Good for you.
Now i have another theroy sort of for you.
In the one thread you stated that if this animal made it; it would stay on the farm for a very long time.
I am not suggesting you spend more money on this calf, that is up to you. So i am going to draw on experience and what you have said to offer a suggestion. That suggestion would be...this calf spend as little time on your farm as humanly possible. If you sell it after it gets better, watch the withdrawal times. Please note that if this were my calf it would never be sold to some other unsuspecting buyer. And if i decided to keep it to butcher at a young age it would be so isolated that no other animal new it was there...not possible so I would...____________feel free to fill in the blank.
REASONS:
1. quite possibly this calf is either PI or it was exposed to the virus at some stage before you got the calf and is infected.
(a) senario 1 PI calf...
this calf will always be a poor doer. Will alway require some source of drug treatment at stages of it's life. This drug treatments will occur when the calf is stressed. Stressed by sudden weather changes or storms. Stressed by moving to a different pasture. Stressed by an aggressive or "bullying" animal, stresssed by weaning. Stressed by change in feed.
As well if this is a PI animal it will shed the virus at any time, more when stressed out of every openning in the body. Mouth, nose, eyes, pee-er, pooper. It will spread the disease everywhere, decreasing the threshold of resistance of the healthy animals (more on that in a bit) You will be compromising your other animal, and if you have breeding stock, you will be compromising your unborn animals.
(b) senario 2. This calf was exposed at the sale barn and the disease is manifesting itself now. Chances are it will die due to the stress on the body, and considering the poor health it is in. If it does not die soon, it more than likely will die in the feedlot or pasture. BUT not before infecting alot of other animals and your unborn animals. This animal if it does make it will always be a poor doer and a costly animal in feed and drugs to keep condition
Now on to the disease threshold thing:
Lets make some asumptions. Lets base these asumptions on a perfect world in the bovine world. Lets base this on you having cow calf pairs as well as a buyer of calves. I do not know if you breed and calve your own, but I will make the assumption you do. At the very least, you are a buyer of calves at a dangerous point in the immune stage (NO disrespect intended)
Assumptions:
1. All mothers of any calves were pre bred vaccinated properly without any degrading of any vaccine
2. All calves recieved timely colostrum, within the first two hours.
3. All calves were born in a stressfree enviroment. Stresses include, weather, dumping in a snow bank, hard pull, difficult calving, poor mothering etc.
Please keep in mind that all these stressses reduce the amount of IgG absorbed in passive transfer. As well if the vaccines were poorly administered that would reduce the protection of the unborn, as well as the amount of IgG in the colostrum.
So assume this new born calf ( named Jed) had 100% passive transfer and is ready and raring to go.
Now lets add in your surviving calf that remains on the farm to the senario.
Jed is out in the world wandering around with it's momma. It had 100% protection Lets give it 100 points of resistance to disease...the threshold
In comes a storm with snow or rain, a cold rain, it places stress on the threshold and loweres it by 5 points
Momma and calf are separated because of the storm, the calf does not get one meal due to hiding from the rain or snow threshold is lowered by 5 more points
2 other calves come down with a slight touch of scours, thanks to the weather, and a slight failure for 100% passive transfer. So they are shedding say rotovirus...increases the stress on the immune system, again lowers the threshold resistance by 20 points.
Your calf, the one you have just been treating like mad to save it'slife, has been shedding the virus all the time, reduce threshold by another 10 points
Your calf is under stress because of the weather, his pathogen level jumped and is now shedding more than normal reduce by 30 points.
All cows are carriers of the scour viruses at all times, the are affected by the weather and start shedding the virus at a higher than normal rate reduce threshold by another 5 points.
Jed is now down to 20 points of threshold resistance. That is all that stands between him and the disease your calf is shedding all year round. It is going to take a near three to four weeks before the immune system is back up to 100% because it has been taxed so much. Jed's immune system has been taxed to the point that he gets a slight touch of scours, then he gets a slight cough, then his temp rises, he now has no immunity to fight of BVD or IBR or anything else. He is fair game to any disease on your farm.
Is it worth it to keep this first calf who has been so sick? Remember Jed had 100% passive transfer (PT). What about the ones that did not? What about the ones that you buy, that you can not guarantee that the pre breeding vaccines went off without a hitch, or that they got 100% PT. What happens to the rest of your animals if you keep a PI or a sale barn infected animal on your farm?
I know the assumed senario is worst case, and that not all animals get sick, but...is that a risk you are willing to take?
Only you can judge that.
RR