The cow at the edge of Tony Louters’s dairy farm in Merced, Calif., held 11 gallons of milk and a secret: In the next 48 hours, she would become sick.

On many farms, the health signs would have gone undetected, costing hundreds of dollars in lost milk. But thanks to a high-tech collar that each of Mr. Louters’s 700 cows wears around its neck — fitted with movement sensors and Wi-Fi — he learned the cow’s diagnosis at 5:30 a.m. when his computer pinged with an alert about its biometric data.

By 6 a.m., Mr. Louters had given the cow a remedy of probiotics and warm water that solved the problem before it began.

“It’s the closest we can get to talking to the cows,” he said.

Mr. Louters, 52, has used the collars since they debuted in 2013, back when the devices were no more advanced than a pedometer. But in recent years, Merck, the health care company that makes the collars, has added new kinds of sensors and software to the wearables and artificial intelligence to help process the data.

The devices are part of an industry known as precision farming, a data-driven approach for optimizing production that is booming with the addition of A.I. and other technologies. Last year, the livestock-monitoring industry alone was valued at more than $5 billion, according to Grand View Research, a market research firm.