Trio Breeding Scheme Planner

Trio Breeding Basics

One stud male housed continuously with two breeding females in the same cage. The male services both females; the females cycle independently and produce offset litters.

A trio occupies one cage but produces ~50% more pups per cage per month than a monogamous pair. Cage cost, husbandry time, and per-diem charges scale with cage count, so trios are ~50% more cost-efficient per pup.

• Two dams give birth on the same day → litters compete for milk, mortality climbs
• One dam dominates and stresses the other → poor breeding from the subordinate
• Male is too young or too old → lower fertility
• BALB/c males that fight when introduced to multiple females

Switch to monogamous pairs for any of these.

The Yield Equation

The full pipeline from breeding pair to usable weanling has three loss factors:

Only a fraction of pups have the genotype you want. For het $\times$ het → homozygote, that's 1/4. For dihybrid → double homozygote, that's 1/16.

Of all pups born, some die before weaning. C57BL/6J runs ~85%; BALB/c runs ~75%; CD-1 runs ~90%. The dead pups don't make it to genotyping.

PCR fails on a few percent of samples (poor DNA, contaminated tubes). Default is 95% — i.e., 5% of weanlings need re-snipping or are lost from the count.

For a het $\times$ het cross on B6 with default genotyping: 0.25 $\times$ 0.85 $\times$ 0.95 = 0.20. So you need ~5 pups born for every correct-genotype weanling — and that's before the breeding-failure buffer.