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Real-time ultrasonography and pregnancy diagnosis in swine^1,2,

W. L. Flowers^*,3, J. D. Armstrong, S. L. White^*, T. O. Woodard^* and G. W. Almond

^* Department of Animal Science, North Carolina State University, Raleigh 27695-7621 and Department of Animal Science, Purdue University, W. Lafayette, IN 47907-1151 and Department of Farm Animal Health and Resource Management, North Carolina State University, Raleigh 27695-8401

^3. Correspondence: phone: (919) 515-4003; fax: (919) 515-4463; E-mail: william_flowers{at}ncsu.edu.

Abstract

Four experiments were conducted to determine the effectiveness of using real-time ultrasonography for pregnancy diagnosis in swine. In Exp. 1, the influence of stage of gestation, type of ultrasound probe, and frequency of ultrasound probe on the accuracy of pregnancy diagnosis was estimated. Specificity was low for both the 3.5-MHz (57.3%) and 5.0-MHz (58.6%) sector probes on d 18, 19, and 20 (P > .54). On d 21 and 24, it increased (P = .05) to 88.0% and 96.0% for the 3.5-MHz sector probe and to 96.0% and 96.0% for the 5.0-MHz sector probe. The probe frequency x stage of gestation interaction was significant for both accuracy and sensitivity (P = .02). Both were higher (P = .05) on d 21 and 24 than on d 18 through 20 using the 5.0-MHz sector probe. In contrast, with the 3.5-MHz sector probe, accuracy and sensitivity were higher (P = .05) on d 24 than on d 21 and better (P = .05) on d 21 than on d 18 through 20. There were no differences in the effectiveness of pregnancy diagnosis using the 5.0-MHz sector and linear probes on d 21. In Exp. 2, 305 sows were scanned with a 5.0-MHz linear probe from d 17 through 58 of gestation. Accuracy and sensitivity were greater than 95% after d 21. In contrast, specificity increased (P = .01) from 50.2% on d 17 through 20 to 72.5% on d 24 through 30. In Exp. 3, 3,003 sows were randomly assigned to be examined with a 5.0-MHz linear probe on d 21 and 28 after breeding or with an A-mode machine on d 28, 35, and 42 of gestation. Accuracy was similar (P = .71) between the two procedures, with an overall mean of 94.5%. However, specificity was greater (P = .01) for real-time than for A-mode. The objective of Exp. 4 was to determine the effectiveness of using real-time ultrasonography for identifying pseudopregnant sows. Two thousand sows that were diagnosed as pregnant on d 28 of gestation were randomly assigned to receive either no further evaluation for pregnancy status (control) or examination with a 5.0-MHz linear probe between d 65 and 75 of gestation. More (P = .01) sows presumed to be pregnant at d 28 failed to farrow in the control treatment (132/905) than in the real-time ultrasound treatment (23/898). These studies demonstrate that real-time ultrasonography is an accurate means of pregnancy diagnosis for swine when used after the first 3 wk of gestation.

^1. The authors are grateful to the commercial swine operations in North Carolina and Paul Gonzalez at N.C.S.U. Swine Educational Unit for their assistance with these studies.

^2. Support for this research was provided by the National Pork Producers Council and the North Carolina Pork Council.