Somatic cells and bacteriological examination of milk samples of goats

Mastitis, mainly caused by contagious bacteria, is an important disease in dairy goat production, especially subclinical mastitis. The aim of the research was to study the relationship between somatic cell count (SCC) and presence of mastitis pathogens in goat milk during the period 2022-2024. A total of 987 udder-half milk samples were obtained from 5 goat farms in Slovakia. The presence of pathogens was determined by bacterial cultivation and grown colonies were identified by MALDI-TOF MS at the species level. Fossomatic 7 was used to determine SCC. To evaluate the frequency distribution of the samples, the following groups of SCC were considered: SCC1 < 500 × 103 cells/ml, SCC2 ≥ 500 < 1 000 × 103 cells/ml, SCC3 ≥ 1 000 < 2 000 × 103 cells/ml, SCC4 ≥ 2 000 × 103 cells/ml. The individual milk sample were 42.2% in SCC1, 17.0% in SCC2, 16.7% and 24.0% in SCC3 and SCC4, respectively. Of the total number of samples, 23.0% were bacteriologically positive. The most frequently identified pathogens were Staphylococcus spp., especially non-aureus staphylococci and mammaliicocci (NASM). Among the NASM, Staphylococcus epidermidis (40.3%), Staphylococcus caprae (27.5%) and Staphylococcus simulans (10.4%) were the most prevalent species. Only 2 samples were positive for Staphylococcus aureus. A higher occurrence of pathogens was identified in SCC ≥ 1 000 × 103 cells/ml (SCC3 and SCC4) compared to SCC < 1 000 × 103 cells/ml (SCC1 and SCC2). However, approximately 34.8% of uninfected half udders with no bacteriological findings had SCC ≥ 1 000 × 103 cells/ml. In conclusion, NASM were the most common bacterial causative agents of subclinical mastitis in goats and it is not easy to set a specific SCC for subclinical mastitis diagnosis as it is in dairy cows.