Cage ammonia levels during murine reproduction.

Monogamous pairs of inbred BALB/c and outbred CD-1 mice housed in M2 cages with a floor area of 330 cm2, produced a mean cage ammonia level of 26 ppm and 154 ppm respectively over a four day period prior to weaning their litters. A gradient of ammonia exists from the nest to the food hopper. By housing CD-1 monogamous pairs in RM2 cages which have double the floor area of M2 cages (676 cm2), a lower mean level of ammonia was recorded at the same stage of reproduction and air sampling. The CD-1 mice in particular, were subjected to high levels of ammonia when compared with long term human health and safety occupational exposure limits of 25 ppm.     

The effects of intracage ventilation on microenvironmental conditions in filter-top cages.

Filter-top cages, while effective in reducing cross contamination by particulate material including microbes, can also cause accumulation of the waste gases carbon dioxide and ammonia as well as increased intracage relative humidity. A prototype system which provided each cage with 23 air changes per hour through a nozzle inserted in the filter lid was evaluated. The ventilated cageing system was effective in reducing intracage carbon dioxide, ammonia and relative humidity levels. Mean weekly carbon dioxide levels were 2900 ppm lower, ammonia levels 240 ppm lower and intracage relative humidity levels 8% lower in the ventilated cages than in unventilated controls.     

A forced-air ventilation system for rodent cages

A novel forced-air ventilation system for rodent cages was developed. The apparatus was operated at an air flow rate of 56 L/min when used with a 230 mm wide X 450 mm long X 165 mm deep cage. Air velocity measurements in the cage did not exceed 8 m/min at animal (rat) height. The average NH3 concentration in a cage which housed two 250 g rats was less than 0.3 ppm at the end of the third day, whereas the concentration measured in a cage without the forced-air ventilation system was 150 ppm after 3 days. Tests of the water content of soiled bedding showed the forced-air ventilation system to provide a much drier environment for the rodents.     

The impact of reduced frequency of cage changes on the health of mice housed in ventilated cages

Our purpose in this investigation was to determine if we could reduce cage changing frequency without adversely affecting the health of mice. We housed mice at three different cage changing frequencies: 7, 14, and 21 days, each at three different cage ventilation rates: 30, 60 and 100 air changes per hour (ACH), for a total of nine experimental conditions. For each condition, we evaluated the health of 12 breeding pairs and 12 breeding trios of C57BL/6J mice for 7 months. Health was assessed by breeding performance, weanling weight and growth, plasma corticosterone levels, immune function, and histological examination of selected organs. Over a period of 4 months, we monitored the cage microenvironment for ammonia and carbon dioxide concentrations, relative humidity, and temperature one day prior to changing the cage. The relative humidity, carbon dioxide concentrations, and temperature of the cages at all conditions were within acceptable levels. Ammonia concentrations remained below 25 ppm (parts per million) in most cages, but, even at higher concentrations, did not adversely affect the health of mice. Frequency of cage changing had only one significant effect; pup mortality with pair matings was greater at the cage changing frequency of 7 days compared with 14 or 21 days. In addition, pup mortality with pair matings was higher at 30 ACH compared with other ventilation rates. In conclusion, under the conditions of this study, cage changes once every 14 days and ventilation rates of 60 ACH provide optimum conditions for animal health and practical husbandry.     

Preferences of farmed blue foxes for different floor types

In the first experiment, farmed blue foxes were allowed to choose for 1 week between four standard farm cages equipped with different floor materials: plastic-coated wire mesh, dry wood, dry sand and wet (summer) or icy (winter) sand. Resting consisted of 10-15 separate bouts/day occupying 50-60% of the total 24-h. There were no other differences in the use of the cages except that the time spent on, and the duration and number of resting bouts were lower on wet or icy sand, resting periods being more affected than activity. In the second experiment, two cages were connected with a 1.2 m tunnel. One cage was always elevated (50 cm) compared to that one which was lower. One cage of each pair had a wire floor whereas the other cage either had sand or wire floor. Sand floor was preferred for active behaviours and wire floor for resting if these were on elevated level. Of two identical wire-floored cages, the elevated one had the priority. Foxes preferred to rest on the same floor where they had finished their previous resting bout, often exclusively and independently of floor material or floor level.     

