Generally an inbred strain produced in a Barrier Unit colony is assigned a room or location where it is the only strain of a particular coat color produced in that room. Unfortunately, separation of all strains by coat color is not always possible. One of a number of examples is production of F1 hybrids that requires the use of two similarly colored strains as the inbred parents. Because Taconic prohibits barrier-to-barrier transfers for health reasons, both BALB/cAnNTac and A/JCrTac strains must be produced in the same Isolated Barrier Unit (IBU) to produce the CAF1 hybrid. All three of these models are albino, so genetic monitoring plays an especially important role in situations such as this.
Absolute protection for this type of risk is impossible to achieve without testing every same-colored mouse in the room. However, statistical sampling of the population can provide a high degree of confidence that no mix-up has occurred. In situations where similarly colored strains must be raised in the same production locations, standard operating procedures dictate specific rules for frequency of monitoring and also for how to select animals for monitoring. For example, if two albino strains are housed in the same barrier, Veterinary Services personnel develop a monitoring schedule that is based on Production data of the number of new matings set up. Monitoring is done on a number of animals from that strain that is equal to 20% of the number of new matings set up in that two-week period. Barrier personnel select as many animals from that strain to satisfy the scheduled number for that cycle; each animal selected must be a first-litter pup from a breeding cage that has not been sampled previously. This type of Production Genetic monitoring continues biweekly as long as there are similarly colored animals in that location. Historically, animals were tested for subsets of biochemical polymorphisms that would allow discrimination between the strains. Presently, we employ a two-microsatellite marker panel that is unique to each strain bred at Taconic.
We typically do not perform genetic monitoring of this type on Taconics rat strains, as no two similarly colored rat strains are housed in the same barrier location. We do, however, always monitor incoming inbred-rat transfers into barriers from our Gnotobiotic FC and PEC colonies, as described.
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