A lot happens to a calf from the time it leaves its dam to when its hooves hit the feedlot. Every step of the way is a chance for viral or bacterial exposures that cost buyers in time, expense and lost gains.
West Texas A&M University's John Richeson reported on a study comparing treatments of high-risk calves from ranches in the area during Boehringer Ingelheim's recent "Business of Beef: Health and Management Summit."
The focus of the study was bovine respiratory disease (BRD), which Richeson called a decades-old challenge, influenced by an antiquated marketing system and more recently an industry-wide focus on genetic selection for rapid growth as opposed to disease resistance. Anytime calves are transported, he noted, the biggest disease concern is BRD. Today, there is minimal incentive for small operations to precondition calves, compounding problems for feeders.
Richeson noted that, while cow-calf operations are coast to coast, the feeding industry is more geographically concentrated, creating the necessity of moving and commingling calves, often over long distances. The journey many calves take from home to feedlot can be incredibly stressful. Richeson said it is not uncommon to see a calf separated from its dam on a Tuesday morning, go through the auction market, be commingled, go to an order buyer facility, be commingled again, spend a night being shipped, and finally arrive at the feedlot on a Friday. Within 14 days, BRD outbreaks will often be seen under these conditions, due to the chronic stress these calves endured and a lack of preconditioning early in their lives.
The study looked at 479 bull and steer calves from auction markets in central and east Texas, during a 56-day receiving period. It compared metaphylaxis with tulathromycin (META) and a modified live virus respiratory vaccine (MLV). The goal was to evaluate how the treatments influenced health and growth. At its most basic, the study found health and performance of high-risk feedlot cattle was improved by the META treatment, but not by administration of the MLV at the feedlot on arrival.
The study noted while about 96% of newly arrived cattle are administered a MLV vaccine containing viral antigens commonly isolated from BRD-affected cattle, the efficacy is not well supported. Waiting to administer the MLV vaccine at 14 to 30 days post arrival, however, did result in improved outcomes.
"If they came in with preconditioning titers, they had much greater resistance to BRD than the [high-risk] auction-market animals," added Richeson. "Feedlots recognize the value of preconditioning; there aren't enough of these calves to meet the demand. It's a challenge because a lot of small cow-calf producers are spread coast to coast, and if they don't all manage their cow herds in similar ways -- for example, with controlled breeding -- calves are spread out and it's hard to implement a preconditioning program."
Metaphylaxis remains a highly effective treatment for high-risk calves, but Richeson questioned how sustainable this is due to antimicrobial resistance and food-safety concerns. In addition, he pointed to animal welfare concerns over high-risk calves.
"As metaphylaxis use becomes more scrutinized, the value of the high-risk calf will decline," he said. So, while the study showed significant advantages in performance for cattle that received the META treatment, including in the amount of grain they consumed, this is not a long-term solution.
"With high-risk calves, one of the biggest challenges is to see them get up to feed quickly. When they get here, they are in a negative energy balance, and the sooner we can correct that, the better," he explained.
THE EAR TAG TELL
Richeson said one thing they looked at in the study was whether a calf came in with a ranch ear tag. They found those with tags tended to be significantly better in terms of health and performance.
"That tells me that, if they have a tag in their ear, they've been handled at least once, and probably there is a higher likelihood they've been vaccinated, were on better nutrition and a mineral program. It's a proxy that shows some previous health management," he noted.
Ultimately, some may wonder why feeders would care about preconditioning if there is an effective treatment to turn around high-risk calves. Richeson said it's important cow-calf producers know the feedlot industry is moving away from a population-based treatment protocol to one much more targeted in which calves are assessed and treated with metaphylaxis on an individual basis.
"We have always managed the population, but moving ahead, we have to manage the individual animal better. This means only those animals that really need and will benefit from treatment will receive it. There is concern about resistance, and we have to target treatment to preserve what we have."
In addition, Richeson noted the industry is more scrutinized today regarding antimicrobial resistance and animal welfare. That means the value of high-risk calves will continue to decline.
TWO KINDS OF STRESS
When it comes to cattle, Richeson added, there's acute stress and there is chronic stress. Understanding the
difference explains why it's better to vaccinate calves as part of a preconditioning program on the ranch than to try to catch them up once they hit the feedlot.
"Acute stress is minimal and short term, and it is immuno-priming, meaning it makes the immune system more ready to act," he said. "Chronic stress is when there are lots of different stressors added together over a longer time, and that causes immuno-suppression. In the context of the beef business, branding would be an acute stress, but that long process from dam to the feedlot is a chronic stress. Calves tend to be immuno-suppressed when they arrive at a feedlot."
This suppressed immune system creates a perfect storm to support BRD, which Richeson said is probably the most complicated mammalian disease on the face of the earth.
Richeson added they've found the most important aspect of preconditioning is keeping a calf on the ranch 45 days or more. Next in importance is early castration and deworming, followed by getting calves bunk broke and on a good nutritional program. Vaccinations and deworming round out the program that puts calves in the best position to weather the transitions from ranch to feedlot.
The vaccination aspect, added Richeson, is not very effective once calves reach the feedlot and are stressed. In fact, it may do more harm than good at that point. The report noted the timing of MLV administration relative to the natural viral challenge and stress-induced immuno-suppression is questionable due to increased antigenicity of the vaccine, natural virus exposure and timing of BRD outbreak relative to immunization.
Victoria Myers can be reached at firstname.lastname@example.org
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