Variation of microbiota, chemical composition and B-vitamins in milk from alpine pasture and indoor dairy cows

The aim of this study was to investigate the variation of milk microbiota during and after summer transhumance in relation to milk composition and B-vitamins content. The project involved 26 Italian Simmental cows (5-7 per farm) reared in a 4 permanent farms (PF) located at Levico (Trentino, Italy). The cows were moved in mid-June on 4 summer farms (ALP) located at Passo Vezzena (Trentino) and moved back to PF in September. The animals were monitored and sampled in July and October. Milk microbiology plates count with different culture media; isolation and species characterization by 16S rRNA amplicon; microbiota composition by Miseq Illumina and QIIME2 and B-vitamins content (Thiamine, Riboflavine, Nicotinic acid and Folic acid) were performed for each milk sample. The data were analyzed with a mixed model including the fixed effects of herd, period and their interaction, and the random effects of individual cows nested in the herd and of residual. Identified bacteria taxa were classified into two favourable categories: Pro Dairy (LAB) and other Probiotics, and two unfavourable categories: Spoilage and Pathogenic bacteria. The results revealed variability among farms, especially one farm had opposite trend in almost all the traits. Milk composition traits mainly showed higher values after the transhumance, and significant interaction among herds for some traits. LAB category has significant different value in PF than ALP. Other Probiotic was higher during ALP. Similar trends were observed in Spoilage and Pathogenic categories. The B-vitamin complex showed higher values, except for Folic acid, during summer pasture than indoor feeding, with small differences among herds. The metagenomics analysis confirmed the high variability of the milk microbiota during and after summer transhumance. Moreover, we observed a large influence of different herd management on milk microbiota variation. The research was a co-funded PhD by Fondazione Edmund Mach and University of Padova.