As political pressure intensifies and focuses some uncomfortable attention on how cattle feeders use antibiotics, researchers have been engaged in a constant quest to find some useful alternatives to them, alternatives that can not only keep the politicians happy but also still work as well as antibiotics do. In that spirit, British Columbia researchers will report in an upcoming issue of the journal Research in Veterinary Science on the practical—and apparently successful—use of nitric oxide at receiving to help protect calves against Bovine Respiratory Disease Complex, or BRDC.

Naturally produced by the body (and not to be confused with the nitrous oxide gas you used in your gearhead days), nitric oxide serves the primary function of permitting the cells of the body to communicate chemically, facilitating many of its physiological processes. For instance, a dose of it can quickly and powerfully cause the circulatory system to dilate, opening up otherwise restricted blood flow; that’s why doctors give some newborn babies with poor lung function a dose of nitric oxide gas or give heart attack victims nitroglycerine or amyl nitrate--nitric oxide is the functional molecule those drugs release once they’re ingested.

But in addition to those physiological functions, the British Columbia researchers note, scientists also know nitric oxide has some antimicrobial properties against not only bacteria, but also yeast, fungi and viruses, both in the lab and in the animal. It also provides cell-signaling functions that can encourage the growth and function of immune cells to naturally protect the body from those pathogens. When other Canadian research from 2006 gave it over a period of three days by nasal tube to calves they had purposely infected with BRDC, they found it proved an effective treatment.

The problem with that earlier study was the necessary delivery device was a bulky and cumbersome patchwork of multiple gas tanks, regulators, heaters and humidifiers inherent in gas delivery, in addition to requiring 20 minutes daily to treat each calf. This latest study eliminated that problem by creating a simple nitric oxide spray that could be shot into the nose much like a nasal vaccine in under 5 seconds. The British Columbia team tested the safety and effectiveness of that spray for its potential to prevent BRDC in crossbred, multiple-sourced, commingled commercial feeder calves when given at arrival processing. Rather than purposely infect the calves as the 2006 study did, this one actually bought the 85 calves through a conventional auction system, shipped them for four to six hours, put them in a typical commercial feedlot—with the exception of providing them an under-roof area with straw bedding—and processed and fed them as most commercial feeders would. By re-creating the real world of feeder calf procurement and handling, they hoped to achieve a typical BRDC incidence rate of between 30 percent and 60 percent in the experimental calves.

As the animals were run through the chute during normal receiving processing, the research team gave them either a shot of the nitric oxide nasal spray or a placebo shot of saline into each nostril. The application took less than 5 seconds on average per calf to administer.

All the calves were then assessed regularly for BRDC by trained pen riders who had no idea of whether the calves they were checking had or had not been treated with the nitric oxide. Those personnel assessed the calves based on the appearance of respiratory signs, digestive signs, body temperature and lethargy. Animals determined to be suffering BRDC were pulled, treated and re-treated as necessary.

And the results? After throwing out the data for animals determined to have already been suffering from BRDC at arrival, the results on the remaining 40 control and 42 treated animals showed:

  • For the first two weeks after arrival, the number of nitric-oxide treated calves that needed pull-and-treat for BRDC was almost three times less than those from the control group—five vs. 13, respectively.
  • In the first seven days after arrival, the control group was suffering a 17.5 percent BRDC incidence rate vs. the nitric-oxide treated group’s 2.4 percent. In other words, of the eight out of 82 calves pulled for BRDC in that first week, seven came from the group that received only saline; only one came from the group given nitric oxide.
  • For those animals that did get sick after arrival, the most common day on which they were pulled as sick was day 8 for the saline-only calves vs. day 18 for those given nitric oxide.

Affect of nitric oxide on BRDC incidence

The study authors point out their results on BRDC incidence are similar to those reported in clinical trials using antibiotics metaphylactically, although they also point out in fairness there’s no evidence to believe nitric oxide would perform as well as antibiotics when it comes to BRDC deathloss, weight gain or meat quality. More research is needed in those areas. However, they theorize nitric oxide could bring its own additional benefits over metaphylactic antibiotics, including:

  • While antibiotics are specific to bacteria—often particular bacteria--nitric oxide seems to be effective against not only a wide spectrum of bacteria, but also viruses. So nitric oxide could bring feeders the added benefit of lowering the viral load which we know contributes to the BRD complex in feeder calves.
  • Because nitric oxide is a broad and non-specific antimicrobial that works through multiple biochemical targets in the body, it’s probably less likely to encourage populations of bacteria to develop resistance, as antibiotics are believed to do.