What breed of cattle are they?
I really doubt those defects are from weeds or Pine trees. We have pine trees on much of our ranch, so I have had some experience with Pine tree abortion before restricting cattle from those locations in late pregnancy. I have never heard of defects like those pictured from Pine trees. Abortions and weak calves that don't survive are the usual consequence when certain animals consume the needles.
If this is an inherited recessive defect your cow has a 50% chance of being a carrier if that bull is her sire. Since the cow that had the defective calf would also be a carrier, it would appear there are at least two carriers in that small herd, so your cow could be a carrier even if sired by a different bull. Breeding your cow to another unrelated bull would eliminate your chance of seeing the defect in her offspring, as long as the bull you choose is not also a carrier. If she is bred to another carrier, she has a 25% chance of producing an affected calf. The real problem is that half of her offspring are also carriers. If you keep her daughters you will continue to increase the number of carriers in the population. As the number of carriers increase in a population, the likelihood that carriers are mated to each other increases. You may have the opportunity to identify and stop a problem now. If the defect could be identified and a test developed to identify the carriers, you would be able to easily determine whether your cow or others, are carriers.
Send the pictures and information to Doctor Beever. Even though they are not your cows, the fact that you have a breeding animal from this small herd gives you the right to some piece of mind. He may be too busy to respond or he may not feel it needs a response, but at least you will have tried. It is possible there are others out there seeing similar calves. If that is the case, this could be the chance to identify the genes responsible so others don't need to suffer the same consequences.