Accuracy of ultrasonography for pregnancy diagnosis on days 10 to 22 in heifers.
Two operators independently conducted ultrasonic pregnancy examinations on nulliparous Holstein heifers on Days 10, 12, 14, 16, 18, 20 and 22, and assigned a diagnosis (pregnant or nonpregnant) and a score for degree of certainty in the diagnosis (1, 2 or 3 for low, intermediate or high, respectively). Pregnancy was retrospectively confirmed by the ultrasonographic detection of an embryo proper and embryonic heartbeat on Day 24 in 20 25 bred heifers; the five nonpregnant heifers were excluded from the analyses. Eleven nonbred heifers were included as an unequivocal source of nonpregnant heifers. Accuracy was not significantly greater than a guess (50%) before Day 18, but reached 100% on Days 20 and 22. Mean accuracy was higher (P<0.005) for nonpregnant (65 77 , 84%) than pregnant heifers (91.5 140 , 65%). For certainty score, there were main effects of day (P<0.0001), reproductive status (pregnant or nonpregnant, P<0.003), and an interaction of day and reproductive status (P<0.0001). The certainty score increased in all heifers among days and was higher (P<0.05) in pregnant than nonpregnant heifers on Days 16 to 20. For luteal area (area of corpus luteum, excluding area of fluid filled center, if present), there were significant main effects of day, reproductive status and a day by status interaction (P<0.0001 for each). Luteal area was approximately constant in pregnant heifers, but in nonpregnant heifers it was lower (P<0.05) on Days 16 to 22 than on Days 10 to 14. Uterine echotexture was scored on a scale of 1 to 3, characteristic of a diestrus, intermediate and estrus uterus, respectively. There were main effects of day and reproductive status (P<0.0001 for each) and an interaction of day and reproductive status (P<0.025). Uterine echotexture was approximately constant in pregnant heifers, but in nonpregnant heifers it was higher (P<0.05) on Days 16 to 22 than on Days 10 to 14. Pregnancy diagnosis on Days 10 to 14 was based on detection of the conceptus; however, detection of the conceptus was not accurate prior to visualization of the embryo proper (mean Day 22, range Days 20 to 24). In nonpregnant heifers, a correct diagnosis with high certainty was made when a small corpus luteum and uterine echotexture characteristic of estrus were detected. In the absence of these changes on Days 18 to 22, a diagnosis of pregnancy was made with high accuracy and intermediate or high certainty.
Kastelic
J P
JP
Department of Veterinary Science University of Wisconsin-Madison Madison, WI 53706 USA.
Curran
S
S
Ginther
O J
OJ