Rodent Bedding technical info and Beddinig biblio[3] - University of ...

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Rodent Bedding biblio review Domer, DA, Erickson, RL etal. 2011. The Impact of Bedding Type on Cage Change out Frequency. -­‐The frequency of cage changes varies among institutions as a result of several considerations: animal stress, allergen exposure to personnel, experimental interference, and costs associated with bedding and sterilization procedures. The goal of this study was to evaluate the effectiveness of a new sanitized corncob bedding material as compared with standard corncob in a ventilated mouse rack system. Intracage ammonia levels, bacterial growth and absorptive capacity of bedding were measured for cages of female C57BL/6 mice under standard and autoclaved conditions on static and ventilated racks in a barrier facility. Intracage ammonia concentration was measured daily, and cages were removed when measurements were equal to or greater than 25 ppm. Quantity of bacterial growth and bacterial species in bedding were determined at the time of cage removal. Bedding absorptive capacity and bacterial load were also evaluated in all conditions without the addition of mice. Cages with nonautoclaved sanitized corncob bedding took significantly longer to reach ammonia concentrations of 25 ppm than standard corncob. Autoclaved sanitized corncob bedding did not differ significantly from nonautoclaved standard corncob in length of time required to measure 25 ppm ammonia. All nonautoclaved sanitized corncob cages remained in the study a minimum of 3 wk. No significant differences were noted on bacterial load at the conclusion of mouse housing. Standard corncob was significantly more absorbent than sanitized corncob bedding, and autoclaved sanitized corncob bedding was significantly more absorbent than autoclaved corncob. This study demonstrated that mouse cages with nonautoclaved sanitized corncob bedding on ventilated racks may be used with a cage change interval of 3 wk. Horn MJ, Williams SV, et al. 2010. The Impacts of Cage Density, Sanitation Frequency, and Bedding Type on Selected Measures of Animal Wellbeing, Health, and Cage Environment. AALAS Scientific Session. -­‐The objective of this study was to evaluate the effects of cage density, sanitation frequency, and bedding type on animal growth, cage conditions, and animal welfare. Sprague–Dawley rats and C57BL/6 mice of both sexes at 3 wk of age were randomly selected from production colonies and allotted into one of 12 treatments. Animals were allotted based on gender, bedding type, and cage density and sanitation frequency for an 8-­‐wk period. Bedding material optimization trials involved comparison of shredded aspen, cellulose, or a 50:50 mixture of shredded aspen to cellulose, with internal cage density standards and sanitation procedures measured against those recommended by the Guide. Body weight, feed disappearance, cage ammonia and ATP concentrations, behavior, and morbidity and mortality were assessed weekly while fecal corticosterone and nasopharyngeal and cecal microbiology as well as lung histopathology (rats only) were monitored at the culmination of the trial. In Sprague–Dawley rats, none of these parameters were significantly affected by cage density, sanitation frequency, or bedding type. Spurious effects on feed disappearance, cage ammonia, and cage ATP were reported that did not appear to represent an important data trend. In C57BL/6 mice, parameters indicative of animal health and welfare were, in general, not significantly affected by cage density, sanitation frequency, or bedding type. However, periodic spikes of cage ammonia concentrations and ATP levels were recorded in cages housed according to internal cage density and sanitation frequency standards compared with Guide standards, and in cages bedded with aspen compared with cellulose or aspen-­‐cellulose mixed bedding. Ongoing studies and historical data support the finding that slight deviance from the cage density and sanitation frequency standards set forth in the Guide does not negatively affect animal health, welfare, or

