Bentonites are readily available clays used in the livestock industry as feed additives to reduce aflatoxin (AF) exposure; their potential interaction with nutrients is the main concern limiting their use, however. The objective of the present study was to determine the safety of a dietary sodium-bentonite (Na-bentonite) supplement as a potential AF adsorbent, using juvenile Sprague Dawley (SD) rats as a research model. Animals were fed either a control diet or a diet containing Na-bentonite at 0.25% and 2% (w/w) inclusion rate. Growth, serum, and blood biochemical parameters, including selected serum vitamins (A and E) and elements such as calcium (Ca), potassium (K), iron (Fe), and zinc (Zn) were measured. The mineral characteristics and the aflatoxin B1 sorption capacity of Na-bentonite were also determined. By the end of the study, males gained more weight than females in control and Na-bentonite groups (p ≤ 0.0001); the interaction between treatment and sex was not significant (p = 0.6780), however. Some significant differences between the control group and bentonite treatments were observed in serum biochemistry and vitamin and minerals measurements; however, parameters fell within reference clinical values reported for SD rats and no evidence of dose-dependency was found. Serum Na and Na/K ratios were increased, while K levels were decreased in males and females from Na-bentonite groups. Serum Zn levels were decreased only in males from Na-bentonite treatments. Overall, results showed that inclusion of Na-bentonite at 0.25% and 2% did not cause any observable toxicity in a 3-month rodent study.

With recent increased focus on positive welfare in animal welfare science, there is demand for objective positive welfare indicators. It is unclear whether changes in body surface temperature can be used to non-invasively identify and quantify positive states in mammals. We recorded continuous measurements of tail surface temperature using infra-red thermography (IRT) and concurrent behavioural observations in male and female Wistar rats (Rattus norvegicus). If tail surface temperature can differentiate between positive and negative experiences, we expect a qualitatively different response compared to negative experiences. Three groups of rats were presented with increasing magnitudes of food rewards (neutral/none, one and three rewards). The rats were placed in an arena to which they were habituated and filmed for 30 s before and 30 min after exposure to different rewards. Tail temperature initially decreased from the pre-reward baseline and subsequently returned towards baseline temperature. The overall pattern of the change was the same as for rats subjected to negative stimuli in previous studies. Nevertheless, dynamic changes in tail temperature, specifically the rate of recovery and the behavioural response (exploration), differed between neutral and rewarded rats but failed to distinguish reward magnitude. Sex differences were found in both thermal and behavioural responses, unrelated to reward magnitudes. Female rats exhibited a greater initial response with a slower recovery than male rats, emphasising the value of using of both sexes in animal welfare research. This study improves our understanding of the effects of positive emotions induced by food reward on peripheral body temperature and behaviour.

Rodent control tends to involve methods that cause animal suffering, but little attention has been paid to the animal welfare implications of rodent control. The aim of the current study was to gain insight into the opinions and attitudes of clients of Dutch pest controllers, regarding liminal rodents, rodent control, and rodent welfare. A better understanding of their attitudes may contribute to more ethical rodent management programmes. An online survey among 248 clients of Dutch pest controllers was carried out. Respondents, especially those within the agricultural sector, have a relatively negative attitude towards rats and mice. Respondents in the agricultural subgroup do not consider the welfare of liminal rodents important. They also think that the welfare impact of commonly used control methods is limited, and they have low tolerance levels for the presence of rodents. Respondents from other sectors have a far more positive attitude towards rats and mice, consider their welfare to be of greater importance, have a greater estimation of the welfare impact of control methods and show greater tolerance levels towards rodents. The respondents from the latter subgroup have a similar attitude compared to Dutch pest controllers participating in a previous survey. The findings of the current study firstly provide useful information for the further development and practical implementation of preventive control methods. Secondly, they provide input for a more animal-friendly rodent control and for the development of an assessment framework to support ethical decision-making. Finally, they can be helpful for further research and the communication and co-operation between professional pest controllers and their clients.