The effects of different rack systems on the breeding performance of DBA/2 mice

Housing systems for laboratory animals have been developed over a long time. Micro-environmental systems such as positive, individually ventilated caging systems and forced-air-ventilated systems are increasingly used by many researchers to reduce cross contamination between cages. There have been many investigations of the impact of these systems on the health of animals, the light intensity, the relative humidity and temperature of cages, the concentration of ammonia and CO(2), and other factors in the cages. The aim of the present study was to compare the effects of different rack systems and to understand the influence of environmental enrichment on the breeding performance of mice. Sixty DBA/2 breeding pairs were used for this experiment. Animals were kept in three rack systems: a ventilated cabinet, a normal open rack and an individually ventilated cage rack (IVC rack) with enriched or non-enriched type II elongated Makrolon cages. Reproduction performance was recorded from 10 to 40 weeks of age. In all three rack systems there was a similar breeding index (pups/dam/week) in non-enriched groups during the long-term breeding period, but the coefficients of variation in the IVC rack were higher for most parameters. This type of enrichment seems to lead to a decrease in the number of pups born, especially in the IVC group. However, there was no significant difference in breeding index (young weaned/female/week).     

Efficacy of wax matrix bait stations for Mediterranean fruit flies (Diptera: Tephritidae)

Tests were conducted that evaluated efficacy of wax matrix bait stations for Ceratitis capitata (Wiedemann) adults in Guatemala. Bait stations were exposed to outdoor conditions to determine effect of weathering on longevity as indicated by bait station age. Results of laboratory tests found that bait stations with spinosad and ammonium acetate remained effective for at least 31 d compared with pesticide-free controls, although there was some loss of efficacy over time. Percentage mortality for bait station strips with 2% spinosad and 1% ammonium acetate decreased from 100 +/- 0.0% on day 0 to 70 +/- 7.1% after 31 d. Ammonia concentration had little effect on percentage mortality although there was some indication that ammonia concentration affected number of flies observed on the bait stations. Bait station strips (one per cage) were more effective than controls for 6-8 wk when tests were conducted in field cages (3 m diameter x 2 m), but only 2-3 wk when tests were conducted in large (2.5 m high and 6.0 m wide and 7.5 m long) field cages. Longevity was restored when multiple bait stations (3, 6, or 12) were deployed per cage. Bait stations containing methomyl were used for field tests of efficacy for wild flies. Dipped lure bait stations, which were made by coating two edges of commercial ammonium acetate and trimethylamine lures, killed six times more flies than corn cob bait stations dipped into a Nulure/malathion solution. They also killed more flies than pesticide-free controls for 8 wk.     

Effect of acclimation to caging on nephrotoxic response of rats to uranium

Animal studies of the toxicity and metabolism of radionuclides and chemicals often require housing of rats in metabolism cages for excreta collection. Response of rats to toxic substances may be affected by environmental factors such as the type of cage used. Dose-response studies were conducted to assess the effects of two types of cages on the nephrotoxic response of rats to uranium from implanted refined uranium ore (yellowcake). The LD50/21 days was 6 mg of uranium ore per kilogram body weight (6 mg U/kg). The 95% confidence limit (C.L.) was 3-8 mg U/kg for rats housed in metabolism cages beginning on the day of implantation (naive rats). However, for rats housed in metabolism cages for 21 days before implantation (acclimated rats) the LD50/21 days was 360 mg U/kg (95% C.L. = 220-650 mg U/kg), which was the same value obtained for rats housed continuously in polycarbonate cages. This significant difference (P less than 0.01) in response of naive rats compared to response of acclimated rats appeared related to a significantly lower water consumption by the naive rats.     

Effects of housing density on nasal pathology of breeding mice housed in individually ventilated cages

The 2011 edition of the Guide for the Care and Use of Laboratory Animals includes new recommendations for the amount of floor space that should be provided to breeding mice. When pairs or trios of continuously breeding mice are housed in shoebox cages, they may have less than this recommended amount of floor space. High housing densities may adversely affect animal health, for example, by compromising air quality inside the cage. Hence, some institutions are carefully reevaluating the microenvironments of breeding cages. The use of individually ventilated cages (IVCs) to house research mice allows for greater control over the quality of the cage microenvironment. The authors evaluated the microenvironments of shoebox cages in an IVC rack system housing breeding and non-breeding Swiss Webster mice. Ammonia concentrations were significantly higher in cages housing breeding trios with two litters. Histopathologic lesions attributable to inhaled irritants such as ammonia were found in mice housed in breeding pairs and trios. The authors conclude that the microenvironments of cages in an IVC rack system housing breeding pairs and trios may be detrimental to animal health.     

