Bacterial composition of goat milk and its relations with somatic cell count during lactation

An increase in somatic cell count (SCC) usually indicates poor udder health and possible mastitis, although, in goats, SCC is not always related to an infection. The Norwegian dairy goat industry has observed an increase in SCC during the summer mountain pasture. Other causes than bacterial infection might be at the origin of this problem and, to get a better overview, this study aimed to investigate the milk composition, the goat milk microbiota, and changes in bacterial counts in one herd over on lactation period and to correlate these observations to the level of somatic cells. Forty goats were sampled monthly during lactation from March to October, including the pasture period (June to August). Amplicon sequencing of the 16S gene was used to study microbiota changes. The presence of mastitis-related species in the microbiota data was then correlated to the SCC. A positive correlation was detected between the bacterial count and SCC, and each sequence variant was correlated to a specific genus of bacteria. Among the bacteria present in the samples, some of the sequence variant (SV) showed a correlation between each other. Interestingly, when the correlation was studied within each month, some months showed a positive correlation between somatic cell count and bacteria count (or some SV), while others did not show any correlation. This study highlights some of the relationships existing between bacterial count and somatic cell count in goat milk and their influence on the milk microbiota composition.