production parameters at our institution. These parameters appear to be credible measures of animal health and wellbeing and may be useful for evaluating performance standards for animal husbandry. Krohn, TC, and Hansen, AK. 2008. Evaluation of corncob as Bedding for Rodents. Scand. J. Lab. Animal Sci. 35:231-­‐236. -­‐Previous studies have shown that the ammonia level in cages using corncob bedding is reduced compared to cages with aspen bedding. The reduced level of ammonia prolongs the interval between cage changing, and it may therefore be beneficial for the facility to use corncob. When analyzing the bedding’ ability to absorb water, corncob showed lower water absorption compared to aspen bedding; the more corncob in the mixture, the less water is absorbed. Both mice and rats rejected cages with pure corncob during the day, and none of the animals preferred corncob mixed with aspen, only equally accepted it. In conclusion, neither rats nor mice prefer corncob, even not is mixtures with aspen bedding and enrichment. In the light of the common standard for bedding being wood chips, and the lack of preference for corncob mixture corncob seems to be a poor alternative to wood based bedding. Leya, L, Mikusa, S etal. 2011 Effect of Corncob bedding with Aspen Chip Bedding on Rat EEG and Pain Models. AALAS Poster. -­‐Nonexperimental variables can impact animal studies. We switched from aspen chip to corncob for its absorbency. Subsequently, rats in EEG studies were sleeping less during light cycle recordings. Sleep reduction can negatively impact the validity of EEG drug studies. We conducted a study to determine whether the corncob bedding was the cause of reduced sleep. Male SD rats were implanted with electrodes over the frontal and parietal cortices with a reference electrode implanted over the cerebellum. The rats were maintained on a normal 12:12-­‐h light:dark cycle (lights on at 0600). Quantitative analysis of the EEG was performed using fast Fourier transform (FFT). Prior to the study, rats (n = 15) were on corncob bedding in both home cages and recording chambers for 5 wk, thus, were habituated to the bedding. Only the EEG chamber bedding was changed during the study. All rats were recorded on both bedding types on different days over the course of the experiment. Results showed that corncob bedding resulted in a significant decrease in the amount of time spent in slow-­‐wave sleep during hours 0900 and 1000 as compared with aspen chip (P < 0.001 and P < 0.01, respectively; Bonferroni post hoc test). A 2-­‐way ANOVA showed no effect of time (P = 0.2173), with a significant effect of treatment (P < 0.0001) and interaction (P = 0.0275). In addition, altered mechanical sensitivities were seen in rat models of inflammatory and neuropathic pain when rats were housed on corncob bedding compared with aspen chip. Additional overt pain behaviors were observed in corncob housed rats including protection (lifting) of the injured paw, pushing the bedding aside and a preference for areas free of bedding. These findings support other published literature suggesting that rats prefer wood chip to corncob bedding. The IACUC requested that all corncob bedding be removed from rodent cages based on this data. Locklear, J, Thigpen, J. etal. 2010. Corncob Bedding Spiked with Zearalenone Significantly Advances the Timing of Vaginal Opening in Immature CD-­‐1 Haired and SKH-­‐1 Hairless Mice. AALAS Poster

-­‐We previously reported that the estrogenic mycotoxin, Zearalenone (ZEA), naturally found in commercially available corncob bedding significantly advances time of vaginal opening (VO) in CD-­‐1 mice. ZEA is ubiquitous in corncob beddings and may impact estrogenic studies involving weak estrogenic endocrine disruptor compounds (EDCs). We conclude that the hairless mouse is more sensitive to ZEA than the CD-­‐1 mouse and the primary route of exposure is via the skin, since mice were not observed ingesting the bedding. This study confirms our earlier report showing the ZEA in corncob bedding may significantly impact the results of studies evaluating the estrogenic activity of EDCs. Markaverich, B, Mani, S et al. 2002. A Novel Endocrine-­‐Disrupting Agent in Corn with Mitogenic Activity in Human Breast and Prostatic Cancer Cells. Envir. Health Pers. 110:169-­‐177. -­‐Housing adult rats on ground corncob bedding impedes male and female mating behavior and causes acyclicity in females. The suppressive effects on ovarian cyclicity are mimicked by a mitogenic agent purified from the ground corncob bedding, which stimulates the proliferation of estrogen receptor (ER)-­‐positive and ER-­‐negative breast cancer cells. CM also stimulates the proliferation of PC-­‐3 human prostatic cancer cells in vitro, and the growth rate of PC03 cell xenografts is accelerated in nude male mice housed on ground corncob as opposed to pure cellulose bedding. Consequently, this endocrine-­‐disrupting agent in ground corncob bedding may influence behavioral and physiologic reproductive response profiles and maligent cell proliferation in experimental animals. Barry M. Markaverich, Jan R. Crowley, Mary A. Alejandro, et al. Leukotoxin Diols from Ground Corncob Bedding Disrupt Estrous Cyclicity in Rats and Stimulate MCF-­‐7 Breast Cancer Cell Proliferation. Environ Health Perspect. 