Effects of housing density and cage floor space on three strains of young adult inbred mice

Some recommendations in the Guide for the Care and Use of Laboratory Animals (the Guide) are based on best professional judgment. Our current efforts are directed toward replacement with data-driven standards. We demonstrated earlier that young adult C57BL/6J mice could be housed with half the floor space recommended in the Guide without discernable negative effects. This report extends that work by examining optimal housing densities for young adult male and female BALB/cJ, NOD/LtJ, and FVB/NJ mice. These 8-week studies were initiated with 3-week-old BALB/cJ and NOD/LtJ mice and 3- to 5-week-old FVB/NJ mice housed in three cage types. We adjusted the number of mice per cage to house them with the floor space recommended in the Guide (approximately 12 in2 [ca. 77 cm2] per mouse) down to 5.6 in2 [ca. 36 cm2] per mouse. Early-onset aggression occurred among FVB/NJ male mice housed at all densities in cages having 51.7 in2 (ca. 333 cm2) or 112.9 in2 (ca. 728 cm2) of space. FVB/NJ male mice housed in shoebox (67.6 in2 [ca. 436 cm2]) cages did not exhibit aggression until the fifth week. Urinary testosterone output was density-dependent only for BALB/cJ male mice in shoebox cages (output decreased with increasing density) and FVB/NJ male mice. We conclude that all but FVB/NJ male mice can be housed with half the floor space specified in the Guide. The aggression noted for male FVB/NJ mice may have been due to their age span, although this did not impact negatively on the female FVB/NJ mice.     

Effect of cage population density on plasma corticosterone and peripheral lymphocyte populations of laboratory mice

The effect of different population densities of mice per cage on plasma corticosterone, peripheral lymphocytes and specific lymphocyte subpopulations was investigated. The animals were housed in groups of 2, 4 or 8 mice per cage and the blood samples were taken from each animal of these groups on days one, 7 and 14. A significant elevation (P less than 0.05) in plasma corticosterone concentration was observed in the group of 8 mice per cage on days one and 7 as compared with those of 2 or 4 mice per cage. The number of peripheral lymphocytes was significantly decreased in the groups of 2 (P less than 0.01) and 8 (P less than 0.05) mice per cage as compared with the group of 4 mice per cage on day one. A significantly decreased number of lymphocytes (P less than 0.01) in the group of 8 mice per cage continued to day 7. There were no significant differences in specific lymphocyte subpopulations observed among these groups. The results of this study suggest that a population density of 4 mice per cage induced minimal stress compared to that induced by the population densities of 2 or 8 mice per cage. Since stress is known to induce alteration in a variety of biological functions, the population density of mice per cage should be considered in the interpretation of research data.     

笼底类型对肉仔鸡行为的影响及其与胸囊肿发生率的关系

为研究笼养肉仔鸡胸囊肿发生的行为学机制,观察比较3种盒式笼(笼底分别由铁丝网、塑料片和竹竿组成)中肉仔鸡从3至6周龄的行为,以及胸囊肿发生率的差异。结果表明6周龄时,肉仔鸡在3种笼底上的伏卧行为虽无显著差异,但在行为格局中其比例最高(均在70%以上),而站立、行走和晃动3种行为之和仅占10%左右;竹竿笼底上的肉仔鸡行走频次、晃动频次和比例均显著高于铁丝和塑料笼底上的(均P<0.05),而竹竿笼底上的肉仔鸡胸囊肿发生率显著低于铁丝笼底上的(P<0.05);随着周龄增长,铁丝笼中肉仔鸡行走和晃动频次均减少,伏卧时间延长,胸骨承受的重量增大,这增加了胸部与铁丝网笼底接触及摩擦的几率和时间。实验结果说明,笼养肉仔鸡行为格局趋向静态单一化(动态行为频次降低,静态行为比例占优势)与其胸囊肿发病率的变化相一致,提示两者存在某种内在联系。这验证了我们提出的假设,即依赖于笼底类型和周龄的肉仔鸡行为趋向静态性是胸囊肿形成的必经环节。     

