Conception rate in Holstein dairy cows having both normal sized follicles and cystic follicles at estrus

Abstract

ObjectiveTo investigate the conception rate when cows showing clear signs of estrus and having both normal sized follicles and cystic follicles were artificially inseminated. MethodsThirty parous Holstein cows showing clear signs of estrus and having both normal sized follicles (diameter <25 mm) and cystic follicles (diameter ≥25 mm) simultaneously in their ovaries were artificially inseminated. Changes in the ovaries were observed using real-time ultrasonography for 25 d after artificial insemination. The concentration of plasma progesterone (P4) was measured simultaneously to monitor the function of the corpus luteum. ResultsThe normal sized follicles ovulated in 21 out of 30 cows (ovulation rate: 70.0%), and 11 of these cows successfully conceived (conception rate: 36.7%) (Group C) while 10 cows did not conceive (Group NC). The maining 9 cows, normal sized follicles did not ovulate (Group NO). The change in P4 in cows that ovulated was similar to that in normal cows. Although there were no significant differences in median number and size of cystic follicles among the groups, all cows in Group C only had one cystic follicle. ConclusionThese results support artificially inseminated of cows that show clear signs of estrus even if they have both cystic follicles and normal sized follicles, and especially when the cows have only one cystic follicle.