Only give Oxytocin when it's necessary, don't give it just because you can. You should really talk to your vet about this, and consider selling off the cow if she can't produce milk for her calf. You'll have to bottle-feed the calf yourself if Oxytocin won't be enough to help the cow give enough milk for her calf.
So please, do your animals a favour and talk to your local large animal veterinarian.
When she is obviously having troubles pushing out her calf, or, she's not progressing any further in her efforts to push the calf out of her after some time.
Cows are mature female bovines that are capable of having calves. By "having" I mean that they are able to conceive, grow and give birth to live young. Gestation is just a fancy term for pregnancy, which also means that a cow is capable of being pregnant with a calf (being the fetus) inside her. Thus, gestation has pretty much everything to do with a cow. If she cannot conceive and become pregnant with a calf in both dairy and beef operations, she is deemed unworthy and culled for slaughter. In order for a dairy cow to produce milk she must both conceive, stay pregnant and give birth to a live calf in order to be deemed productive AND produce milk. For beef cows, the determining factor that enables them to stay in the breeding herd are the calves they are able to produce. They MUST conceive and give birth to a live calf in order to be deemed productive, otherwise she's better off as hamburger.
You are the one who has to keep milking her if you want to keep getting milk from her after her calf dies. Otherwise, she will begin to dry up after a few days and be completely dry after a couple weeks.
Yes. A polled beef cow that is more than likely heterozygous for the horned gene, and the sire that could have been horned or also heterozygous for horns is more than likely to produce a horned calf.
No.
You will have to bottle feed the calf. This sometimes happens with first-calf heifers, probably because the heifer is too small or the calf is too big. Depending on how big the calf is, you will have to separate the calf from the heifer and try to get it to accept the bottle. Start by cornering the calf and have a bottle of milk replacer and dribble some on its tongue, or wet your fingers with the milk and moisten the calf's nose and mouth with it, eventually let the calf suckle on your hand to get it to taste. Replace your hand with the nipple of the bottle. If the calf starts suckling, good! If not, keep trying and don't give up. Keep in mind the calf is hungry, but also keep in mind the calf is used to suckling from momma by now and the bottle isn't something that means "food"...yet. There really is no way to get her to produce more milk as she is young, and probably of the breed type that doesn't produce much milk at that age anyway. You'll have to work with the calf to get it back to health, but still let the calf nurse to keep that bond alive.
Genetics. The genes in the momma cow combine with the genes from the calf's sire to create a calf with either the same colouration of the cow or not. What breed the calf's sire matters to. For instance, a Hereford sire bred to an Angus cow results in a black-baldy calf. Or, an Angus cow that has a recessive gene for Red colour and is bred to either a Red Angus bull or a Black Angus bull also with a heterozygous gene for the red gene can most likely produce a red calf. And the examples go on.
Absolutely NONE. Do not give any pain meds to a calf if it does not need it.
give birth to a calf.
Please check with your local large animal veterinarian for details on what's best to give the calf. You didn't give enough symptoms or details of the calf's condition to get any relevant answers, since there are over a 100 things than can make a calf suddenly stop eating and make it sick.
Only a general overview of the infectious agents for calf diarrhea is included here.
Of course it is! They do it all the time! Dairy cows that are pregnant still give milk until a couple months before they have to give birth again, and beef cows that get pregnant a couple months after giving birth to their last calf (which they're still suckling) still give milk until their calf is weaned at around 6 to 10 months of age.