistic. Rich biological information in terms of gene interaction network is now widely available, but this topological information is not used by GEA, so there is a need for methods that exploit this type of information in high-throughput data analysis. RESULTS: We developed a method of network enrichment analysis (NEA) that extends the overlap statistic in GEA to network links between genes in the experimental set and those in the functional categories. For the crucial step in statistical inference, we developed a fast network randomization algorithm in order to obtain the distribution of any network statistic under the null hypothesis of no association between an experimental gene-set and a functional category. We illustrate the NEA method using gene and protein expression data from a lung cancer study. CONCLUSIONS: The results indicate that the NEA method is more powerful than the traditional GEA, primarily because the relationships between gene sets were more strongly captured by network connectivity rather than by simple overlaps.     

Recovery of three arctic stream reaches from experimental nutrient enrichment

1. Nutrient enrichment and resulting eutrophication is a widespread anthropogenic influence on freshwater ecosystems, but recovery from nutrient enrichment is poorly understood, especially in stream environments. We examined multi‐year patterns in community recovery from experimental low‐concentration nutrient enrichment (N + P or P only) in three reaches of two Arctic tundra streams (Kuparuk River and Oksrukuyik Creek) on the North Slope of Alaska (U.S.A.). 2. Rates of recovery varied among community components and depended on duration of enrichment (2–13 consecutive growing seasons). Biomass of epilithic algae returned to reference levels rapidly (within 2 years), regardless of nutrients added or enrichment duration. Aquatic bryophyte cover, which increased greatly in the Kuparuk River only after long‐term enrichment (8 years), took 8 years of recovery to approach reference levels, after storms had scoured most remnant moss in the recovering reach. 3. Multi‐year persistence of bryophytes in the Kuparuk River appeared to prevent recovery of insect populations that had either been positively (e.g. the mayfly Ephemerella, most chironomid midge taxa) or negatively (e.g. the tube‐building chironomid Orthocladius rivulorum) affected by this shift in dominant primary producer. These lags in recovery (of >3 years) were probably driven by the persistent effect of bryophytes on physical benthic habitat. 4. Summer growth rates of Arctic grayling (both adults and young‐of‐year) in Oksrukuyik Creek (fertilised for 6 years with no bryophyte colonisation), which were consistently increased by nutrient addition, returned to reference rates within 1–2 years. 5. Rates of recovery of these virtually pristine Arctic stream ecosystems from low‐level nutrient enrichment appeared to be controlled largely by duration of enrichment, mediated through physical habitat shifts caused by eventual bryophyte colonisation, and subsequent physical disturbance that removed bryophytes. Nutrient enrichment of oligotrophic Arctic stream ecosystems caused by climate change or local anthropogenic activity may have dramatic and persistent consequences if it results in the colonisation of long‐lived primary producers that alter physical habitat.     

Effects of environmental enrichment on reproduction

Although there have been few demonstrations of a direct empirical relationship between environmental enrichment and reproductive success in captive animals, indirect and anecdotal evidence indicates the importance of physical and temporal complexity for reproduction. We discuss three major mechanisms through which environmental enrichment that specifically increases the complexity of an animal's surroundings may influence reproductive physiology and behavior: developmental processes, modulation of stress and arousal, and modification of social interactions. In complex environments developing animals learn that performing active behavior produces appropriate functional outcomes. Learning to control their environment influences their ability to adapt to novel situations, which may profoundly influence their reproductive behavior as adults in breeding situations. Chronic stress may compromise reproductive physiology and behavior; enrichment reduces stress by providing increased opportunity for behavioral coping responses. However, some degree of acute stress may be beneficial for reproduction by maintaining an animal's level of responsiveness to socio-sexual stimuli necessary for sexual arousal and reproductive activation. Finally, environmental enrichment may influence reproductive success by stabilizing social groups, reducing aggression and increasing affiliative and play behaviors. It is concluded that multi-variate multi-institutional behavioral research in zoos will play an increasingly important role in the successful captive propagation of many species by closely examining relationships between environmental variables and reproductive potential of individual animals. © 1994 Wiley-Liss, Inc.     

