Fertilization rates and embryonic development in superovulated cattle inseminated in different sites within the reproductive tract

Abstract

Superovulated Jersey and Holstein heifers and cows were bred 9.7 ± 2.7 h after the first observation of estrus with a single dose of frozen semen. Animals were grouped by site of insemination: 1) right uterine horn (n = 5), 2) left uterine horn (n = 4), 3) mid- uterine body (n = 5), and 4) mid-cervix (n = 6). The number of unfertilized ova, normal and abnormal embryos were recorded for each horn at slaughter 115.8 ± 18.6 h after insemination. All viable embryos were cultured in vitro and assessed for development. The overall fertilization rate was 76.8%, with the ipsilateral horn being higher than that of the contralateral horn (P < 0.05). Similar fertilization rates resulted among all treatments except those inseminated in the contralateral horn (P < 0.05). In vivo development of embryos was higher for the ipsilateral horn inseminations than those of the body of the uterus or cervical inseminations (P < 0.05), but it was not higher than the contralateral horn inseminations (P > 0.05). Under the conditions of this study with superovulated cows, these results suggest than 1) spermatozoa migrate from one horn to the other and 2) inseminating too deep into one horn may reduce the chances for concention when ovulation occurs contralaterally.