Severity assessment in animals is an ongoing field of research. In particular, the question of objectifiable and meaningful parameters of score-sheets, as well as their best combination, arise. This retrospective analysis investigates the suitability of a score-sheet for assessing severity and seeks to optimise it for predicting survival in 89 male Sprague Dawley rats (Rattus norvegicus), during an experiment evaluating the influence of liver cirrhosis by bile duct ligation (BDL) on vascular healing. The following five parameters were compared for their predictive power: (i) overall score; (ii) relative weight loss; (iii) general condition score; (iv) spontaneous behaviour score; and (v) the observer’s assessment whether pain might be present. Suitable cut-off values of these individual parameters and the combination of multiple parameters were investigated. A total of ten rats (11.2%; 10/89) died or had to be sacrificed at an early stage due to pre-defined humane endpoints. Neither the overall score nor any individual parameter yielded satisfactory results for predicting survival. Using retrospectively calculated cut-off values and combining the overall score with the observer’s assessment of whether the animal required analgesia (dipyrone) for pain relief resulted in an improved prediction of survival on the second post-operative day. This study demonstrates that combining score parameters was more suitable than using single ones and that experienced human judgement of animals can be useful in addition to objective parameters in the assessment of severity. By optimising the score-sheet and better understanding the burden of the model on rats, this study contributes to animal welfare.

There is some evidence that rats benefit from social housing and from some forms of environmental enrichment, such as platforms and shelters. It is less clear whether they benefit from more spacious cages. There is a lack of information about the relative benefits of social contact, enrichment and increased space, because existing studies tend to concentrate on only one of these variables at a time. The current experiment used economic demand procedures as a method to compare, on a single scale, qualitatively different environments with a standard home cage. The data indicate that rats show a high demand for social contact, and a low demand for a larger cage or one containing pillars or novel objects. This finding suggests that social housing of laboratory rats should be strongly advocated.

Rats are a well-understood and widely used laboratory species that should be provided with environmentally enriched caging in line with modern animal welfare guidelines. This paper reviews which sources of enrichment are effective and should be prioritised, and how methods for providing enrichment might be selected using rats’ preferences as a guide. Rats demonstrate high demand for social contact and prefer larger cages, and cages with shelters, nesting material and foraging devices. Rats also discriminate between different methods of providing a given type of enrichment. It is clear that rats should be provided with enrichments such as social contact and shelter, and, in fact, that these should probably be considered basic husbandry requirements rather than optional improvements. It is still difficult, however, for animal caretakers to access proven, standardised methods for providing appropriately enriched caging, and the level of enrichment routinely provided to most rats in the laboratory appears to be low. Further research is required to assess the impact of enrichment upon research variables and to develop commercially viable enrichment products for rats in the laboratory.

In rodents, cage cleaning increases cardiovascular and behavioural activity for several hours, which are commonly interpreted as stress responses. In mice, post-cleaning activity also includes aggression, which can cause serious injuries. This study was part of a long-term investigation into the effects of cage cleaning frequency on rat behaviour and welfare. Here we aimed to ascertain whether post-cleaning activity is stress- or aggression-related, thereby leading to recurrent acute reductions in welfare, or simply a result of non-aversive stimulation. Male Wistar (n = 160) and Sprague–Dawley (n = 160) rats, kept in four animal units, had their cages cleaned twice per week, once per week or once per fortnight, and were kept on one of two types of bedding. Behaviours were recorded in detail before and after cage cleaning for 20 weeks, as was the aversion-related Harderian gland secretion, chromodacryorrhoea (‘red tears‘). Cage cleaning caused decreased resting and increased feeding, walking, bedding manipulation and sheltering for at least 30 min after the disturbance. Skirmishing also increased markedly for 15 min after cleaning, but decreased thereafter to below baseline levels. Unlike in mice, all skirmishing was non-injurious and play-like. The frequency of cage cleaning did not affect the magnitude of this skirmishing peak, but rats that had their cages cleaned more frequently settled more quickly after cleaning. Surprisingly, chromodacryorrhoea decreased after cage cleaning; this could mean that rats find soiled cages stressful or alternatively, like many disturbances, cage cleaning might provoke frequent, curtailed bouts of grooming, thereby removing the secretion. Rats also manipulated aspen bedding more than paper bedding. Overall, we found no evidence that cage cleaning caused rats any acute decrease in welfare — a finding consistent with additional data we have obtained on the lack of preference by rats for soiled over clean cages, and a lack of long-term, behavioural and physiological responses to being cleaned frequently or infrequently.

