The Use of Linear Array Real-Time Ultrasonography for Pregnancy Diagnosis in Pigs

Abstract

Early detection of open females provides an economic basis for pregnancy tests on pig farms. Oestrus detection alone will not enable the identification of all nonpregnant females because nonpregnant pigs may fail to show subsequent oestrous behaviour due to prolonged cycle lengths, silent oestrus, anoestrus or cystic ovaries. On well managed pig farms with farrowing rates higher than 80%, it can be expected that 5–10% of the animals which do not return to oestrus at 3 weeks post mating or insemination will be nonpregnant. This means that the costs of any pregnancy “test” other than oestrus detection, rest upon a relatively small portion of all anoestrous sows that have to be tested. Therefore, a pregnancy test should be highly relaible in order to be profitable. It has also been (theoretically) calculated (van der Steen, 1985) that a negative pregnancy test arround day 35 of gestation which will not be followed by therapeutic measures such as induction of oestrus, is only of economic interest when farrowing rate are lower than 80%; it may, however, lead to a reduction in net return (returns minus costs, labour included) at higher farrowing rates. So both the accuracy of pregnancy diagnosis and decision making on the basis of this test are of outmost importance.