The species spectrum of milk microbiota in healthy cows and animals with mastitis has differences

Mastitis remains the most common disease of cows in countries with intensive dairy production, despite various programs for the prevention and control of infections in animal husbandry. Numerous studies have shown that the acute form of mastitis occurs in 10-25 % of animals, and the occurrence frequency of the subclinical form reaches 50 %. The etiology of mastitis is extremely diverse. Pathogenic and opportunistic pathogens can include indigenous microbiota, but, as a rule, bacteria enter the teat canal of the mammary gland during its exogenous infection. The methodologies and results of studying the microbial spectrum of milk of healthy and sick animals vary in the results of different research groups. In the presented work, the microbiological method was used to evaluate the microbial profiles of milk from healthy cows and cows with mastitis, the dominant pathogens of mastitis and some of their biological properties were determined, and within a separate task, an analysis of microbial diversity was carried out using gas chromatography-mass spectrometry (GC-MS). Healthy cows and animals with mastitis (with the clinical form of the disease) were selected from a large agro-industrial complex (Perm Krai) specializing in raw milk production. Holstein cows ( n = 45, tethered housing) aged 2-5 years differed in physiological status (dry period, I, II and III phases of lactation). Bacterial contamination of the studied samples from cows with mastitis and healthy animals was 100 %. The most common, both in monoculture and in associations in both groups, were bacteria of the genus Staphylococcus and Escherichia coli . Escherichia were significantly (p 0.05). However, the assessment of microbial diversity by multidimensional nonmetric scaling showed that in samples from healthy animals the species composition of microorganisms varied significantly, while mastitic cows it was similar. In addition, the degree of microbial diversity of milk among healthy animals decreased in later phases of lactation. GC-MS method revealed the dominant causative agents of mastitis, E. coli and members of the genus Staphylococcus , as did the bacteriological method, but their shares in the total microbial spectrum were insignificant nad not exceed 0.16 and 2.50 % in dry mastitic animals and 0.35 and 2.05 % in lactating mastitic animals. Considering the numerous functions of microorganisms in the biotope and probable role of the indigenous microbiota in the pathogenesis of mastitis, we believe that the GS-MS method can be used at dairy farms, allowing for the full microbial profile of the udder secretion to characterize animal health conditions. Thus, the bacteriological method is more advisable for studying epizootic conditions at livestock farms and ongoing microbiological monitoring, while the GC-MS method can be used to assess the quality of products and in prognostic studies.