Cadmium stress studies: Media development, enrichment, consortia analysis, and environmental relevance

The effects of Cadmium (Cd) toxicity on bacterial consortia originating from an-aerobic sewage sludge and cultivated under differing enrichment conditions were studied. Cultures were enriched in minimal media developed specifically for Cd stress studies. At inoculation all Cd was soluble in free ion or chelated form. Electron donors and acceptors were varied to obtain each physiological enrichment type. Adaptation leading to higher levels of Cd resistance of the consortia over time was observed under all physiological conditions. Initial and increased Cd tolerances were consistently greatest in multiphysiological enrichments (MPH). Sulfate reducing (SRB), methanogenic (MET), and fermentative (FRM) enrichments had less tolerance however, the level of tolerance to the Cd varied from one inoculation to the next. The Cd remained soluble as free Cd in MPH and FRM conditions and was precipitated significantly in SRB and moderately in MET conditions. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified 16S rRNA of the SRB, MPH, and FRM enrichments were followed over time. The consortia underwent succession under all physiological conditions when compared with the profile of the inoculum. Microbial population diversity decreased as the consortia were subcultured. The effects of chelators in the MPH medium were also evaluated. The addition of chelators transiently decreased toxicity. Effects of MPH medium on the Cd sorption capacity of soil were evaluated. Microbial growth decreased the amount of Cd left in solution.     

Gene set enrichment analysis for non-monotone association and multiple experimental categories

Background  

Recently, microarray data analyses using functional pathway information, e.g., gene set enrichment analysis (GSEA) and significance analysis of function and expression (SAFE), have gained recognition as a way to identify biological pathways/processes associated with a phenotypic endpoint. In these analyses, a local statistic is used to assess the association between the expression level of a gene and the value of a phenotypic endpoint. Then these gene-specific local statistics are combined to evaluate association for pre-selected sets of genes. Commonly used local statistics include t-statistics for binary phenotypes and correlation coefficients that assume a linear or monotone relationship between a continuous phenotype and gene expression level. Methods applicable to continuous non-monotone relationships are needed. Furthermore, for multiple experimental categories, methods that combine multiple GSEA/SAFE analyses are needed.     

Stereotypic behavior and fecal cortisol level in captive giant pandas in relation to environmental enrichment

Stereotypic behavior is exhibited by a wide range of captive animals. Its association with hormones, especially elevated cortisol level and lack of naturalistic stimuli in the environment, has been little studied. This study hypothesizes that stereotypic behavior is caused by stress due to lack of appropriate, naturalistic stimuli in the environment. Using four adult pandas (Ailuropoda melanoleuca) in the Beijing Zoo from March–July in 2003, we tested the following predictions: 1) stereotypic behavior and fecal cortisol level will not change associated with the progress of reproductive state; 2) there is a positive correlation between the occurrence of stereotypic behavior and fecal cortisol level; and 3) environmental enrichment by adding a naturalistic stimulus will reduce both stereotypic behavior and fecal cortisol level. We did not find any significant differences in the occurrence of stereotypic behavior and fecal cortisol level but did find a significant difference in the total time engaged in displaying the stereotypic behavior among the three estrous periods. The level of stereotypic behavior was correlated with elevated fecal cortisol level. Enrichment simply by adding a naturalistic stimulus did not show significant effects on stereotypic behavior, or on fecal cortisol level. Our results supported the second prediction, but did not completely support the first and the third ones perhaps because of the small sample size. Additionally, our results showed that stereotypic behavior might be a response to a heightened level of cortisol. Zoo Biol 0:1–15, 2006. © 2006 Wiley‐Liss, Inc.     

Effects of chronic maternal stress on hypothalamo-pituitary-adrenal (HPA) function and behavior: no reversal by environmental enrichment

Maternal stress during pregnancy is linked to increased risk for impaired behavioral and emotional development and affective disorders in children. In animal models, acute periods of prenatal or postnatal stress have profound effects on HPA function and behavior in adult offspring. However, few animal studies have determined the impact of chronic exposure to stress throughout the perinatal period. The objective of this study was to determine the effects of chronic maternal stress (CMS) during the 2nd half of pregnancy and nursing on HPA function, locomotor behavior and prepulse inhibition in adult guinea pig offspring, as well as to determine whether environmental enrichment (EE) could reverse the effects of CMS. Guinea pigs were exposed to a random combination of variable stressors every other day over the 2nd half of gestation and from postnatal day (pnd) 1 until weaning (pnd25). Following weaning, offspring were housed in either standard conditions or EE. In both adult male and female offspring, there was no effect of CMS on basal or activated HPA function. CMS significantly increased locomotor activity in an open-field in male offspring, though no effect was observed in females. In female offspring, CMS disrupted PPI; however there was no effect on male PPI. EE had a number of effects on HPA function and behavior but in most cases these were independent of the influence of CMS. EE significantly elevated basal cortisol levels in male offspring at pnd70, whereas in female offspring, EE interacted with CMS to elevate basal cortisol levels from pnd35 to pnd70. In female offspring, EE decreased locomotor activity. In males, EE enhanced PPI; however in female offspring EE disrupted PPI. In conclusion, while CMS had minimal effects on HPA function, there were significant long-term sex-specific effects on behavior. EE did not reverse the effects observed as a result of CMS, but rather modified HPA function and behavior independently of CMS. Further, there was significant interaction of CMS with EE that resulted in elevation of basal HPA function in female offspring. These data, combined with previous studies from our laboratory, suggest that acute phases of maternal stress in late pregnancy may have greater long-term effects on HPA function and related behaviors than prolonged chronic maternal stress.     

