You can consider weaning the calf when it's 6 months of age or more. How long after she's bred that you can wean the calf off her depends on how long after she calved you had her bred. If you had her bred about three and a half months (~80 days) after she calved, then you should consider weaning the calf two-and-a-half to three months after she's been bred.
When she is too thin, too old, or ill. A cow doesn't really lose her fertility, it just decreases.
When she's dead or becomes very ill that renders her infertile. There's a fair few cows that can still produce calves when they're well into their 20's, depending on how healthy they are.
A cow will often make it's calf stop nursing by the time it's around 10 months of age. Most producers have the calves stop earlier though, like around 3 to 6 months of age, to prevent the calf from "pulling down" his mother any more than she needs to be before she calves again.
Disease or a blockage in the gut will cause a calf to stop eating. This is something you need to take up with your local large animal veterinarian immediately if you wish to have a hope of saving the calf.
First make sure if the calf is indeed nursing from the wrong cow. Then separate the calf and his mother into a different pen or pasture and let them stay in there for a few weeks. Make sure it's just the pair that's in there and there's no other cows in there with them that the calf may decide to latch onto.
She stopped nursing in 1897.
when their done nursing. it's obvious.
Groundhogs usually stop nursing and are on their own at five or six weeks of age.
First stage is when she's a calf. She subsists on her mother's milk for 6 to 10 months before weaning. For bottle calves, they are on the bottle or bucket for around 3 months. Second stage is when she is deemed a heifer, after she has been weaned from her milk source and is able to eat forages on her own. This is her growth period that allows her to reach puberty and the adequate body weight for her to be bred. During this stage she is bred at 15 months, then has her calf at 24 months. While still caring for her calf, she is still growing. Stage three is when she officially becomes a cow after weaning her first calf and her growth comes to a stop when she is deemed mature. Cows often live on average for about 10 years, some twice as long; dairy cows twice as short before being culled out of the herd to be slaughtered for meat.
6 months
about 8 months
No because if they did the babies they are nursing would most likely die of starvation.
It'll go a lot quicker if you get in there and pull the calf out as fast as possible. Backwards calves, in most cases if you see it happening, should be pulled ASAP. Don't wait for the cow to do it, because it the calf has no space to breath if the cow decides to stop pushing and take a rest. You MUST get that calf out immediately so it can live and breath, otherwise you will end up with a stillborn calf on your hands.
At around 5 years old.