## 2 Materials and Methods  
### Study Area--Milk Samples  
Sampling took place in the rural area of Epirus region and in western Greece, and more specifically in the regional unit of Arta and Preveza (Epirus) as well as in Amphillochia in the regional unit of Aitoloakarnania. Dairy farmers were identified with the collaboration of the regional Veterinary agencies. These areas, where the current survey took place, are mountainous with intense slope differences and a rather poor road network. The distance of many farms from the capital of the area is more than 70 km. In these areas two types of farming are observed and we classified them as Group A farms and Group B farms.  
The characteristics of each type of farming are analyzed as follows:  
Group A: This is the group of more \"intensive\" breeding. Most of the animals are sheep belonging to Frizarta breed or to Karagouniko breed or to various cross breeds but mainly Boutsiko with Frizarta (25%). The caprine population did not exceed 5% of the herd population while the average size of the herd varied between 250 and 400 animals. Milking was performed with the aid of milking parlours. The animals were housed and they usually grazed for some hours daily on pastures adjoining the unit. They were fed supplements of concentrates and hay. Sheep energy requirements in this system were estimated to be supplied 53% from grazing and 47% from supplementary feeding (of which 41% concentrates and 6% roughage). The respective values for goats were 73% from grazing and 27% from concentrates.  
Group B: This is the group of more traditional farming practices. In these farms the majority of the animals belonged to cross breeds mainly between different local mountain sheep breeds or in some cases with Karagouniko or Frizarta breeds. Caprine population belonged to indigenous breeds (_Capra Prisca_) and reached 10% of the herd while the average size of the herd varied from 75 to 150 animals. More than 75% of these farms were located in high altitude remote areas. Milking was performed manually. The animals were housed during the night, they were grazing all day long in pastures located in the surrounding area of the holdings, receiving a small amount of concentrates at dusk.  
It is self-evident that these characteristics of the two groups of farms were shaped over time by various factors among which the most important was the exact geographical location of the farm (the more remote, the more traditional).  
In both groups milling took place twice a day and the milk was placed in cooling bulk tanks with temperatures adjusted to 4-6 \({}^{\circ}\)C. Each farm had its own bulk tank.  
From each group 20 farms were selected randomly and samples for the purposes of the present study, were collected in the morning and contained the milk from the milking of the last 12 h. The main criterion for a farmer to be included in the current survey was his ability to understand the purpose of this study and his willingness to participate in the survey.  
Samples were collected throughout the milking period, that is from March till August 2020 (1 sample per month from every tank, 6 samples in total from every tank). 1000 mL of raw unprocessed milk were collected aseptically into sterilized containers. All samples were transported in isothermal boxes with ice and within 2 h from the collection were subjected to the laboratory in the Department of Agriculture, in Arta.  
The overall workflow for samples collection and analyses performed is presented in Scheme 1.