The effect of providing a shelter to single-housed rats was measured in terms of the preference shown for a cage containing a shelter compared with a barren cage, the range of behaviours performed and the apparent fearfulness of the animals. All animals showed a strong preference for cages containing a shelter and rats housed in this environment showed increased exploratory behaviour and were apparently less fearful, based on their willingness to leave the home-cage. It would seem appropriate to provide enclosed shelters within the cages of laboratory rats as a way of improving their environment.

Various tools have been developed over previous years to study the welfare of laboratory animals. These include preference tests, which are commonly used to evaluate housing environments. Preference tests, however, have some pitfalls: they supply information only on the animals’ present preferences, and they allow the animal the choice only between the options offered. Other methods based upon the collection of clinico-chemical data require handling of the animals, which can be stressful in itself. An alternative may be to use telemetry to measure the changes in physiological parameters caused by different environmental conditions. The aim of this study was to use telemetry to evaluate the short-term impact of housing conditions on rodents. We monitored heart rate, blood pressure and body temperature in rats kept on three different types of flooring — bedding, grid floors and plastic floors. The study revealed significant differences in systolic and diastolic blood pressure, heart rate and body temperature between rats housed in the three conditions, indicating that both grid floors and plastic floors are more stressful for the animals than bedding. The observed differences did not diminish over the two-week observation period. The grid-floor housing induced elevations in blood pressure and heart rate. Blood pressure remained elevated even when the animals were returned to standard bedding, whereas the heart rate declined back to its original value immediately in response to this shift. This study shows that telemetry is a very effective tool but that it needs integrating with other methods: in addition, a greater understanding of the biological significance of the changes in cardiovascular parameters is required before the hypothesis that these changes represent an indication of distress can be accepted.

Isolating an animal refers to the situation where the animal is physically fully demarcated from conspecifics without physical, visual, olfactory and auditory contact. Animals housed in separate cages in the same room are, although deprived of physical and visual contact, still in olfactory and auditory contact, and thus not totally isolated. During the fifties and sixties several studies claimed to show physiological and behavioural differences between individually and group housed rats and mice. The so-called ‘Isolation Syndrome’ characterised by changes in corticosterone levels, metabolism, growth, and behaviour was introduced, rather as a model for psychoneurosis than through any concern for animal welfare. Today, it is often stated as common knowledge in laboratory animal science textbooks that individual housing as well as isolation of rats and mice has an effect on physiology and behaviour. It is, however, unclear whether this effect actually impairs animal welfare.

The aim of this paper is to analyse studies on individual housing of mice and rats to evaluate whether there is documented proof that individual housing affects welfare, and, alternatively whether it is possible to house these animals individually without negative impact on welfare, eg by providing special housing improvements.

A range of studies have shown that individual housing or isolation has effects on corticosterone, the open field behaviour, barbiturate sleeping time and the metabolism of different pharmaceuticals in the animals. However, this review of 37 studies in rats and 17 studies in mice showed divergence in test results difficult to explain, as many studies lacked basal information about the study, eg information on genetic strains and housing conditions, such as bedding, enrichment and cage sizes. Furthermore, test and control groups most frequently differed in cage sizes and stocking densities, and behavioural tests differed in ways which may very well explain the differences in results. Overall, there seemed to be an effect of individual housing, although it may be small, and it seems reasonable to assume that, through making small changes in the procedures and housing environments, the effects can be minimised or even eliminated. More well-controlled and standardised studies are needed to give more specific answers to the questions this issue poses.

Animals can communicate with one another through various types of signals. Evidence is presented that in certain experiments with rats, stress as induced by experimental treatment may give rise to the production of signals that affect non-treated animals housed nearby. Such communication between test and control animals may cause biased results and disturbed welfare of the latter. Communication of stress may be prevented by separate housing of control and test animals, but this could introduce another source of bias.

