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Preconditioning calves primes their health through all stages of production

by Wyoming Livestock Roundup

“A calf that is vaccinated on the ranch and weaned on the trailer is not a preconditioned calf,” states Kansas State University Beef Cattle Institute Director of Outreach Dave Rethorst.

“I like to define preconditioning as calves that are vaccinated, weaned on the ranch, fed on the ranch for 45 days and then marketed,” he adds.

After 45 days, the calves have completed weaning, been started on feed and are ready to be moved to the feed yard or other operations.

Preconditioning process

“We are preparing these calves for the next stage of their lives and trying to keep them alive without wasting resources,” Rethorst notes.

A preconditioned calf is familiar with a feed bunk and a water tank, and they have been immunized, dewormed, castrated and dehorned.

“The difference is in the pounds,” he comments, noting that preconditioned calves may cost more, but their value will also be higher.

Nearly 750,000 cow/calf producers in the U.S. funnel their calves into a few thousand feedlots, which funnel into only a small number of packers.

“We want to develop the immune system of these animals, so they can go through all of these phases,” Rethorst continues.

Early impacts

Developing the immune system begins early in life, says Rethorst, who mentions that impacts occur even before birth through a process called fetal programming.

He became interested in fetal programming at a veterinary consultants’ meeting at the University of Nebraska, when he heard about a study involving protein in a cow’s diet during her last trimester of gestation.


“Steer calves out of supplemented cows performed better in the feed yard, and heifers out of supplemented cows performed better reproductively,” Rethorst explains.

His own studies involve trace minerals.

“If we were going to cheat cows on trace minerals, it was during mid- to late gestation,” he comments, adding that is the worst possible time to do so.

Shorting the cow on nutrients at that time robs the developing fetus of minerals essential to its development.

“That last third of gestation is when the cow is dumping trace minerals to the calf and priming its immune system,” he says.

The immune system of the fetus begins to work around 120 days or at about four months of gestation.

“It makes sense that we should be fortifying the cow’s diet so that when the calf hits the ground, it is able to fight off E. coli, Salmonella, Crypto and other causes of scours,” he explains.

Research at the University of Wyoming is beginning to show that an energy deficiency late in gestation leads to smaller organs, such as the brain and pancreas.

“Focusing on fetal programing is important, whether it’s protein, macro or micro minerals,” he states.

Castrating and dehorning

After the calf is born, it should be dehorned and castrated as young as possible, according to Rethorst.

“If we’re handling them at birth, and mom isn’t snorting in our pocket, let’s take care of castration when we put the ear tag in,” he suggests.

He adds that it should at least be done within the first few months to reduce stress on the animal.

“If we are using breeds that have a polled option available, let’s take the horns off when we turn the bull out,” he says.

Otherwise, dehorning should be done while the animals are still babies, with burning or paste.

“Deworming is another thing that we can do to get one step closer to an immune system that works right,” he adds.

Preventing exposure to pathogens will help the calves stay healthy.


“When it comes to vaccine, it’s all about timing and building,” Rethorst continues.

He recommends working with a veterinarian to develop the right combination.

“On spring calving cows, we want to start vaccinating these calves this spring,” he says.

Rethorst believes that preconditioning calves helps insure they are strong and healthy throughout the next stages of production.

“We are talking about preparing calves for transfer from one segment of the industry to another,” he explains.

Natasha Wheeler is editor of the Wyoming Livestock Roundup and can be contacted at

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