Animal Health Matters: Should calves get vaccinated on feed yard arrival?
A necessary – but entirely unpredictable – feature of being a veterinarian in a small town were the middle-of-the-night calls: Calvings, horse colics, sick dogs. Strangely enough, however, I’d occasionally have some scheduled middle-of-the-night calls, when area farmers would buy calves to feed in the fall. These calves were put together from salebarns, loaded onto trucks, and hauled over to the feedlots on their farms.
Many of these operations lacked facilities in which to process (vaccinate, implant, pour) those calves. Our clinic’s location along the interstate proved valuable in those cases. The trucks could easily pull off, unload the calves, have us work them, load them right back up and haul them to their new home.
The usual scenario had these calves being loaded after a late sale far away, to arrive at the clinic in the early morning hours. Whichever vet drew the short straw would get out of bed, open up the clinic, gather the equipment, efficiently vaccinate the potload of calves, and get them on their way.
Turns out that was a dumb thing to do.
My thought process zeroed in on preventing shipping fever — Bovine Respiratory Disease Complex (BRDC). The bane of cattle feeders everywhere, BRDC would often show up a week or two after calves entered the feedyard, causing sick calves with breathing problems.
The primary tools at our disposal for BRDC prevention are vaccines. Given to calves ahead of expected illness, they aim to protect calves against the effects of respiratory viruses like IBR and BRSV, and bacteria such as mannheimia and histophilus.
As a vet watching these calves trail down the ramp into my clinic in the middle of the night, I knew that the shipping fever clock was already ticking. Some of those calves were already harboring BRDC germs and just weren’t sick yet. I also knew that vaccines take a couple weeks to achieve their main effect. So I wanted to get those shots into the calves as quickly as possible.
Despite vaccinating these calves before they even hit the feedyard, it didn’t always work. It wasn’t uncommon to visit these same calves weeks later to treat the sick ones or post the dead ones. These failures would get chalked up to bad weather or bad luck.
Research into vaccinating highly-stressed calves at feedyard arrival with BRDC vaccines is now helping us explain why my late-night processing sessions weren’t always successful. These calves fit the definition of stressed: loaded (sometimes weaned) onto the trailer, co-mingled at auction markets, trucked long distances, unloaded at a strange vet clinic, poked with needles, loaded up again, and trucked to an unfamiliar new farm. Longer-acting stresses like this affect the calf’s immune system, weakening its defenses against BRDC germs, as well as its response to vaccines.
Recent research shows that vaccinating calves like this on feed yard arrival doesn’t improve calf health or performance. Immune responses to killed vaccines are impaired, and the germs in modified live vaccines tend to grow more unchecked in stressed calves, raising the possibility that they could create problems instead of prevent them.
If vaccine on arrival is ineffective, what’s a person to do? The key to keeping any calf healthy is priming their immune system well before they need the protection. This means that the best use of BRDC vaccines happens on the cow-calf operation, prior to weaning. Calves treated in such a way have lower BRDC rates once they hit the feedyard.
What if those calves haven’t been vaccinated in that manner? Certainly, it’s a conversation to have with a veterinarian, but to me it starts with understanding the chronic stresses experienced by such calves, and the limitations of effectively vaccinating these calves during that stress. In many cases, delaying vaccination until after calves are over their stress will pay higher immune-system dividends than further stressing them by running them through a chute to give them a vaccine that may not work in the first place.
There’s more research to be done, and questions to answer, about how to best provide for the health of calves entering the feedyard. But in my mind, more and more of it points to the understanding that how we manage the young calf’s stress is more important than vaccinating them at an inopportune time.