We all know who you are. The constant drumbeat on commodity feeds and sulfur are telling. Just waiting on the 'white-eye' claims to resurface...
No, I don't agree; most of your postulations are off-base.
1. Yes, the cow's milk production will be nominal by 5-7 months, but they don't all kick the calf off; I've seen way too many big yearling calves still nursing the cow when she calves the next time - especially in those 'year-round calving' herds.
I'm not overly concerned about the stress of weaning on the COW, though I think it's diminished, compared to abrupt separation. My bigger concern is for that calf that is still building immunity, and will likely be 'leaving' for a new home, where it will be comingled with other calves, all carrying their own 'set' of bacteria/viruses.
The calves with nose blabs aren't 'constantly assaulting' their dams trying to nurse - they're off grazing and doing what they do all day long at that age; they do come back and stand by the cow some, but it's not distressing to the cow.
2.The nose blabs do absolutely NOTHING to promote mastitis. There is no connection whatsoever.
If you think a calf butting a cow's udder causes mastitis...then every beef cow would have it. Have you ever watched an aggressively-nursing calf without a nose-blab? A lot of them are pretty danged rough on the old gals' bags - but they don't develop mastitis.
Minimal to no udder-butting with the weaners, as they can't latch on to a teat to get started.
Sure, the cows will have some udder distension - but no more than they'd have if you just separated cow and calf, or did fenceline weaning.
3. My Procedure: Calves are run into chute and headgate. Nose blabs are inserted. Calves are released back out with their dams for 4-7 days.
After that period, calves are run back through the chute, nose blabs are removed, and the calves are turned into a pasture separate from their dams - usually with yearling heifers separated from the bull and bred cows due to calve in the next season - they're not strangers.
They go right on doing what they were doing before - just not with their dams. If it's spring/summer, they're grazing with the group, if it's fall/winter, they're eating hay and some(gasp!) distiller's grain product with the group. Even with the spring/summer weaned calves, we feed a small amount of distiller's grain just so they know what feed and a feedbunk are.
Most of our calves are in the 6-7 month age range when we wean; typically 450-700 lb, depending on breed, parity of dam, season of year.
Biggest stress - on the calves and ME! - is having to run 'em through the chute twice.
Yeah, it's a lot more trouble than just loading 'em on the trailer on their way to the salebarn - which is how I used to 'wean', when I was doing the no-management year-round calving deal.
BUT, that is not good for the calves, the next fellow buying those stressed non-vaccinated calves, or for the beef industry as a whole.
For many years, Southeastern cattle have had a bad reputation and have been discounted (and rightfully so) because so many of them were this sort of wreck in the making. That's changing some, as producers see the benefits of doing pre-weaning vaccination, weaning and pre-conditioning - and the fact that buyers are usually willing to pay more for calves that aren't going to be so likely to fall apart on 'em a week or two out...
No one is forcing you to use them. They're not for everyone's operation - but they are a proven, valuable aid in accomplishing lower-stress weaning.