Twin pregnancy diagnosis in Holstein cows: discriminatory powers and accuracy of diagnosis by transrectal palpation and outcome of twin pregnancies.

The objective of this prospective cohort study was to determine the sensitivity, specificity, accuracy, and predictive value of twin pregnancy diagnosis by rectal palpation and to examine fetal survival, culling rates, and gestational lengths of cows diagnosed with twins. In this prospective study, 5309 cows on 14 farms in California were followed from pregnancy diagnosis to subsequent abortion or calving. The average sensitivity, specificity, accuracy, and predictive value of twin pregnancy diagnosis were 49.3%, 99.4%, 96.0%, and 86.1%, respectively. The abortion rate for single pregnancies of 12.0% differed significantly from those for bicornual twin pregnancies and unicornual twin pregnancies of 26.2% and 32.4%, respectively (P < 0.05). The early calf mortality between cows calving with singles (3.2%) and twins (15.7%) were significantly different (P < 0.005). The difference in fetal survival between single pregnancies and all twin pregnancies resulted in 0.42 and 0.29 viable heifers per pregnancy, respectively. The average gestation for single, bicornual, and unicornual pregnancies that did not abort before drying-off was 278, 272, and 270 days, respectively. Results of this study show that there is an increased fetal wastage associated with twin pregnancies and suggest a need for further research exploring management strategies for cows carrying twins.