Data show that we are not winning the battle of cattle respiratory diseases, and there may be a number of factors leading to that.

Brett Terhaar, beef cattle technical consultant for Elanco Animal Health, shared a chart showing a steady climb in heifer and steer mortality from 1997 to 2021. “A lot of things have changed over the years,” he said in a webinar sponsored by Elanco Animal Health the last week of September. “Genetics is certainly one of the things that is very different. Twenty-five years ago, you’d see a 700-pound steer that we would call a yearling. Now it’s, not uncommon to see a 700-pound steer be 7 months old.”

Finished cattle are also being fed to larger sizes, where 20 years ago “finished cattle may have weighed 1,150 pounds — and by 2010, the finished steer may weigh 1,300 — and now, certainly in the Midwest, I am seeing steers leaving the feedyard at 1,600 pounds, and that may be the pen average,” Terhaar said. “The body size of these animals coming into the yard and leaving is greatly increased.”

Even though the physical size of these animals has changed over the years, a calf’s lung capacity has remained at about 12 liters, as compared to a horse that has a 40-liter lung capacity. “So their lungs are relatively small to their oxygen requirements,” he said.

While a variety of beef producers’ favorite antibiotics — Micotil, Nuflor, Baytril, Advocin, Excede and Draxxin — have been introduced over the years, Terhaar overlaid a chart over the aforementioned chart, showing the timetable of those antibiotic introductions. Regardless of antibiotic use, the mortality trendline continues upward.

“Management isn’t in a bottle,” Terhaar said.

Antibiotics still have a place in herd health management when necessary, but nothing trumps good old animal husbandry. That starts when bringing in new calves, ensuring a high-stress time is as low stress as possible.

“It seems a little boring, and there isn’t much to sell there or talk about, but the way we manage our cattle is really important,” he said.

Starting with husbandry and management, Terhaar outlined the steps to get the most out of calves this fall.

Health of the herd

Early in his veterinary career, John Groves focused on the individual calf when health issues arose. “As I grew as a practitioner and as the operations grew that I worked with, over time I viewed the ‘patient’ as the population; so instead of thinking about what happened in individual animals, I often thought about what happened in the population of animals,” he said in the Elanco webinar.

Groves has a private, exclusively beef practice in Eldon in central Missouri, where about 75% of his practice deals with feeder cattle and 11% cow-calf operations, and the balance as a consultant.

When switching from that single focus, Groves now looks at percentages. “Percentages of animals in a pen that required a second treatment or percentage of animals that died. So that’s quite a different perspective.”

As Terhaar suggested, Groves said herd health needs to start with animal husbandry, “which is the careful and meticulous and prudent management” of our animals. However, he acknowledged the introduction of vaccines and antibiotics have allowed cattle producers to stray from the principles of animal husbandry.

Though usually thought of as a way to prevent foreign animal diseases or disease eradication, Groves said cattle producers need to take a close look at biosecurity and biocontainment to control how microbes spread throughout populations.

Herd health simulation

Realizing that his clientele are visual learners, Groves uses a computer-based herd health simulation “as a new way to look at disease dynamics.” His simulation looks at a group of calves that is either immunologically naive or immune calves; calves infected with an infectious microbe; and calves that have recovered.

“We model the bad-luck probability, the randomness that is in systems,” he said. “I will run my model multiple times — it will always come out different because helping cattle is not well defined, it is not deterministic. It’s what we call stochastic, which means there are various just luck and randomness [situations] involved.”

In these simulations, Groves controls the random probabilities, and plugs in a 5% probability that a calf is infected when it enters the herd. In a lot of 100 calves, that means five are infected. Through the modeling, those five infected calves “will randomly walk around and bump into other calves and, based on the probability equations, infect them.”

As his simulation proceeds through Day 7, 14, 21, 28, 35, 42 and 49, one sees how disease works its way through a pen or herd. He usually stops the simulation at Day 42 or 49 to coincide with the industry’s 45-day weaning. “If you can get 45 days weaned, you’re solid … we like to point it out that disease will almost always have stopped spreading on Day 45 in well-vaccinated farm calves.” He added that the 45-day rule is abandoned in naive populations, as disease stops spreading closer to 70 or 80 days on feed.

Use of actual client production records

While controlling the randomness in the simulations, Groves plugs in actual production records from his clients to build the models, so producers can see a scenario built on their operation.

Groves stresses the importance of calf health management, especially with high-risk cattle. “Disease dynamic as it relates to days on feed is a powerful point of leverage in people that handle naive cattle, and we can develop these tactics [based] on how long it takes to populate a pen and where you pen the cattle,” he said.

Through his simulations, Groves showed the effectiveness of where and how to pen calves if they do not arrive all on the same day, and he encouraged producers to create a map of their facility to think “about how can I use time and space to separate cattle by days on feed. You can really lower the rate at which these epidemics occur in your yard.”