MALDI-TOF mass spectrometry profiling of bovine skim milk for subclinical mastitis detection

Abstract

IntroductionMastitis is one of most impacting health issues in bovine dairy farming that reduces milk yield and quality, leading to important economic losses. Subclinical forms of the disease are routinely monitored through the measurement of somatic cell count (SCC) and microbiological tests. However, their identification can be tricky, reducing the possibilities of early treatments. In this study, a MALDI-TOF mass spectrometry approach was applied to milk samples collected from cows classified according to the SCC, to identify differences in polypeptide/protein profiles.Materials and methodsTwenty-nine raw milk samples with SCC >200,000 cell/ml (group H) and 91 samples with SCC lower than 200,000 (group L) were randomly collected from 12 dairy farms. Spectral profiles from skim milk were acquired in the positive linear mode within the 4,000–20,000 m/z mass acquisition range.Results and discussionBased on signal intensity, a total of 24 peaks emerged as significant different between the two groups. The most discriminant signals (4,218.2 and 4,342.98 m/z) presented a ROC curve with AUC values higher than 0.8. Classification algorithms (i.e., quick classifier, genetic algorithm, and supervised neural network) were applied for generating models able to classify new spectra (i.e., samples) into the two classes. Our results support the MALDI-TOF mass spectrometry profiling as a tool to detect mastitic milk samples and to potentially discover biomarkers of the disease. Thanks to its rapidity and low-cost, such method could be associated with the SCC measurement for the early diagnosis of subclinical mastitis.

Extracellular vesicles miRNome during subclinical mastitis in dairy cows

“…As previously described [23], a total of 120 primiparous Holstein Friesian cows belonging to 10 dairy farms located in the provinces of Cuneo and Turin (Piedmont Region, Northern Italy) were selected. Animals were managed according to the local farm production practices.…”

“…The resulting dataset was characterized by an average SCC value of 357,220 ± 1,102,894 cells/mL, 138 ± 87.9 (average value ± sd) days in milk (DIM) and 15,8 ± 4.2 kg of milk matter avarage production. Moreover, 17/60 (28.33%) samples were positive to Staphylococcus spp., 2/60 (3.33%) were positive to Streptococcus uberis, while the remaining samples (41/60, 68.33%) had negative bacteriological tests [23]. Before sequencing, samples were clustered using a SCC threshold level of 200,000 cells/mL, normally considered as a SCC level of subclinical mastitis, in two groups high SCC (group H) and low SCC (group L).…”