Breeding pairs are failing to produce litters, and separately, labs are unsure whether to keep maintaining a low-use heterozygous colony that requires constant genotyping.

Address fertility failures and idle-colony costs separately: 1) For fertility problems, check health status, handling stress, diet, and light/dark cycle first — ensure an adequate uninterrupted dark period, since some genetically engineered strains simply have intrinsically low fertility regardless of husbandry. 2) For complex or persistently low-fertility models, contact a dedicated breeding service rather than continuing ad hoc troubleshooting. 3) For infrequently used colonies, compare the ongoing cost against cryopreservation: maintaining a heterozygous colony requiring frequent genotyping can run from a few thousand dollars to over $10,000 per year, and this cost compounds over time while cryopreservation is a one-time cost typically recovered through cage-cost savings within months. 4) Design breeding schemes around the genotypes/Mendelian ratios actually required for experiments rather than breeding for desired phenotypes generally, to reduce excess animal production.