In vivo biocompatibility of aliphatic segmented polyurethane in rabbit

An aliphatic segmented polyurethane with soft to hard segment ratio 3 was synthesised using hexamethylene diisocyanate, polypropylene glycol 400 and 1,4-butane diol.A stainless steel cage implant system has been used to study thein vivo biocompatibility of this polyurethane. United States Pharmacopoeia negative control polyethylene was used for the comparison. Three cages, one with polyurethane another with United States Pharmacopoeia polyethylene and the third control empty cage were implanted subcutaneously in the dorsal aspect of rabbits. The inflammatory exudate surrounding the material was aspirated from the cages on 4, 7, 14 and 21 days after implantation. The total protein content in the exudate aspirated from all the 3 cages was significantly higher at 7 days than in the reported normal rabbit serum of New Zealand white rabbit but equal to that of our rabbit colony. The albumin concentration was lower in the initial period but increased at 21 days post implantation period in all the cages. Concentration of α₁, α₂ and γ-globulin also decreased in all cages at 21 days. Neutrophils were predominant in all the exudates aspirated from polyurethane, polyethylene and empty control cages during whole implantation period. This is attributed to the profound effect of the cages on the surrounding vasculature. Macrophage was found to be seen during acute phase of inflammation due to the migration of macrophage along with neutrophil towards the inflammatory lesion. The percentage of neutrophils showed a faster decline in the cage containing polyethylene at 21 days. The extra cellular alkaline phosphatase activity, though higher in exudate from cages containing polyurethane at 14 days post implantation, was same in all 3 cages at 21 days. Leucine amino peptidase activity was found to be decreased at 21 days of post implantation time though the empty control cage exhibited an increase at 14 days post implantation. The inflammatory response at 21 days was similar in polyurethane and the control polyethylene     

Performance and welfare of rabbit does in various caging systems

The objective of the study was to compare production and welfare of rabbit does and their kits housed in various types of cages. Female rabbits were randomly allocated to four groups with the following cage types: CN: common wire-mesh flat-deck cage, without footrest; CF: cage similar to the CN but with plastic footrest; ECWP: enlarged cage with wire-mesh platform; and ECPP: extra enlarged cage with plastic-mesh platform. All does were inseminated on the same day, 11 days after kindlings. Reproductive performance was evaluated during the first five consecutive kindlings. Severity of sore hocks was scored at each insemination. Location preference of the does and the platform usage of their kits were evaluated. Kindling rate, litter size (total born, born alive, alive at 21 and 35 days) and kit mortality were not significantly influenced by the cage types. The litter weight at 21 days was higher in ECWP and ECPP cages than in the CF group (3516, 3576 and 3291 g, respectively; P<0.001), and at 35 days the difference was only significant between the groups ECPP and CF (8712 and 8060 g, respectively, P<0.05). At 21 and 35 days of age, the kits were heavier in large (ECWP and ECPP) than in conventional cages (CF and CN) (P<0.001). At the fifth insemination, the percentage of rabbits with sore hocks’ score of 1 to 2 (0=intact foot pads; 1=no hairs, callus formed, <2.5 cm; 2=no hairs, callus formed, >2.5 cm) and 3 to 4 (3=callus opened, cracks present; 4=wounds) were 58%, 60%, 78% and 48%, and 0%, 5%, 0% and 48% in groups ECPP, ECWP, CF and CN, respectively. Higher number of daily nest visits was observed for CF does than for ECWP does (12.5 v. 5.9; P<0.05). The frequency of multiple nursing events (>2/day) was higher in the CF group than in the ECWP group (12.1 v. 3.2%; P<0.01). Within large cages, the does were observed on the platform more frequently in the ECPP cages compared with the ECWP cages (56.9% v. 31.7%; P<0.001). Similarly, 2.7% and 0.2% of kits at 21 days of age, and 33.2% and 5.2% of kits at 28 days of age, were found on the platforms of ECPP and ECWP cages, respectively. In conclusion, cages larger than the conventional ones improved kits’ weaning weight, plastic footrests and plastic-mesh platforms in conventional and/or large cages reduced sore hocks’ problems, plastic-mesh platforms were more used by both does and kits compared with the wire-mesh platforms.     

