Introduction: The aim of the study was to investigate the presence of human papillomaviruses (HPV), mouse mammary tumour virus (MMTV), Epstein-Barr virus (EBV), and human polyomavirus BK in canine mammary tumours (CMTs) and to correlate the results of histopathological classification with the results of virological examination. Material and Methods: Eighty CMTs and ten normal canine mammary gland samples were evaluated using histopathological methods and TaqMan real-time PCR analysis. Results: The results indicated that all mammary tumours and normal mammary tissue samples were negative for HPV16 and other HPV, EBV, human polyomavirus, and human mammary tumour virus strains. Conclusion: Further studies should be performed to investigate the existence of other strains of HPV, EBV, and human polyomavirus in CMTs.

The objective of this study was to develop a technique for carrying out repeated biopsies of the mammary gland of lactating dairy cows that provides enough material to monitor enzyme activities and gene expression in mammary secretory tissue. A total of 16 Holstein cows were subjected to 4 mammary biopsies each at 3-week intervals for a total of 64 biopsies. A 0.75-cm incision was made through the skin and subcutaneous tissue of the mammary gland and a trocar and cannula were inserted using a circular motion. The trocar was withdrawn and a syringe was plugged into the base of the cannula to create a vacuum for sampling mammary tissue. To reduce bleeding, hand pressure was put on the surgery site after biopsy and skin closure and ice was applied for at least 2 h after the biopsy using a cow bra. The entire procedure took an average of 25 min. Two attempts were usually enough to obtain 800 mg of tissue. Visual examination of milk samples 10 d after the biopsy indicated no trace of blood, except in samples from 2 cows. All wounds healed without infection and subcutaneous hematomas resorbed within 7 d. There was no incidence of mastitis throughout the lactation. This technique provides a new tool for biopsy of the mammary gland repeated at short intervals with the main effect being a decrease in milk production. Although secondary complications leading to illness or death are always a risk with any procedure, this biopsy technique was carried out without complications to the health of animals and with no incidence of mastitis during the lactation.