Dairy.

Learnt today that the dark patches on many of the cows teats when milking are not always pigment but more often damaged blood vessels with the suction from the milking bits. This is much the same as with us if something such as the hoover is pressed against the arm for a length of time. This does not have an affect on milking performance, instead simply making the teat have dark patches in certain areas.
I also asked today about the process of putting the numbers onto the milking cows rears. This, I was told, is done in a process called freeze branding. This is carried out with number brands being dipped into liquid nitrogen and pressed onto a area on the cows rear that has coloured hair. Then after a while the scab that forms will drop off. The hair that grows back to replace it will grow back white, thereby showing up on the cows coloured rump. This can be a problem when the rump is entirely white, but I was told that the majority of farmers, unless they have a particularly large herd will be able to identify and come to recognise these cows from both their behaviour and their general appearance.