Absolute enrichment: gene set enrichment analysis for homeostatic systems

The Gene Set Enrichment Analysis (GSEA) identifies sets of genes that are differentially regulated in one direction. Many homeostatic systems will include one limb that is upregulated in response to a downregulation of another limb and vice versa. Such patterns are poorly captured by the standard formulation of GSEA. We describe a technique to identify groups of genes (which sometimes can be pathways) that include both up- and down-regulated components. This approach lends insights into the feedback mechanisms that may operate, especially when integrated with protein interaction databases.     

Identification,enrichment, and isolation ofThiothrix spp. from environmental samples

We have developed a method to enrich, isolate, and identifyThiothrix spp. in environmental samples. This procedure employs low concentrations of organic compounds, the addition of reduced sulfur compounds (sulfide or thiosulfate), and preparation with spring water that containsThiothrix spp. The enrichment enhanced identification ofThiothrix spp. by promoting deposition of intracellular sulfur granules and inhibiting overgrowth by other bacteria. The relatively high calcium content of the spring water contributed to the culture procedure. With this technique,Thiothrix spp. were observed in two activated sludge systems, a municipal water storage tank, three springs, and four underground freshwater caves in the phreatic zone of the Floridan aquifer. Two differentThiothrix cultures have been isolated from a freshwater cave and a water storage tank by this procedure. It appears that media prepared with spring water known to supportThiothrix spp. can be designed to provide highly selective methods for isolation ofThiothrix spp. from a wide range of environments.Florida Agricultural Experimentation Station, Journal Series Number R-03446.     

Environmental enrichment: A GAP analysis

GAP analyses are tools used to inform us about the short-comings of a scientific area or necessities in social–economic problems. In the last 20 years, environmental enrichment as an area of scientific investigation has come of age; this can be clearly seen by the number of publications produced in this area. For example, a search on the database The Web of Science^©, using the keywords “environmental enrichment”, from 1985 to 2004 produced 744 articles. In this study we analysed these 744 articles and classified them by year into: type of environment (e.g., zoo, farm and laboratory); taxonomic classification (e.g., mammal, bird, etc.); type of enrichment (e.g., food, sensory, etc.); subject area (e.g., neurosciences and agriculture); country of publication; and gathered data on experimental design (e.g., sample sizes). Furthermore, we collected similar data on animal well-being and animal conservation for comparative purposes (keywords: “animal well-being” and “animal conservation”). The results from this study show that the number of environmental enrichment studies has been steadily increasing from a low level in the 1980s until 1999, when there was a noticeable acceleration in the number of articles published. Largely, this acceleration was a response to the growing interest in environmental enrichment by neuroscientists. The data also show a relative lack of, and recent decline in, publications in the area of agriculture. Thus, the data suggest a need for more research on enriching the lives of farm animals. Environmental enrichment publications over the 20 years of the study corresponded to 27% of all animal well-being publications in the period. One interesting comparison between enrichment and animal well-being revealed the virtual absence of research in animal well-being by neuroscientists. The detailed results of this study will help in identifying gaps in our knowledge about environmental enrichment, and how experimental designs might be improved.     

Philosophy of environmental enrichment: Past,present, and future

The brief tenure of environmental enrichment has been influenced both directly and indirectly by the field of psychology, from the work of B.F. Skinner to that of Hal Markowitz. Research on enrichment supports the supposition that an enriched environment does indeed contribute to a captive animal’s well‐being. Critical elements of effective environmental enrichment are 1) assessing the animal’s natural history, individual history, and exhibit constraints and 2) providing species‐appropriate opportunities, i.e., the animal should have some choices within its environment. This paper presents a historic perspective of environmental enrichment, proposes a broader, more holistic approach to the enrichment of animals in captive environments, and describes a framework or process that will ensure a consistent and self‐sustaining enrichment program. Zoo Biol 20:211–226, 2001. © 2001 Wiley‐Liss, Inc.