The Doctor Is In

by Dr. Allan Preston

Is it plagiarism if you copy your own material?

When working up this month’s column, I was reviewing a September 2006 piece on bovine respiratory disease (BRD) and by George, it was pretty good! Much of the information is quite applicable today, and much of it bears repeating.

So here goes with an October 2008 update on what has changed, what is new and different, what still is the same as it has been for years.

BRD is the biggest health threat in most feedlots, and adopting the wrong prevention and treatment strategies can have a very negative impact on the pen close out, and on your year-end financial picture. Make the right decisions and you’ll minimize the impact of the disease and maximize your economic return.
The incidence of BRD is actually increasing, despite the advances in antimicrobial therapy. Why?

There are several reasons including: the genetics of the cattle business, the selection of high performance cattle, the high concentrate rations we feed (often up to 90%), the concentration of feeding operations, the young age of calves entering the feedlot, the long number of days on feed and the shortage of qualified labour in the feeding industry.

The high morbidity and high mortality rates with BRD are only the tip of the iceberg. The hidden costs in reduced daily gains, more days on feed and reduced carcass quality at slaughter, all eat into the industry’s bottom line. And treating BRD can impose some significant labour and operating costs as well.

Since my days as a veet student, the goal remains the same – prevent BRD to whatever extent possible; diagnose and treat early; reduce mortalities and chronics; reduce relapses and labour costs; improve performance post-treatment; and improve the close out numbers for the pen.

BRD Defined
BRD is a disease complex that includes several bacterial causes: Mannheimia haemolytica, Pasteurella multocida, Histophilus somni; and the viruses IBR, BVD, PI3,BRSV; and the in-between “bug” Mycoplasma bovis.

There is a long list of risk factors that include: calves from multiple farms, calves in transit for long time periods, shrink due to lack of feed and water, weather variations (heat, cold, wet, dusty) and stress due to weaning, processing, castration and dehorning.

Unvaccinated calves, especially those coming from cow herds with a poor or non-existent vaccination program for BVD in particular, are an accident waiting for a place to happen - and it does once they are exposed to all of the above mentioned risk factors.

U.S. data supports what we see here in western Canada—the younger the calves are, the more they are co-mingled, and the farther they travel—the more BRD we see.

In the feedlot, BRD is defined as:
A fever of over 40C and a clinical aptitude score of 1 or 2; or
A fever of under 40C with a clinical aptitude score of 3 or 4.

What’s a clinical aptitude score (CAS) you ask? That is simply the signs of illness that the pen checker is looking for. These signs include everything from panting or head down, droopy ears, nasal discharge, gaunt appearance, weakness, staggery gait, refusal to drink and eat.

It is pretty hard to describe here and the secret of the successful pen checker is being able to identify the CAS 1 with the high fever. This is the calf that is just a little “off” but is in fact burning up. Catch and treat him early and the success rate goes way up.

The CAS 3 calf is barely able to walk, head down at his knees, and gaunt as the proverbial Greyhound. But his temp may only be 39C. This one is a lot harder to cure and much more likely to relapse. The CAS 4 calf is moribund – it’s too late.

Prevention/Treatment Principles
Here are five platitudes for BRD:
1. Be aware of the BRD risk factors and reduce that risk to the best of your ability.
2. Diagnose and treat early – and this may include metaphylactic treatment
3. Vaccinate for the common respiratory pathogens – and buy calves that have a good herd vaccination history.
4. Minimize contact between arriving and sick cattle. Separate processing and treatment facilities, receiving and hospital pen management.
5. Maximize nutrition for incoming calves. Make every mouthful count, these calves are energy deficient and need energy and protein quickly.

Now for some more specific treatment advice. The first and most important piece of advice is to work very closely with your veterinarian. One size does not fit all. What works for me doesn’t always work for you and what worked last year may not work this year. Each group of calves represents a unique scenario so you won’t be treating every pen and every truckload in the same way. Having said that, there are some overriding principles that I firmly believe in.

Sick calves need to receive a long acting antibiotic and be returned to their home pen right away. Being back in familiar surroundings with familiar pen mates and being fed the same ration, all go a long way towards a speedy recovery. Mark and identify the calf but leave him alone for a minimum of four or five days. Have a bit of faith in your treatment - give it time to work.

For those CAS 2 and 3 score calves, I believe that the success rate is improved by adding in some supportive treatment with a non-steroidal anti-inflammatory drug, maybe some B-complex vitamins, and even electrolytes for those that are really dehydrated. On the second pull (there will be some relapses) I go with an alternate long-acting antibiotic, then put them back in the pen again. If it comes down to a third pull, it may well be time for the hospital pen and a daily treatment regimen.

Treatment/Metaphlaxis Specifics
Now for the controversial part – drug choices. I repeat—these are my own professional opinions—you need to get the opinion and guidance from your vet for your feedlot.
As indicated earlier, every pen and every truckload is different. I don’t like to routinely medicate on arrival but prefer to medicate those loads that are at highest risk. For me, that means young, light weight calves; freshly weaned, co-mingled, shrunk and stressed calves that have been too long on a truck or in a sales yard.
Metaphylaxis is the mass treatment of a group of calves that are at high risk of breaking with BRD. It is a time proven management tool that reduces overall BRD morbidity and mortality.

A significant proportion of high risk calves will get sick early in the feeding period and it pays to curb disease before an outbreak occurs. The choice for drugs continues to evolve – Draxxin, Micotil, Tetradure, Nuflor and the many LA oxytetracycline brands.
I’ll leave it to you and your vet to make the decision, but remember, the guiding principles: one low dose, long duration of action, safe for man and beast, effective against the major bacterial causes of BRD, capable of reducing morbidity and mortality, reduced relapse rates, and, finally – cost.

Too often cost becomes the first and only factor – and the results can be disappointing. Also, too often the cost of the drug alone is considered, not the hidden costs of continuous monitoring, high pull rates, the labour and operating costs of “chute time.” Plus there may well be a false sense of security with the metaphylactic drug choice. Just because you treated the pen, a wreck can and will still happen, if the wrong drug was used on arrival. Using drugs in a mass medication program is serious business. The impact on animal health, on the bottom line for the pen, and on the bigger picture of antibiotic residues and resistance are all deciding factors. I’d rather use an expensive drug, do a better job, and have a clear conscious at the end of the day, than use the cheapest alternative and continue to have difficulty managing the BRD outbreak.

For straight forward treatment of pulls, the principles are the same. Again, it may be false economy to go with the lowest cost per treatment choice so use the product that will give you the best short term results, and the best pen close out results. Look at the treatment as an investment, not a cost.

Conclusion
Don’t ever forget the long list of causative and contributing factors to BRD. There are a lot of reasons why all cattle do not respond and do not live. Mycoplasma bovis and BVD are two known reasons for failure. Know when to call it a day, since some of the chronics are better off dead. Make sure the cowboys know that it is okay to admit defeat and humanely destroy these critters.

And don’t forget that prevention and management will minimize BRD, and maximize your treatment success when it does strike. Use those “magic bullets” to keep as many of those incoming calves alive as you can. Work with your veterinarian to sort out the complex issues around antimicrobial choices. The veterinary-client relationship is critical to your success.

Until next time . . .

- Allan Preston is a worn out former country vet, masquerading as a senior provincial bureaucrat dabbling in the cow-calf and feedlot business near Hamiota.