Pregnancy diagnosis in pigs: A field study comparing linear‐array real‐time ultrasound scanning and amplitude depth analysis

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Abstract
Between days 24 and 32 after mating/insemination, 881 pigs (785 pregnant and 96 not‐pregnant) were tested for pregnancy on a commercial farm with a linear‐array real‐time ultrasound scanner. 5–7 Days later, 785 of these animals (708 pregnant and 77 not‐pregnant) were tested again with A‐mode equipment by farm employees. Confirmation of pregnancy was based on recorded farrowings or abortions: confirmation of non‐pregnancy was based on return to oestrus and rebreeding, recorded non‐farrowing, or inspection of the uterus of culled animals at the slaughterhouse. From the number of correct positive (a), incorrect positive (b), correct negative (c) and incorrect negative (d) diagnoses, a sensitivity (a/a + d) of 100% versus 97.5%, a specificity (c/c + b) of 90.6 versus 55.8%, a positive predictive value (a:a + b) of 98.9% versus 95.3% and a negative predictive value (c:c + d) of 100% versus 70.5% were calculated for the real‐time ultrasound technique versus A‐mode technique. It was concluded that real‐time ultrasound scanning provides a very accurate technique for pregnancy diagnosis in pigs, enabling immediate decision making on treatment or culling of animals diagnosed as non‐pregnant.