the a : icr ( crl : cd1(icr ) ) and b : icr ( tac : icr ) mice were purchased from two different commercial laboratory animal breeding company in korea . the mice were housed in a pathogene - free animal facility under a standard 12 h light / dark cycle , maintained in conventional housing conditions at 221 and 5010% relative humidity . all mice were provided with ad libitum access to standard irradiated chow diet ( purina rodent chow 38057 ) consisting of moisture ( 9.03% ) , crude protein ( 21.52% ) , crude fat ( 5.03% ) , crude fiber ( 4.33% ) , crude ash ( 6.31% ) , calcium ( 1.18% ) , and phosphorus ( 0.35% ) and drinking water . all animal procedures were conducted in accordance with guidelines of the institutional animal care and use committee , national institute of food and drug safety evaluation ( nifds , cheongju , korea ) . phylogenetic trees were constructed using the dnapars program of phylip ( phylogeny inference package ) version 3.695 ( http://evolution.genetics.washington.edu/phylip.html ) based on alignment of snps . seqboot and condense programs of the phylip package were used in bootstrap analysis of 100 resamplings of the data sets . measurement of body and organ weights was made based on the methods of the international mouse phenotyping consortium . hematological analysis was determined using by advia 2010i hematology system with autoslide ( siemens , germany ) . clinical chemical parameters were measured from a single serum sample using a hitachi 7100 automatic analyzer ( hitachi , japan ) . we noticed that korl : icr had a significant increase in the litter size of the second litter as compared with the first litter . therefore , the number of offspring of the first litter was taken as to litter size . time to delivery represents the time period from mating to birth and fertility rate represents a ration between number of female mice giving birth and those used for mating . cages were observed three times per week and the number of pups born dead or alive and the number of pups weaned in each cage was recorded . statistical changes in all data were determined using one - way analysis of variance ( anova ) . the a : icr ( crl : cd1(icr ) ) and b : icr ( tac : icr ) mice were purchased from two different commercial laboratory animal breeding company in korea . the mice were housed in a pathogene - free animal facility under a standard 12 h light / dark cycle , maintained in conventional housing conditions at 221 and 5010% relative humidity . all mice were provided with ad libitum access to standard irradiated chow diet ( purina rodent chow 38057 ) consisting of moisture ( 9.03% ) , crude protein ( 21.52% ) , crude fat ( 5.03% ) , crude fiber ( 4.33% ) , crude ash ( 6.31% ) , calcium ( 1.18% ) , and phosphorus ( 0.35% ) and drinking water . all animal procedures were conducted in accordance with guidelines of the institutional animal care and use committee , national institute of food and drug safety evaluation ( nifds , cheongju , korea ) . phylogenetic trees were constructed using the dnapars program of phylip ( phylogeny inference package ) version 3.695 ( http://evolution.genetics.washington.edu/phylip.html ) based on alignment of snps . seqboot and condense programs of the phylip package were used in bootstrap analysis of 100 resamplings of the data sets . the neighbor program of phylip measurement of body and organ weights was made based on the methods of the international mouse phenotyping consortium . hematological analysis was determined using by advia 2010i hematology system with autoslide ( siemens , germany ) . clinical chemical parameters were measured from a single serum sample using a hitachi 7100 automatic analyzer ( hitachi , japan ) . we noticed that korl : icr had a significant increase in the litter size of the second litter as compared with the first litter . therefore , the number of offspring of the first litter was taken as to litter size . time to delivery represents the time period from mating to birth and fertility rate represents a ration between number of female mice giving birth and those used for mating . cages were observed three times per week and the number of pups born dead or alive and the number of pups weaned in each cage was recorded . statistical changes in all data were determined using one - way analysis of variance ( anova ) . the phylogenetic trees based on distance , the minimum genetic distance of korl : icr and other icr showed a genetic structure with three main clusters ( figure 1 ) . from these distance matrices , one can infer the nature of the identified stock differences and the genetic relationships between them . this indicated that b stock has small genetic diversity compare with a stock and korl stock , and there is large genetic diversity between a stock and b stock . we measured litter size , body weight , body length , various organ weight , hematology and clinical blood chemistry of the korl : icr compared to other icr . mouse phenotype analysis , body weight of korl : icr , a : icr and b : icr has been measured during the designated developmental periods ( 3 weeks to 12 weeks ) . korl : icr and other icr mice experienced similar in body length as well ( figure 2b ) . female korl : icr mice were experiencing a significant increase in liver , heart and kidney weight compared to a : icr , but no difference with b : icr was observed ( figure 2c ) . male korl : icr mice had a significant increase in liver , spleen and testis weight compared to a : icr ( figure 2d ) . the mean litter size of korl : icr mice was 14.52.9 which was higher than commercial icrs ' ( table 1 ) . otherwise , there are no significant differences among the biological phenotypes of korl : icr and other icr . as summarized in table 2 , 3 , some hematological and biochemical parameters have been observed with sporadically significant differences . laboratory mice are the essential resource to identify the potency and safety