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Determine the risk level of feeder calves

Animal Health: Knowledge of how weaning was handled is useful information

There are many factors to consider when bringing in calves to feed to minimize BRD (bovine respiratory disease). It is still the number one cause of morbidity and often mortality in our feedlots.

Knowing the history of the calves at weaning time, distance transported, vaccination and health history, as well as upcoming weather conditions will help you determine level of risk.

Independently each pen or group of calves needs a risk category ranging from low risk to ultra-high risk in order to determine how they should be handled. The overall goal is to prevent a disease outbreak and high death loss by implementing management changes to get top performance from your calves. If we can determine risk level ahead of time that gives us a head start in battling the respiratory and other pathogens we know the calves may be exposed to. The final step is making the economic calculation of preventative cost in terms of vaccines, labour, or metaphylactic antibiotics versus treatment and potentially higher death loss. As with most things in farming this is a gamble and of course there are always unknowns that can blindside us.

Handling procedures

In bringing in calves, or for that matter feeding your own calves, there have been many factors which increase risk and we need to manage or handle these as best as we can. Try and ask yourself the question ahead of time. What is the risk level of this group of calves to developing respiratory disease and are there any management changes I need to do to mitigate or minimize this risk.

High-risk calves for developing BRD are generally considered those presenting with one or more of these points.

  1. They have been commingled because they were sourced from an auction market or mixed at home. Once a group has settled avoid adding in more calves. The quicker a pen is filled with animals sourced from a minimal number of original owners the better.
  2. Extended transport times where calves become stressed and dehydrated. Loading and unloading are more where the stresses come in but if there are huge distances during transport, such as bringing in cattle from one or more provinces away, in my opinion tips these calves to ultra-high risk. The more locally we can derive cattle the better. That ‘s not always possible since where calves are raised and fed can be two totally different areas of the country. Think about using electrolyte solutions such as ”destress” before transporting long distances.
  3. Bad weather or wide temperature swings can create severe stress. Watching the weather channel may help but you need to buy when you can. The farther the distance travelled the more likely these temperature fluctuations are going to happen.
  4. The on-arrival procedures such as castration, dehorning and branding all have their stressors. The cattle industry is always under scrutiny from an animal welfare perspective for these procedures. In most cases castration is done way ahead of weaning. Polled bulls are eliminating horns or the calves are dehorned early. Dehorning in the feedlot these days generally involves tipping the few horns that are left. If financial institutions and feeder associations or grazing reserves did not require branding there would be little of that done anymore. If you need to brand minimize size and number of characters as much as possible. Better analgesics (pain killers) and anti-inflammatory drugs are being commonly administered that will help minimize stress in these painful situations.
  5. Calves recently weaned with no or a poor (unknown) vaccination history. The old preconditioned programs where calves have already been weaned a month is ideal. The greater pressure we have from respiratory pathogens, the more important the protection measures. This includes the viral as well as the bacterial components of the BRD complex. Don’t forget the clostridials and histophilus in your vaccination protocols.
  6. Lightweight calves or nutritionally compromised or parasitized (internal parasites that suppress the immune system) may also carry an additional level or risk with them. To me calves under 400 pounds would be considered ultra-high risk. The 400- to 500-pound weight calves are high risk. And with 600-pound or heavier calves the risk levels depends on the other categories mentioned earlier. Veterinarians will vary in their opinions here.

Determine risk levels

If calves fall into any one of the above categories they are considered high risk. Low risk is essentially your own preimmunized calves, weaned at home in a situation where they know where their feed and water is. Weaning older, heavier calves and weaning in good weather with either fence line or some other type of soft weaning is considered low risk. It is ideal to remove the cows from the calves that have access to a ration they are familiar with. Even in these situations pulls for respiratory disease can climb and you reach a point where treating them with antibiotics may become necessary to thwart an outbreak.

With high-risk calves, the question is what to do with them when they are received at the feedyard.

Your herd veterinarian will have a protocol for what they believe best. Again it may vary pen to pen. Most would consider giving the necessary vaccinations and processing and covering with metaphylactic antibiotics. The newer macrolide antibiotics last a long time in the lungs and they are a completely different family to our treatment antibiotics. Usually the label will state they are for the control of BRD or to use in cattle at high risk of developing BRD. This is where knowing the risk level of the calves coming into your feeding pen is critical in deciding which ones to treat. In the past antibiotics were given in the feed but they needed to be given for a long period and are hard to manage in large feedlots in order to avoid residues.

Treating with macrolide antibiotics come with a cost and require labour so this is where the risk benefit has to be considered in the equation as well. Our experience has shown that with feedlot veterinarians assessing the pens and using the appropriate vaccination, deworming and metaphylactic treatment protocols, BRD levels can be drastically reduced. In the future other antimicrobial treatments as well as earlier detection of BRD and even more comprehensive vaccine programs will hopefully reduce mortality and morbidity even further.

About the author

Columnist

Roy Lewis is an Alberta-based veterinarian specializing in large-animal practice. He is also a part-time technical services vet for Merck Animal Health.

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