Pregnancy Diagnosis
Pregnancy diagnosis was initially performed 32 d af-
ter TAI for all cows using a portable scanner (Ibex Pro; E. I. Medical Imaging, Loveland, CO) equipped with a 7.5-MHz linear-array transducer. A positive pregnancy diagnosis was based on visualization of a corpus luteum on the ovary ipsilateral to the fluid-filled uterine horn containing an embryo with a heartbeat. Pregnant cows diagnosed with singletons (n = 48) based on transrectal ultrasonography 32 d after TAI continued the experi- ment in which pregnancy status was assessed weekly using transrectal ultrasonography from 39 to 102 d after TAI. Cows diagnosed pregnant based on the presence of an embryo with a heartbeat and then diagnosed not pregnant at the subsequent examination based on the presence of a dead embryo or the absence of an embryo in the previously gravid uterine horn were considered to have undergone pregnancy loss.