Is there any natural / local calcium supplement for cows?

Our two jerseys have now twice fallen badly ill because of calcium deficiency. They produce at least 20 liters per day when they're in good form. But the only source of veterinary materials is the govt department, and they always play hard to get with the calcium supplements, saying they're out of stock, will get some next week, etc. They always recommend that we just get them to come and give an injection regularly instead.

Do salt licks or mineral licks usually contain calcium and phosphorus? Is is true those are the main minerals that we should be concerned about? Our cows get lots of kitchen scraps including crushed eggshells, alfalfa hay, some wheat bran from a nearby mill, and limited fresh forage. People here often remark they look healthy. But then they get fits from calcium deficiency! I don't know much about cows, haven't been involved with them so much.

No seashells in this area. Some lime pits. Is it possible to dissolve lime in acid to neutralize it? Or not digestible, or not worth it?

We can order salt licks or supplements from other parts of India. For example, a zoo-vet friend of a friend recommended this:

HimCal
Calcium and phosphorus feed supplement
HimCal contains calcium and phosphorus derived from oyster shell. The ratio of Ca:P is 2:1. It ensures the formation of strong bones in growing animals.
Stimulates milk production: HimCal is fortified with galactopoetic herbs that stimulate the secretory functions of mammary alveoli and the promote growth of lobuloalveolar tissue, which improves milk production.
Key ingredients:
Calcium (Mouktika Sukti) strengthens bones in dogs and puppies.
Jivanti (Leptadenia reticulata) improves milk production, and maintains appetite and digestion in animals.

What do you suggest?

A salt lick is just that -- salt. NaCl and not much else. Even that Himalayan pink salt that is so trendy here in the States is just salt. And by the way, most salt that is mined from deep in the earth is pink, Himalayan is nothing special. Salt made by evaporating sea water and by scraping dry lake beds lacks these minor impurities and is white.

The HimCal sounds like a good supplement, you want to have the calcium to phosphorus ratio be 2:1 to assure proper absorption of both elements.

The more important question to ask is why aren't they absorbing the calcium in their feed? If you are feeding alfalfa and eggshells, those are both good sources of calcium, why do you still have a problem? Is there some underlying kidney disease or one of the many other causes of hypocalcemia? Maybe there is something in that "limited fresh forage" that is in the potentially toxic category that you should not be feeding them. There are many plants that are high in oxalates (rhubarb, dock, buckwheat), and when oxalate binds with calcium, that's what can cause kidney stones. While the body is trying to pass the kidney stones, its metabolism is saying "please, no more calcium, not until I get rid of these kidney stones, come back later", so it may not be absorbing the calcium it needs for other purposes on account of the stones.

One of the new trends in the states is free choice mineral, also called buffet or salad bar mineral. Instead of a mineral block that is a mix of salt and mineral in a multitude vitamin like delivery (set ratio based on average need), they deliver a dozen different individual minerals, including a couple sources of calcium and phosphorus.

My cows were short on phosphorus, not calcium. Just something to think about.

Also, what about dynamic accumulator plants? Do you have any that mine calcium and phosphorus?