NAVLE Bovine Herd Health 5

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?

Accepted Answer

Thiamine (Vitamin B1)

Answer

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?

Accepted Answer

Federal-State TB Eradication Program using the caudal fold tuberculin test (CFT)

Answer

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?

Accepted Answer

Hypokalemia, hypochloremia, metabolic alkalosis

Answer

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?

Accepted Answer

Purchasing animals from Johne's-tested herds and testing all additions

Answer

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?

Accepted Answer

Breed of the dam

Answer

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.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Bovine Herd Health 5