Three inbred strains of male laboratory rat (BN/HsdCpb, BDIX/Or1Ico and LEW/Mol) were provided with nest boxes and nest materials, and were observed for nest-building activity. After 7 days, each cage and nest box was examined. Each nest was weighed and scored for complexity, and returned to the cage. This was repeated after a further 7 days and the nest removed completely. This routine was repeated three times. All three strains of rat built nests inside the nest box and showed the same stages of construction. There was a significant increase in nest complexity between day 7 and day 14 in the strains BN and BDIX. Furthermore, BDIX rats used significantly more material for the nests, compared with the BN and LEW rats. In a second experiment, using the same rats, nest material was offered in four different ways. LEW rats used nesting material irrespective of where it was placed; BN rats only used straw placed on the top of the cage when no alternative was provided in the cage, and would not use the nest box roof when it was covered with bedding; whereas BDIX rats would only use nest material placed within the cage and would not use straw placed on the cage lid. BN rats also used nest material to cover the entrance to the nest box, a practice not carried out by the other strains. This study demonstrates that these rat strains have retained their natural nest-building behaviour. We suggest that the correct stimuli must be provided in order for this behaviour to be exhibited; in addition, the way in which the nest materials are provided must be in accordance with strain-specific characteristics.

The provision of foraging opportunities may be a simple way of improving an animal's welfare, but this approach has been neglected for laboratory rats (Rattus norvegicus). Standard housing contains little enrichment, and food is often provided ad libitum, which may result in inactivity and obesity, especially in mature males. Foraging enrichments may offer a way to correct these deficiencies. This study compared three potential enrichments — a limited-access hopper, gnawing sticks and a foraging device — to standard housing and feeding conditions, in order to examine their effects on rat body weight, food consumption, behaviour and preferences. The subjects were 12 mature male Wistar rats. Effects were assessed from daily weighing and from video records of the rats' behaviour over 24 h periods. The rats' preferences were determined using a four-way test system in which they could choose between a standard cage and cages offering the three potential enrichments. Compared to the standard housing and feeding, the limited-access hopper had a tendency to reduce food consumption, but the time spent feeding increased. The gnawing sticks provided the rats with the opportunity to gnaw, but did not affect other behaviours or body weight. The foraging device had the benefits of reducing aggression and allowing the rats to search for and manipulate food, but resulted in significant gains in body weight. Additionally, the foraging device was the preferred feeding source. Of the four possible feeding locations, the rats spent the least amount of time in the standard cage. The foraging device provided the most benefits but requires further modification to address problems of obesity.

The relationship between non-communicable diseases and eating behaviour has long been attributed to a surplus of food and energy. However, the increase in the prevalence of non-communicable disease and their underlying low-grade inflammatory milieu among people of low socio-economic status has highlighted the existence of a confounding factor. In this work, we aim to study the effect of lysine deficiency on some inflammatory markers in the absence or presence of an inflammatory insult (lipopolysaccharide (LPS)). For this purpose, thirty-two 5-week-old male Sprague Dawley rats were randomly distributed into four groups: (1) control diet, (2) control diet+LPS, (3) lysine-deficient diet and (4) lysine-deficient diet + LPS. Groups were only allowed their experimental diets for 4 weeks, during which LPS (50 µg/kg) or saline injections were administered intraperitoneally three times per week. The study showed that lysine deficiency blunted growth and body compartments development, decreased albumin production and elevated liver C-reactive protein (CRP) expression, independently of IL-6 and IL-1β, the main precursors of CRP. Also, the insufficient levels of lysine in the diet increased hyperactivity and triggered an anxiety-like behaviour, exacerbated with LPS. This work presents evidence that various physiological changes are associated with the absence of a sufficient amount of lysine in the diet and can potentially increase the risk factor for diseases. Thus, the increment in non-communicable disease among the low socio-economic status populations, who heavily rely on cereals as a main source of protein, can be, at least partially, blamed on low lysine availability in diets.

