Not been around much recently, but thanks to all your advice I was able to help one of the cows which looked poorly a couple of weeks ago. He'd been limping around for a while - then seemed to get better. Then one morning I heard "mooing" at 5:30am so I looked outside and they were just getting up - they'd spent the night in their field immediately outside our back garden. I noticed a small brown one unable to walk, with his front right leg hanging limply, and whenever he tried to walk using the front left leg that one buckled under him, and he fell! I watched this for half an hour and it was worrying me terribly, but my partner wouldn't let me call the farmer at such an early hour - blimey doesn't he realise they work long hours! Anyway, when I came home from work the cows came back into this field again and one was missing - yes, it was the little brown one. So I rang the farmer, apologised and hoped he didn't think I was interfering - thinking if he'd been and seen his cow limping he may have taken it away. He told me he'd noticed this cow's shoulder kept dislocating, but we were worried where this cow may be. He and his father (also a farmer) came straight up and found the little cow in the next field, checked it out, then left it. But the following afternoon when I returned home, there were four farmer's in the field trying to catch this little cow, then they took it away.
So thank you to everyone who suggested I inform the farmer if anything appears to be wrong with any of his cows. He told me I wasn't interfering and thanked me for calling him.
I still love those cows to bits - even Bull Man (as I've now called him because his neck is huge) as he's as soft as a brush. Mind you I don't think he'll have fathered any little ones as he's sooooo laid back and docile, and never seems to be at all interested in the three girlies in his field! Time will tell ...