Bovine Respiratory Disease Complex Flashcards
What two things are necessary for treatment success when using antibiotics?
Proper antibiotic use as well as the calves defenses
-drugs alone wont do the job
Prior to 1992, what was used to treat infections in stocker cattle?
Not a lot was available besides oxytet and sulfas
-no single dose treatments were available
-there was a ton of extralabel drug use
What was the golden era of antibiotic use in stocker operations?
Started with the introduction of Micotil in 1992 (first highly effective therapy against BRDC)
What is the current era of antimicrobial use for BRDC
Due to a rise in vitro resistance clinically used antibiotics appear to be less effective than they were previously causing mortality in feedyards to increase
What are the 3 causes of apparent treatment failure?
Problem with the timely recognition of disease, antibiotic resistance, or the presence of superbugs
What are some of the reasons that timely disease recognition may be difficult for BRDC?
-It often is difficult to diagnose until its too late and farmers aren’t as observant as they think
-often cases arent caught until the calves are open mouth breathing
What is the pathogenesis of mannheimia hemolytica infections?
- immune cells in the lung move to attack mannheimia
- White blood cell engulfs the bacteria
- White blood cell implodes killing it and the bacteria
- Mannheimia produces leukotoxin that attacks the WBC before it attacks the bacteria
- When WBC die they release the substances they used to kill the bacteria resulting in severe lung damage
Define metaphylaxis
Mass medication of cattle with antibiotics in populations at very high risks of outbreaks
If you have treated a herd metaphylactically, how should you change your protocol when treating a sick animal?
Use an antibiotic in a different class
When should you treat cattle metaphylactically?
If on arrival there is a greater than 35% chance of the calves getting sick, they are very high value calves. Can use as a substitute for time/labor of treating the sick calves
In the middle of an outbreak can use if the treatment failure is not related to antibiotic resistance, 25% of the calves were treated in one day, or 10% of the calves were treated for 3 days in a row
What does mycoplasma cause?
Pneumonia which is just as deadly as manheimia, joint problems resulting in severe lameness, and ear infections
Describe the signs of BRDC caused by mycoplasma?
Poor responsiveness to therapy, relapses from 1 week to 1 month later, hacking cough, mild signs follows shortly by severe labored breathing, clear nasal discharge, low temps compared to other causes of BRDC
Describe the lameness caused by mycoplasma
Severe swelling/lameness in one or more joints
-lameness is severe enough to cause calf to starve to death if not put in small lot with easy access to feed and water
-most calves will recover if given enough time (weeks to months)
How do you treat mycoplasma joint problems?
Antibiotics of little use, NSAIDs have little clinical effect, but opening abscesses may help (be careful not to enter joint capsule)
What is the best treatment for H Somni infections
Prevention with 1 gm CTC per 100 lbs of bodyweight
-not approved
What is recommended for when you should give up on treatment in BRDC cases?
After 3 treatments the chance of recovery is poor
How long should you wait before switching the antibiotic used?
Wait at least 48 hours to see if first line of treatment is effective before changing the regimen
What are two other lay term names for BRDC?
Pneumonia and shipping fever
T/F: Feedlot producers over time are shifting to be more okay with paying a premium to buy pre-vaccinated and processed animals
True
T/F: overtime feedlot mortality has trended downward
False, it has trended upward
T/F: Amount of money spent on antibiotics over time has significantly increased
True
What bacteria are included in BRDC?
Mannheimia haemolytica, pasterella multocida, histophilus somni
-less importantly bibersteinia trehalosi, mycoplasma bovis
Are most infections mixed or single organism?
Single
What is the most common pathogen responsible for BRDC?
Manheimia haemolytica
Can the agents responsible for BRDC be a part of the normal flora?
Yes, they are all part of the normal flora of the upper respiratory tract of many animals
Why is BRDC so economically important to feedlots?
It increases prevention costs, treatment costs, labor costs death losses, decreases performance, feed conversion, carcass value
What factors put cows at risk of BRDC?
Weaning, marketing, shipping, comingling, weather, nutrition changes, respiratory viruses
- sad reality is many of these changes happen very close together, making the transition to the feedlot the prime time for infection
How long is the incubation period for viral vs bacterial BRDC?
Viral: 3-5 days after exposure
Bacterial: 3-5 days behind the initial viral infection
Describe the pathogenesis of BRDC?
The viruses destroy the cells protecting the lung allowing for the bacteria to move from the URT to the lung
-the lung has little defense and lots of food so the bacteria thrive
Where does mannheimia live?
In the calf -part of normal flora
What are the main goals for stocker production?
To keep death loss between 1-4%, sickness <10-33%, and > 1.5 lbs ADG/calf
What is the most important factor in preventing BRDC?
Management
Describe the different categories of calves purchased from stocker yards?
Category 1: preconditioned (what you want)
Category 2: calves bought straight off of one farm
Category 3: fresh market calves
Category 4: stale calves (dont want these)
Define preconditioning
Calves have received all their core shots and they have been weaned for 45 days. They have been trained to eat and drink out of a trough
How does low stress handling and early weaning impact BRD mortality?
It decreases it as stress worsens the pathogenesis of the disease
What vaccines should pre-conditioned calves receive?
IBR-BVD Type I and II- PI3-BRSV (at least one dose should be MLV)
-mannheimia hemolytica (should contain leukotoxin)
-blackleg (7 way clostridial)
-all vaccinations should have occurred at least 2 weeks prior to shipping
What is the “double vaccinated” trend
To vaccinate all calves twice for all vaccines regardless of if the vaccine is labeled for a booster
- hasnt been shown clinically to be more effective
How can you rate preconditioned calves?
1: weaned calves, vaccinated and from one source or calves comingled prior to purchase
2. Weaned calves vaccinated from multiple sources
3. Unweaned calves, vaccinated from single source
4. Unweaned calves vaccinated from multiple sources
What should you do for category 1 calves after purchase?
Parasite control (deworm, delice, coccidiostat), +/- implant
What should you do for category 2 calves?
Should be vaccinated within 24 hours after arrival (5 way MLV and blackleg), plus parasite control (deworm, delice, coccidiostat), +/- implant
What should you do with category 3 calves?
First 24 hrs: Fresh clean water and excellent hay as soon as possible, vaccinate with 5 way and 7 way, parasite control, +/- pasteurella toxoid vaccine, selenium, grain diet, metaphylaxis
What should you do in the first 24 hours with category 4 calves?
Same as 3 plus metaphylaxis for sure
-should expect many of these guys to get sick and die
What is the best thing to feed calves right after arrival at feedlot?
Palatable feed, not too much starch (avoid grain overload)
How is a BVD PI animal produced?
-Over 90% is from a susceptible pregnant female infected with BVDV at 1-4 months gestation- calf is PI
-10% is when a PI animal becomes pregnant and produces another PI animal
What is the prevalence of BVD in beef herds?
4-10% of herds have at least 1 BVD PI animal and 0.25-0.5% of calves born are PI
T/F: The likelihood of buying a PI calf greatly increases with the more calves you buy
True
What test is available for BVD screening?
Ear notch- can run elisa (more common) or IHC
Why are samples commonly pooled for BVD testing?
To save money
Does the ELISA test differentiate between TI and PI?
NO- if positive, need to retest 3 weeks later. If still positive, cull
When should you castrate stocker calves?
Either much before shipping or much after (but the earlier the better as bull calves are more likely to get sick, gain less weight, and die)
