Thank you for the additional information on these wee ones.

As I am sure you can appreciate the clinical signs you are mentioning are vague, in the sense that they cannot be used to pinpoint one single causative disease agent. Instead there are a range of conditions that we must consider in calves with sudden progressive paralysis/paresis of the hind legs. And since you have said they don't appear to have a great deal of feeling,this does suggest that there is progressive sensory loss, which is a poor prognostic indicator for animals in this condition.

Since we have more the one calf affected, we have to consider that we might be dealing with a more ‘global’ problem, meaning that we could be looking at condition that can spread to others in the herd. That said, if we only have two affected and no further cases, then it is possible that we have a fluke of two calves with non-transferable conditions like spinal trauma, and spinal cord abscess. Both of these can appear as a sudden or progressive type paralysis of the back legs with no other clinical signs of illness. I would keep these in mind, but rule out our other differentials first. The more global issues we have to consider will be those of infectious (viral, bacterial, parasitic), nutrition, and toxic agents.

If we started with one leg affected, we need to know what the was causing the initial lameness. You have mentioned there was swelling on the lower leg of the second calf, but you didn't mention if it appeared to be associated with the joint or not.

If it was a swollen joint, suggesting a bacterial induced joint ill, we can see these animals become septic and see spread of the bacteria into other sites.

But if we are looking at tissue swelling and there was trauma to the skin, we have to consider one of the Clostridia at work. This can include Blackleg, Tetanus and Botulism. And since there is no history of vaccination (of calves or mums), they would be naiive to these bacterial agents.

Had there been no direct changes to the leg itself, then this can be a hint that our problems are spinal, brain, or induced by metabolic issues (this is where toxins, nutritional deficiencies and systemic imbalances come in).

First considering our infectious agents, we do have to consider the Clostrdias. As well, tick borne disease/paralysis, E.coli mengioencephalitis (where brain bacterial infection causes these disease), and Listeria (though I'd have expected circling with this one).

Looking into our dietary causes for progressive weakness and down calves, we do have to consider the imbalance of electrolytes. These include hypocalcemia, hypomagnesemia, and hypoglycemia, ketosis, and dietary deficiencies such as copper, vitamin A, vitamin E, selenium, thiamine, potassium, and phosphorus, as all of these can present as neurologic disease of this nature. So, it would be prudent to review their diet (and whether your pasture soil is low in something like selenium, magnesium, etc.) and consider supplementing these calves and monitor for treatment response.

Of course, we must also consider toxins, like ingestion of poisonous plants. As we have already discussed paddy melons are toxic to ruminants and should be removed the field (or the cattle should be moved to another field). That said, it is less likely these are to blame for these two calves’ issues. Rather I would be more concerned of plants like Rye grass, Bermuda grass, Pigweed, Pokeweed, Milkweed, Rough bearded grass, Bracken and Ragwort, etc.). We also have to consider that plants with high nitrate levels can induce this type of condition. As well, non-plant based toxins can also cause issue and some we’d have to rule out is exposure to zinc, mercury and arsenic.

There are also number of parasites that can cause issues of this nature, and if they are not wormed they may be at risk. Sarcocystis and Coenurosis would be considerations.

Overall, I would first advise having a another close look at these calves. Check their joints for swelling or heat (which will point to local bacterial disease of the joints). Also check whether they still have motor control (and can move their legs) or sensation in the legs (since this will point us to spinal based disease).If you have done that since we start speaking, then you will already have a good idea of these. As well, I would advise double checking the diet for deficiency issues to be sure. Consider supplementing some of those more common causes of downer calves. As well, make sure there isn’t something toxic he could have picked up in the external environment.

If you are struggling, consider getting your vet involved so they can help narrow down this list further. Since they haven't been vaccinated and one did have a swelling, it would be prudent to have the vet out in this case. Specifically, because if you are dealing with a Clostridia disease, you will need antitoxin as well as antibiotics and you would need to consider a vaccination regime for the other cattle (so its worth making sure this can be ruled out in these calves).

Depending on their findings, the vet will help you address potential clostridial outbreak. As well, if another bacterial agent is to blame, they can provide the appropriate antibiotic therapy. As well, it might be a case of treating against ticks if this is an issue in your area (as well a checking the calves for active tick infestation).

Overall, it is going to be a case of ruling out the above as much as possible and supportive care. That said, if there are any further animals affected, it would be worth considering submitting one of these down calves for post mortem. The pathologists will be able to evaluate the internal changes from the causative agent, culture potential bacterial causes so that drug sensitivity can be discovered, and will be able to test the mineral levels in the tissue to give you an idea if any of these are behind the signs.

I hope this information is helpful.

Please let me know if you have any further questions.
If you have no further questions, I would be grateful if you would press the wee green accept.
Thank you,

Dr. B