The researchers tested a special extender made of fatless milk, glucose, and antibiotics to preserve the viability of cooled canine semen for up to 48 hours in a transport container. The study involved different breeds of stud dogs from Niteroi and Rio de Janeiro, with good quality semen collected and evaluated. Results showed that the extender allowed the semen to maintain good quality even after 48 hours, making it suitable for overnight delivery after cryopreservation at 4°C.