PSP60 profile and its variation factors and application to twinning diagnosis in a beef suckling herd

PSP60 kinetic and its variation factors were studied in a beef suckling her d from 1296 peripheral concentrations recorded on 203 single and 47 twin pr egnancies from the 3(rd) to the 9(th) months of gestation. Number of fetuse s and parity of dam are significant factors of variation (p < 0.0001). PSP6 0 kinetic can be simply described using a linear model of the logconcentrat ion against time with an homogeneous slope whatever the parity and the numb er of fetuses. The corresponding diagnosis of twinning can be carried out b y a single PSP60 assay performed between 140 and 180 days of gestation, or using the average value of several assays performed during gestation. The v alues of sensitivity (predicted twin outcomes/observed twin outcomes) are t hen 77% and 81% respectively using those two procedures, and corresponding values of specificity (predicted single outcomes/observed single outcomes) are 76% and 77%. Predictive values of twin diagnoses (true twin predictions I expected twin outcomes) are 41% and 45% respectively. Corresponding valu es far single diagnoses are 93% and 94%.