Neonate rats have played an important and unique role within the memory literature. Specifically, they are relatively naïve to experience, can be trained in an ethologically-valid way, using a single trial, which is not aversive and can demonstrate retention for at least 24 h, post-training. As such, they have provided salient insights into the biological mechanisms underlying the memory trace and brain development. The task of choice for rat pups is one using odour preference requiring the removal of each pup from the nest/dam for a ten-minute training trial. For such young animals this may reasonably lead to undue stress and the potential of subsequent rejection by the dam. Little research has considered whether the training duration could be substantially shortened to provide significant animal welfare benefits while maintaining, if not improving, task efficacy. This issue was addressed in the current paper using six-day old Wistar rats (n = 175) exposed to a single-trial, odour-preference task using either a standard ten-minute training trial or a shorter two-minute training trial. Exposing rat pups to the training odour for two minutes did not compromise the level of discrimination observed at test 24 h later. This finding suggests that significantly shorter training trials can be used without compromising retention levels at test. This not only has obvious welfare benefits, but may reasonably be considered to reduce pups’ stress levels which are known to alter both the strength and timing of the memory trace.

Single housing is believed to be chronically stressful and to have a negative impact on welfare and cognition in rats (Rattus norvegicus). However, single housing does not consistently evoke stress-like responses nor does it consistently impair cognitive performance. In an experiment in which all cages were separated by an opaque barrier, single- and pair-housed pigmented (dark-eyed) rats performed equally in a cognitive test and displayed similar levels of anxiety during testing. Additionally, bar biting in the home cage did not differ between the two groups. Stress levels both during cognitive testing and in the home cage were higher than those we have previously reported when rats were housed without opaque barriers between the cages. We conclude that visual interactions between rats in different cages may be of sufficient significance that single housing in a cage with a view to neighbouring rats and to the rest of the laboratory holding room may be preferable to pair housing in a cage without this view.

Since the release of the revised Appendix A from the Council of Europe for housing of laboratory animals there have been claims that laboratory animals should be housed under more complex conditions; known popularly as enrichment. A number of studies have expressed concerns that this may increase uncontrollable variation in the animals, thereby creating the need for greater numbers of animals. Within neurobiology there would appear to be a scientific basis for such concern. However, even though this may be used as an argument for denying the animal environmental enrichment, it is unclear whether there is any basis for concern within other research areas. The aim of this study, therefore, was to explore whether clinical pathology and cardiovascular parameters were influenced by housing rats under environmentally enriched conditions. Male, Sprague-Dawley rats were housed under three different regimes: non-enriched, standard-enriched (according to the guidelines of the Council of Europe) and extra-enriched with a shelf and higher cages. All housing forms were based upon commercially available, standardised equipment. A total of 41 different parameters were monitored via clinical pathology, telemetry and coagulation tests and virtually no differences were observed in relation to the manner in which the rats were housed. The uncontrollable variation observed in our study was compared to within-strain variation data supplied from the breeder and was relatively low in all three types of housing. We conclude, based upon our studies in male, Sprague-Dawley rats, that so far there is no basis for concern that enriched housing will lead to increased group sizes when using animals for research within this field and, as such, there is no reason not to enrich the environment of such rats.

Thyroid C-cells secrete the hormone calcitonin (CT) which acts as an inhibitor of bone resorption. Our aim was to examine the age-related changes in the structure and function of CT-producing C-cells, using histomorphometric, ultrastructural, and biochemical analyses. We used young adult (3-months-old), middle-aged (16-months-old), and old (24-months-old) male rats. The peroxidase-antiperoxidase method was applied for localization of CT. Stereological analysis was performed using the newCAST stereological software package. Serum samples were analyzed for the determination of CT, testosterone (T), calcium (Ca2+), and phosphorus (P). We found a significant increase in the volume density (Vv) of C-cells in both older groups (p < 0.05). The percentage of smaller volume range C-cells increased (p < 0.0001), while the proportion of greater volume range C-cells decreased (p < 0.05) with ageing. Ultrastructural analysis revealed a larger number of secretory granules in older rats. Serum CT increased (p < 0.001), while serum T and P were reduced (p < 0.01) in older rats. Serum Ca2+ was lower (p < 0.0001) in middle-aged rats compared to young adults. We revealed a 20% incidence of C-cell hyperplasia in older rats and one case of medullary thyroid carcinoma in an old rat. Our findings indicate that the ageing process causes significant histomorphometric changes at the thyroid C-cell level.