Big Apple veterinarians are being forced to put human lives above animal lives for the first time in their careers — as besieged hospitals desperate for ventilators continue a losing battle against the coronavirus.

Mayor Bill de Blasio urged veterinarians Tuesday to lend their human-grade ventilators to infirmaries, but vets at big animal hospitals across the city have already been in the process of rounding up supplies for the last week, the chief medical officer at Veterinary Emergency & Referral Group, Brett Levitzke, told The Post.

“As veterinarians, we take an oath to relieve suffering in pets and that’s what our careers are centered around. I think this is the one time, in a crisis like this, where the needs of a human life would supersede [a pet’s life],” Levitzke said.

“There’s usually a distinct line between veterinary medicine and human medicine and there’s no crossover. That’s what makes the time we’re in so unprecedented. We are in such a desperate time that we’re having this crossover of using machinery and equipment on the veterinary side for the human side.”

VERG, one of the city’s largest 24-hour emergency animal hospitals, is one of the few specialty centers that have a human-grade ventilator they use on animals.

“If a dog or cat is hit by a car and they have tremendous contusions in the lung, if they have horrible heart failure or horrible pneumonia due to an infection, we put them on the mechanical ventilation to get them through until their lungs can heal,” Levitzke explained.

“They’re only found in specialty hospitals and there’s a couple of other specialty hospitals throughout Brooklyn, Queens and Manhattan and maybe between all of them, we had maybe a dozen or so and I know they’re all being spoken for.”

Last week, Blue Pearl Veterinary Partners donated seven of their ventilators to New York-Presbyterian Hospital in Manhattan, a spokesperson told The Post.

VERG only has one ventilator — and the decision to forgo their ability to do ventilation is one they “don’t make lightly.”

“It’s heartbreaking,” the animal doc admitted.

Without it, Levitzke’s team will have to resort to “manual ventilation” — a labor-intensive process that requires a veterinary technician to manually squeeze a bag of oxygen into an animal’s lungs every 10 to 20 seconds.

“When you do it manually, it’s not as accurate … the prognosis probably wouldn’t be as good. The pets that need to go on ventilators already have a pretty guarded prognosis. It does make it a little bit trickier,” Levitzke explained.

“We had a cat just come in [Tuesday] that was in horrible heart failure and would potentially need to be on a ventilator. Unfortunately, the owners elected to euthanize the cat,” he said.

If they hadn’t, the cat would’ve been set up on the ventilator, but “if and when” VERG got the call that their equipment was needed, the feline would’ve been switched over to manual ventilation.

Still, “it’s just the right thing to do,” Levitzke said.

“If the option is to have the ventilator here for potential use, or getting it out on the front lines where it’ll definitely be used, it’s not even a question. We obviously want it out on front lines.”

He said the hospital has been in touch with the New York State Department of Health and if he doesn’t receive instructions soon on where to bring the ventilator, he’s planning to go “door to door” until a hospital takes it.

“We all have to do our part,” Levitzke said.

“And if we as veterinarians can contribute in some way to help our human counterparts, then we certainly will.”