of the drugs and estimate the potency and adverse effects of drugs during the developing stage . according to the effectuation of the nagoya protocol , laboratory mice are not only indispensable for life science studies but also are being considered as important resource . among laboratory mice , icr mice are most popular outbred mice broadly used in various fields like toxicology , oncology , pharmacology , pharmaceutical products safety test , and etc . . swiss mice , that were crossed in 1926 and then adopted by the institute of cancer research in 1974 ( subsequently merged with commercial production of icr by companies began in 1959 , and the strain was made available to academic and commercial breeders . currently , many breeders worldwide have possessed their own icr stocks and the icr stocks have been reproduced for their academic or commercial purpose . the opinions that there might be possible to have differences among icr mice already ensured in various regions of world which have been raised for long term and among mice of the identical stock bred by different breeders have been proposed in some point of view , but there are not sufficient evidences to support these yet . even though outbred mice are hard to realize the reliability and the repeatability , they are consider to be worked as better resource when the test result is applied to human due to the genetic diversity if compared to inbred mice . in addition , the advantage of using the icr stocks is extremely high in reproduction rate than the other outbred mice so that it may help the study cost effective . every icr breeder has adopted and being bred these following common protocols : maintain icr stocks as long as possible , maintain genetic diversity as possible by composing multiple colonies , and minimize the genetic drift . this study is carried out to establish scientific supports how different in aspect of normal growth curve , breed grad , and clinical blood chemical analysis to ensure the characterization data of icr stock mouse which have been bred by circulation breed approach for more than 50 years . the breed capacity of both korl : icr mice and commercial icr mice were identified . the mean litter size of the korl : icr mice were higher than other icr mice . between monthly litter size and litter size per number of pregnancy of the korl : icr mice did not experience a significant difference , but the size of second and third litter were higher than first and fourth litter ( data not shown ) . the korl : icr mice were having median value of between a : icr and b : icr in a basic phenotype analysis . to tests evaluation of reactivity drugs , their behavioral changes were observed after administering caffeine and chlorpromazine which activates the central nervous system ; it was possible to identify that the recovery rate of the korl : icr was similar to other icr mice ( data not shown ) . korl : icr was deduced that there was no significant difference with commercial icrs , and some weight gaps of the organs might be dependent the breeding condition ( feeds , the breeding place ) . since the comparison studies on laboratory mice have not been remarkably activated , we have faced the difficulty of comparing the study result at this moment . ( 2016 ) suggested that three icr groups , the korl : icr , a : icr and b : icr derived from different sources have an overall similar response of body weight , histopathological structure and inflammation to gastric ulcer inducers . alcohol induced ulcer model comparison assessment for reviewing the characteristics of the korl : icr were having similar result . however , the result would be more appropriate to compare with control group rather than the comparison of the absolute value because of a significant difference in certain enzymes . another implication of the study is that references data ( breeding rate and basic phenotype ) regarding the korl : icr are secured and can be shared with the other researchers . the korl : icr stocks have been used for decades in terms of conducting lot release project and more , in the national institute of food and drug safety evaluation . in conclusion , we will study secure general documents needed to have as mice resource through this accumulation of various experimental data .
mouse is a commonly used animal in life science studies and is classified as outbred if genetically diverse and inbred if genetically homogeneous . 
 outbred mouse stocks , are used in toxicology , oncology , infection and pharmacology research . 
 the national institute of food and drug safety evaluation ( nifds ; former the korea national institute of health ) have bred icr mice for more than 50 years . 
 we investigated to provide users with information and promote accountability to the korl : icr . to secure 
 the indigenous data , biological characteristics of korl : icr were identified by comparing with other icr stocks . 
 this domestic icr stock was denominated as 
 korl : icr. phylogenetic analysis using snps indicated that the population stratification of the korl : icr was allocated different area with other icr . 
 in addition , we measured litter size , body weight , body length , various organ weight , hematology and clinical blood chemistry of the korl : icr compared to other icr . 
 otherwise , there are no significant differences among the biological phenotypes of korl : icr and other icr . 
 these results suggest that as a genetically indigenous source colony , the korl : icr is seperated ( or independent ) stock with other icr . also , we confirmed that there is no difference among the korl : icr and other icr on biological phenotypes . 
 therefore , the korl : icr source colony might be a new stock in distinction from other icr , it is a good milestone in securing ownership of the national laboratory animal resource . 
 the nifds expects that the korl : icr mice will be useful animal resource for our domestic researchers .