Estimation of individual somatic cell counts using single nucleotide polymorphisms from bulk milk samples

The SCC of individual cows plays an important role in the assessment of udder health. Until now, individual milk samples have been required to determine the SCC of each cow. This study introduces a novel measurement method that uses the genetic information of individual cows to identify them within a shared bulk milk sample. The Genocells method applies DNA chip technology and genotyping data originally generated for breeding purposes. Using this approach, individual SCC values for all cows in a herd can be estimated from a single bulk milk sample. The first part of the study investigated how many bulk milk samples are required to obtain reliable individual SCC estimates. In the second part, results obtained with the Genocells method were compared with SCC values from individual milk samples collected during routine monthly milk recordings. The Genocells method showed no significant differences in an intra-assay comparison, in which 10 samples from the same bulk milk were analyzed. When compared with SCC results from individual milk samples, significant differences were observed only when SCC values were below 100,000 cells/mL. Overall, Genocells results showed a strong correlation with individual sample results, with 81.5% of values assigned to the same SCC class as those obtained from individual milk samples collected on the same day. Because of the substantially reduced sampling effort, the Genocells method represents a promising approach for monitoring individual udder health in dairy herds. The ability to derive individual SCC values for all cows from a single bulk milk sample constitutes a clear advantage over conventional methods that rely on individual sampling.