My family own an estate in Dorset and we have 4 dairies on the farm and milk about 800 cows We are lucky in that we have a contract with M&S so all our milk is sold to them. This is what we do here and on the majority of farms, as with any industrry you do get the rogues.
Our cows are milked twice a day for 10 months of the year the other 2 months they are what are called dry cows waiting to calve.
When milked they are done morning and evening. They are checked daily for mastitis and if they do have it, they are treated with an antibiotic cream which is put in directly into the udder, a course usually lasts for 7 days and the milk is disposed of (flushed away) for the period of treatment and after until any chance of the antibiotics have been cleared up. The cows have tape around the tail to show which is which.
They do get treated by the vet if they are ill but again milk is disposed of if they are on antibioics.
It is cruel not th treat an animal if it is ill and so I would assume that organic farmers would follow the above practice as well which is just good farming.
Mastitis can be caused by many things, something as simple as another cow treading on an udder, can be inside or outside.
Our cows are housed during the winter, some are in stalls and some are in barns, cleaned out and strawed up daily. During the summer they are out on fields. Dairy farmers tend to produce their own silage which iswhat the cows get fed on mostly during the winter, we also grow maize from them.
As far as I am aware the difference in organic/non organic is the feed. Grass fields have to be treated with organic fertiliser(i.e the cows poo) and the land passed organic by the soil association and any supplementary feed has to be organic as well.
I have never in my life seen or heard of any of our herd or those of farmers I know being injected with hormones.
The milk is collected daily and a sample is taken by the tanker driver and will get tested at the collection dairy.
I think that is about it just off to get DD from nursery but happy to help if I can, we could do sheep next as I keep staring at them in the field as they are wiating to lamb.