2005 December; 113(12): 1698–1704. Published online 2005 August 8. PMCID: PMC1314908 -­‐Previous studies in our laboratory demonstrated that high-­‐performance liquid chromatography (HPLC) analysis of ground corncob bedding extracts characterized two components (peak I and peak II) that disrupted endocrine function in male and female rats and stimulated breast and prostate cancer cell proliferation in vitro and in vivo. The active substances in peak I were identified as an isomeric mixture of 9,12-­‐oxy-­‐10,13-­‐dihydroxyoctadecanoic acid and 10,13-­‐oxy-­‐9,12-­‐dihydroxyoctadecanoic acid, collectively designated tetrahydrofurandiols (THF-­‐diols). Studies presented here describe the purification and identification of the HPLC peak II component as 9,10-­‐dihydroxy-­‐12-­‐octadecenoic acid (leukotoxin diol; LTX-­‐diol), a well-­‐known leukotoxin. A synthetic mixture of LTX-­‐diol and 12,13-­‐dihydroxy-­‐9-­‐octadecenoic acid (isoleukotoxin diol; i-­‐LTX-­‐diol) isomers was separated by HPLC, and each isomer stimulated (p < 0.001) MCF-­‐7 cell proliferation in an equivalent fashion. The LTX-­‐diol isomers failed to compete for [3H]estradiol binding to the estrogen receptor or nuclear type II sites, even though oral administration of very low doses of these compounds (>> 0.8 mg/kg body weight/day) disrupted estrous cyclicity in female rats. The LTX-­‐diols did not disrupt male sexual behavior, suggesting that sex differences exist in response to these endocrine-­‐disruptive agents.

-­‐Keywords: breast cancer, corncob bedding, endocrine disruptor, estrous cycles, leukotoxin diols Ras, T, van de Ven, EG, etal. 2002. Rats’ preferences for corn versus wood based bedding and nesting materials. Lab Animal. 36: 420-­‐425. -­‐Corn by-­‐products can be used as bedding and nesting products. Corncob bedding resists ammonia buildup and corn husk nesting material resists dampness. It is not clear whether these advantages are at the expense of animal comfort. Corncob was compared to aspen chip bedding, and corn husk to paper strip nesting material. Data from 20 rats with differential early bedding experience suggested that they prefer aspen chip, but are also biased towards the bedding they were raised on. Thus, corncob products are not recommended except in situations where air quality and/or flooding are significant problems. Smith, E, Stockwell, JD etal. 2004. Evaluation of cage Micro-­‐Environemtn of Mice Housed on Various Types of Bedding Materials. Contemp. Topics AALAS. 43:12-­‐17. -­‐In general, we observed little effect of bedding types on in cage temperature or humidity; however, there was considerable variation in ammonia concentrations. The lowest ammonia concentrations occurred in cages housing mice on hardwood bedding or a mixture of corncob and alpha cellulose. Thigpen, J, Kissling, G etal. 2010. The Impact of Rodent Diets and Bedding in Studies Evaluating the Estrogenic Activity of Endocrine Disruptor Compounds. AALAS Poster. -­‐Bisphenol A (BPA) is a ubiquitous estrogenic compound of great current concern because it is found in many places, such as plastic rodent cages, bottles, can liners, and dental sealants, and can affect humans and wildlife. The lowest adverse dose effect levels in animals are questionable and in some cases nonreproducible. Factors affecting the results of BPA studies include animal species/strain, age, sex, dose, route, time and duration of exposure, diet, and bedding. This report reemphasizes the impact that diet and bedding, containing high concentrations of estrogenic compounds, can have on studies evaluating the adverse effects of low doses of BPA, a weak estrogenic endocrine disruptor compound (EDC). We reviewed 100 reports on BPA published between 1997 and 2010 and asked the following questions to determine whether diets and beddings were identified; whether the estrogenic content were determined and reported; and the BPA doses used. A total of 45 mice and 55 rats studies were included, with the diet and bedding used being reported in 50% and 15% of the reports, respectively. The diet was reported, but not properly identified in 18% of the reports. Phytoestrogen-­‐reduced diets were used in 5% of the studies. Estrogenic assays were performed on 10% of diets. Most reported diets were high in phytoestrogens and most reported rodent bedding was corncob bedding. We concluded that an estrogenic-­‐free diet and bedding should be used for low dose BPA studies (< 50μg/kg BW/d); in some studies, the animals were exposed to more dietary daidzein and genistein per day than the daily administered dose of BPA. Based on our calculations, mice that were exposed to diets high in phytoestrogens are receiving several times more dietary estrogens daily than from the dose of BPA. Journals should require estrogenic content of the diet and bedding be reported for all studies.

