On the lines of colostrum...
it takes about three months of good nutrition to build a good quality colostrum (if memory serves). that is if the cow has not been under any previous stress like drought or flooding.
Colostrum also is inhibitied in Passive transfer or reduced in passive transfer if...
- a hard or stressed birth
- inclement weather while calving
- slightly weakened calf due to weather, nutrition, or birthing stress.
might be a good idea to check back on the birthing of these calves and see what was up when they were born and the few months leading up to it.
On another note, cows coming out of a year of hardships like drought and flooding from the previous year might still be trying to play catch up on the nutrition and health. It takes time for cows to recover from these weather related stresses, even in they are in good body score.
We have seen where it takes cows near a year and a half to recover fully from these stresses...unless they are open at some point. The reason I say a year and a half is because they are always working. They are either getting ready for breeding while raising a calf, bred and raising a calf at foot, or bred and just gone through weaning. So when they have to regain their "internal balance" they are not just doing it for themselves, but also for the calf inside and or at foot.
Here is another thought on these summer pnemonias...
...could be a secondary infection that is showing up during times of weather stress brought on by either being a PI calf are infected with BVD.
Can you trace back a few years and see if the same cows or line of cows are producing these sick calves?
You might be on a vaccination program, but when vaccines are left in the sun or mixed to early or got to warm, the vaccines can become inert.
Just some random thoughts
