title: Serum urea nitrogen and conception rate: the usefulness of test information.
abstract: Total of 627 AI in 332 Holstein cows in nine herds were used to examine the relationship between serum urea N and conception rate. Cows were assigned randomly to one of three isocaloric diets varying in protein degradability and content. The AI occurred from 50 to 150 DIM. Mean serum urea N for each cow from 50 to 150 DIM was used to examine conception rate and serum urea N. The clinical interpretation of serum urea N on conception rate is evaluated using Bayes theorem from two approaches (dichotomization vs. continuous). Test information resulting from dichotomization of serum urea N into high and low categories (maximizing the average of test sensitivity and specificity) is compared with likelihood ratio approaches allowing a continuous measure. Likelihood ratio test indicates that conception rate decreases with serum urea N of > 14.9 mg/dl, but dichotomized test suggests that the decrease does not occur until serum urea N is > 20 mg/dl.
authors.affiliation: Center for Animal Health and Productivity, University of Pennsylvania, School of Veterinary Medicine, New Bolton Center, Kennett Square 19348.
authors.forename: J D
authors.initials: JD
authors.lastname: Ferguson
authors.forename: D T
authors.initials: DT
authors.lastname: Galligan
authors.forename: T
authors.initials: T
authors.lastname: Blanchard
authors.forename: M
authors.initials: M
authors.lastname: Reeves
mesh_terms: D000818:Animals; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000502:physiology*; D004044:Dietary Proteins / Q000008:administration & dosage; D005260:Female; D005306:Fertilization; D011247:Pregnancy; D012016:Reference Values
chemical_list: D004044:Dietary Proteins