Mastitis, inflammation of the mammary gland is one of the most common diseases in dairy cattle and the main reason for using antimicrobials. The disease is chiefly caused by bacterial infection, and a wide spectrum of bacterial species from masticated milk has been isolated. However, conventional methods of bacterial isolation (gold standard) are only aimed at a few bacterial pathogens believed to cause mastitis and approximately 25% of milk samples from clinical mastitis obtain negative culture results.

Metagenomic studies have led to the description of an entire community of different bacteria present in the healthy bovine mammary gland, which until recently was thought to be sterile. These results have given rise to the theory that a healthy udder is inhabited by different microbiota, and dysbiosis (disturbance of the normal microbial community balance) is now proposed as a possible mastitis predisposition factor.

Furthermore, colostrum (the first food received by the newborn calf) is what most quickly influences the health of its intestines. However, colostrums quality is only defined by nutritional composition and IgG concentration without taking into account the composition of immunity cells and microbiota.

According to the hypothesis that changes in microbiota composition and diversity of the udder may on the one hand lead to the onset or progression of mastitis, whereas on the other these changes may negatively affect the development of intestinal microbiota in their descendents, thereby increasing susceptibility to infectious diseases in their early stages of life, in this project we will be characterising bovine milk microbiota during the different stages of lactation (prior to desiccation, colostrum, milking) and calves’ intestinal microbiota. This longitudinal analysis will cover the entire milking period and is characterised by the dynamics of the bovine udder microbiota in different situations (mastitis condition, parity, and antimicrobial therapy).

The calves’ intestinal microbiota will be compared to their mothers’ microbiota and colostrum immunological quality, with research into the susceptibility of calves to infectious diseases.

Lastly, the milk resistor will be characterised to research associations between consumption of antimicrobials and abundance of different types of resistance genes in the milk. The project will improve our comprehension of the importance of the milk microbial community profile in the development of mastitis and calves’ health.