Position of operant cost affects blue foxes’ time budget between sand floor and mesh floor

The aim of the study was to assess whether positioning of the operant cost would affect blue foxes’ (Vulpes lagopus) behaviour and time budget between a mesh floor and sand floor. We built fourteen test apparatuses, six consisting of two fox cages with a mesh floor in both cages and eight with a mesh floor in one cage and a sand floor in the other cage. A cost could be imposed to pass through one-way doors between the cages. The effect of changing the cost to move from the mesh floor to the sand floor or from the sand floor to the mesh floor or between the two mesh floors was examined in 28 juvenile male blue foxes. The foxes’ time allocation between the cages was recorded for four different costs. The foxes’ behaviour was analysed in more detail at the lowest and highest costs. The visit duration increased considerably when leaving the cage became costly, but did not markedly change when entering was costly. The foxes spent less time on the sand floor than on the mesh floor. The foxes preferred to rest on the mesh floor, but rested also on the sand floor when there was a cost associated with leaving the sand floor. The sand floor stimulated digging, rooting and play. In conclusion, both positioning of the cost and the floor material affected blue foxes’ time budget between the two cages.     

Trade-off between floor level and floor material in farmed silver foxes

Farmed silver foxes (Vulpes vulpes) were allowed to balance their known preference for an elevated floor against their presumed preference for a sand floor. In Experiment 1, foxes had to choose between two identical cages, connected with an opening. One cage had a wire floor and the other had a sand floor, but the cages either were on the same (low or elevated) or on different levels (one cage 40 cm higher than the other). In Experiment 2, the cage pairs were connected with a 1.2 m long wire-mesh tunnel, one cage was always on a higher level (50 cm) than the other. In Experiment 1, foxes always preferred the sand floor during their active time. They also preferred the sand floor for resting, if it was on the same level as wire floor, but did not show any genuine preference if the floors were on different levels. In Experiment 2, foxes never preferred the lower floor. They preferred the elevated sand floor for activity and the elevated wire floor for lying. When two floors were identical they preferred the elevated one. Their rest consisted of 11-22 bouts, a major part of these being spent in the preferred cage. They also preferred a previous lying site to a new one, often exclusively and independently of floor material. In Experiment 1 foxes preferred the sand floor whereas in Experiment 2 they preferred the elevated floor indicating that the ability of a trade-off situation to rank resources depends on the method it is inflicted.     

Effects of semi-group housing and floor type on pododermatitis,spinal deformation and bone quality in rabbit does

The most common housing system for reproduction rabbits, individual cage housing on a wire floor, is increasingly scrutinized because of its potential detrimental impact on animal welfare. We compared three types of housing: (1) individual cage housing on a wire floor (3952 cm²/doe, maximum roof height 63 cm, one 1000 cm² plastic footrest/doe), (2) semi-group housing on a wire floor (5000 cm²/doe, roofless, one 1000 cm² plastic footrest/doe) and (3) the same semi-group housing, but with a fully plastic slatted floor. In all housing systems, does had free access to an elevated platform. In the semi-group housing pens, four does were housed communally during 21 days of the reproduction cycle (to allow more space for locomotion and to increase opportunities for social contact), and individually during the other 21 days of the cycle (to minimize doe–doe and doe–kit aggression that peaks around kindling). In all, 24 Hycole does were included per system. The does entered the experiment at 203 days of age (after their first parity). The experiment consisted of four reproductive cycles, ending at 369 days of age. Pododermatitis was scored in cycles 1, 2 and 4. At the end of the 4^th cycle the does were euthanized and X-rays were taken to assess spinal deformation. Tibia and femur length, width and cortical thickness were determined and bone strength was assessed using a shear test, as a measure of bone quality. Although severe pododermatitis was absent, the prevalence of plantar hyperkeratosis (hair loss and callus formation) at the end of the 4^th cycle was much greater on the wire floor (65% and 68% for semi-group housing and individual cages, respectively) than on the plastic floor (5%, P<0.0001), even though the wire floors were equipped with a plastic footrest known to decrease hyperkeratosis. In contrast to our expectations, semi-group housing did not affect the prevalence of spinal deformations (P>0.10), but in line with our expectations bone quality was affected favourably by semi-group housing. The tibial cortex (and to a lesser extent the femoral cortex) was thicker in semi-group housing than in individual cages (1.45, 1.46 and 1.38 mm for semi-group housing on wire, semi-group housing on plastic and individual housing on wire, respectively, P=0.045). What this increase in cortical thickness means in terms of doe welfare requires further study, as it may reflect an increase in activity resulting either from increased space for locomotion, or from fleeing aggressive pen mates.     

