NAVLE Bovine Herd Health 5 — Questions and Answers
Question 1: A herd of cattle in the Texas panhandle develops polioencephalomalacia (PEM). The most common cause in feedlot cattle on high-sulfur diets is deficiency or antagonism of which vitamin?
- Thiamine (Vitamin B1) (Correct answer)
- Vitamin A
- Vitamin E
- Niacin
Correct answer: Thiamine (Vitamin B1)
High dietary sulfur promotes ruminal H2S production, which inhibits thiamine-dependent enzymes and causes cerebrocortical necrosis (polioencephalomalacia).
Question 2: Which program is used in the US to eradicate bovine tuberculosis caused by Mycobacterium bovis, and what is the testing method of choice for herd surveillance?
- Federal-State TB Eradication Program using the caudal fold tuberculin test (CFT) (Correct answer)
- USDA Brucellosis Eradication Program using ELISA
- National Animal Health Monitoring System using PCR of nasal swabs
- APHIS-VS program using whole blood interferon-gamma assay only
Correct answer: Federal-State TB Eradication Program using the caudal fold tuberculin test (CFT)
The US Federal-State TB Eradication Program uses the caudal fold test (CFT) for initial herd testing, with positive reactors confirmed by the comparative cervical tuberculin (CCT) test.
Question 3: A cow with a right-displaced abomasum (RDA) complicated by abomasal volvulus is most likely to present with which set of electrolyte and acid-base abnormalities?
- Hypokalemia, hypochloremia, metabolic alkalosis (Correct answer)
- Hyperkalemia, hyperchloremia, metabolic acidosis
- Hyponatremia, metabolic acidosis, normal chloride
- Normal electrolytes with respiratory acidosis
Correct answer: Hypokalemia, hypochloremia, metabolic alkalosis
Abomasal outflow obstruction causes sequestration of HCl, leading to hypochloremia, hypokalemia, and a paradoxical metabolic alkalosis with paradoxical aciduria.
Question 4: Which biosecurity measure is most effective at preventing introduction of Johne's disease (paratuberculosis) into a closed beef herd?
- Purchasing animals from Johne's-tested herds and testing all additions (Correct answer)
- Vaccinating all incoming animals with killed M. paratuberculosis vaccine
- Quarantining new arrivals for 14 days in a separate pen
- Testing fecal samples from all animals annually with PCR
Correct answer: Purchasing animals from Johne's-tested herds and testing all additions
Because no test has 100% sensitivity for Johne's disease, purchasing from certified low-prevalence herds combined with pre-purchase testing provides the best risk reduction.
Question 5: A beef producer has a 3% calf crop loss from scours annually. To calculate the cost of a calf scours prevention program, which parameter is NOT included in the basic cost-benefit analysis?
- Breed of the dam (Correct answer)
- Cost of the vaccine program
- Value of calves saved
- Labor costs for treatment
Correct answer: Breed of the dam
Dam breed is not a direct economic variable in a cost-benefit analysis of a vaccination program; the relevant inputs are vaccine cost, calf value, morbidity/mortality rates, and treatment costs.
Question 6: A beef cow herd experiences an outbreak of abortion storms affecting 30% of pregnant cows. PCR testing confirms Neospora caninum. What is the primary route of transmission in cattle?
- Transplacental (vertical) transmission from dam to fetus (Correct answer)
- Ingestion of oocysts from dog feces (horizontal)
- Tick vector transmission
- Venereal transmission from infected bulls
Correct answer: Transplacental (vertical) transmission from dam to fetus
Neospora caninum is perpetuated in beef herds primarily by transplacental transmission; congenitally infected calves become the next generation of chronically infected dams.
Question 7: When using a whole-herd approach to control bovine respiratory disease (BRD) in a stocker operation, what does the term 'pull rate' refer to?
- Percentage of animals removed from the pen for individual treatment due to BRD signs (Correct answer)
- Rate at which calves are pulled from the pasture for processing
- Proportion of animals vaccinated at arrival processing
- Number of cattle shipped per week to slaughter
Correct answer: Percentage of animals removed from the pen for individual treatment due to BRD signs
Pull rate measures the proportion of cattle identified and pulled from pens for individual BRD treatment, serving as a key performance indicator of disease prevalence and health management efficacy.
NAVLE Bovine Herd Health 5
A herd of cattle in the Texas panhandle develops polioencephalomalacia (PEM).
The most common cause in feedlot cattle on high-sulfur diets is deficiency or antagonism of which vitamin?