Whiteside, TE, Thigpen, JE et al. 2010. Endotoxin, Coliform and Dust Level in Various Types of Rodent Bedding. JAALAS 49:184-­‐189. -­‐Paper bedding types contained significantly less endotoxin than did other bedding types; the highest levels of endotoxin were detected in hardwood and corncob beddings. Coliform counts varied from less than 10 to 7591 cfu/g in corncob, less than 10 to 137 cfu/g in hardwood beddings, and less than 10 cfu/g in paper beddings. Average dust content was less than 0.15% in all commercial bedding types. Zahorsky-­‐Reeves, J , and Castellani, LW. 2010. Housing Mice on Corncob bedding versus Hardwood Chip may Confound Research Results. AALAS Scientific Session. -­‐A variety of bedding substrates are commercially available for use in research settings, including hardwood chip, corncob, and various paper-­‐based beddings. While several studies have been done to assess bedding preference in mice and bedding substrates evaluated as far as their effect on the cage microenvironment, little information can be found regarding bedding substrate effect on serum glucose levels and other indicators of metabolism. We compared the serum values of glucose and triglycerides in C57BL/6J mice (wildtype, WT) and mice transgenic for apolipoprotein A-­‐II (ApoAII, on a C57BL/6J background) housed on wood chip bedding versus those housed on corncob bedding after a 14-­‐h (overnight) fast. Both WT and transgenic mice showed significant differences in each serum value based on the type of bedding on which they were housed; those mice housed on corncob bedding showed increased blood glucose levels and decreased triglyceride levels versus those housed on wood chip bedding. This result demonstrates that bedding material, a variable not often considered in research, could have profound influence on the data for many studies of obesity, diabetes, heart disease, or metabolism. Zahorsky-­‐Reeves, J. 2011. The Choice of Bedding Substrate, Route of Blood collection, and Method of Glucose Determination All Affect Fasting Blood Glucose Levels in C57BL/6 Mice. AALAS Platform Session. -­‐This study compared 4 bedding substrates (corncob, paper, hardwood chip, and wire-­‐bottomed cage inserts) and 2 routes of blood collection(lateral tail vein and retroorbital sinus) in 6 male C57BL/6NCrl mice. Mice were maintained with ad libitum food and water on each bedding type for 1 wk, with at least 1 wk of rest on hardwood chip bedding in between sample collection. The night before blood sampling, the bedding was changed for fresh and food removed. Mice were anesthetized with isoflurane for all blood sampling. Blood was collected from bothanatomic locations on each mouse up to 5 times over a course of 4 mo. Samples collected from the retroorbital sinus were analyzed both by glucometer and by chemistry analyzer machine following collection into serum separator tubes. The blood obtained from the tail vein was analyzed for glucose by hand-­‐held glucometer only. Depending on the bedding provided, each mouse showed variability in the blood glucose values, even when the same bedding type was used at 2 different time points during the study. Significant differences in blood glucose were noted between the 2 collection routes on each testing day when analyzed by the hand-­‐held glucometer. Variations in glucose levels were also observed when blood obtained from the retroorbital sinus was analyzed using the hand-­‐held glucometer compared with the machine; these values were not significant across the group, but for some individual mice it approached a 20% difference or more at any one

time point. These results stress the importance not only of consistency in the choice of bedding substrate for any experiment in which fasting glucose values may be important, but also indicating this information as well as the route of blood collection and method of analysis in any published material generated from such work.