Effects of cage density on behavior in young adult mice

Optimal housing conditions for mice can be achieved by minimizing environmental variables, such as those that may contribute to anxiety-like behavior. This study evaluated the effects of cage size on juvenile mice through assessment of differences in weaning weight, locomotor skills, and anxiety-like behavior. Eighteen pairs of male and pregnant female Swiss-Webster (Cr:SW) mice were housed in 3 different caging scenarios, providing 429, 505, or 729 cm2 of space. Litters were standardized to 10 pups per litter in each cage. Mice reared in each caging scenario were assessed with the open-field, light-dark exploration, and elevated plus-maze tests. No differences in weaning weight were noted. Mice reared in the 505- and 729-cm2 cages explored a significantly larger area of the open-field arena than did those in the 429-cm2 cages. Those reared in the 505-cm2 cages spent more time in the center of the open field than did those in the 729-cm2 cages, suggesting that anxiety-like behavior may be increased in the animals housed in the larger cages. This study did not establish a consistent link between decreased floor space and increased anxiety-like behavior; neither does there appear to be a consistent effect of available floor area on the development of locomotor skills on mouse pups.     

Calibration and evaluation of field cage for oviposition study with Aedes (Stegomyia) aegypti female (L.) (Diptera: Culicidae)

Differences among results gathered from insect behavior studies conducted in laboratory and field situations are due to ambient variables that differ greatly between both environments. In laboratory studies the environmental conditions can be controlled whereas in field temperature, humidity and air velocity vary uncontrollably. The objective of this study was to calibrate and evaluate an experimental area (field cage) (14 x 7 x 3.5 m) subdivided into eight test cages (2.5 x 2.5 x 2 m) for use in behavioral oviposition tests of Aedes aegypti (L.) mosquitoes for developing a new methodology to assess attractants and oviposition traps. Test cage calibration involved: (1) minimal experiment duration tests; (2) optimal female release number per traps test and (3) trap placement tests. All tests used gravid A. aegypti females; 3-4 days post blood meal and the sticky trap MosquiTRAP to catch adults. Ninety percent of the females released were recaptured 2h after the beginning of the experiment, and this allowed up to 32 test repetitions/day to be conducted in the field cage. The minimum number of females necessary to conduct statistical analyses was 20 females/trap/test per cage. No significant difference was found in the behavioral response of gravid females to four different trap positions within test cages. Field trapping results with attractant were similar to those in the field cage. Therefore, the field cage could replace field trapping for evaluating at least mosquito traps and oviposition attractants for A. aegypti.     

A comparison of rodent caging systems based on microenvironmental parameters.

Four different mouse caging systems were evaluated for microenvironmental temperature, carbon dioxide, relative humidity (RH) and ammonia levels during a 7-day testing period. All caging systems evaluated had polycarbonate bases and consisted of either a molded polyester (MP) filter lid, one of two different polycarbonate filter lids, or no filter lid which served as a control. At 50% macroenvironmental RH (study I), all systems maintained an intracage temperature of 75.5 degrees F +/- 0.5 degrees. Both polycarbonate systems averaged greater than 2200 ppm of carbon dioxide more than the MP system and the controls. When compared with RH in the control cages, RH levels averaged over 20% and 5 to 8% RH greater in the polycarbonate filter lid systems and the MP system, respectively. There were no appreciable ammonia levels in either the MP or control systems. In the polycarbonate filter lid systems, ammonia levels were detectable on day 4 and were greater than 200 ppm by day 6. At 20% macroenvironmental RH (study II), there was a proportional 15 to 30% RH decrease from study I levels. Ammonia levels were undetectable in any system until day 7 and averaged only 17 ppm in one of the polycarbonate systems. Minimal differences were observed in studies III, IV and V when pine shavings were used instead of hardwood chips, a CD-1 stock instead of a DBA/2J strain, and different grades of filter inserts in the polycarbonate systems, respectively.