Retrospective evaluation of the results of embryo transfer, or insemination with sexed and traditional semen in heifers at an American Holstein-Friesian dairy farm

Background: Assisted reproduction techniques (ART) like using frozen or sexed semen for artificial insemination and embryo transfer are getting to be wide-spread. Objectives: The objective of our study was to evaluate the practical results of embryo transfer and artificial insemination with normal frozen and sexed semen. Materials and methods: A retrospective survey was conducted at a large-scale Holstein-Friesian dairy farm in Wisconsin in 2017 involving 1,475 heifer calvings, of which inseminated with normal frozen (CON-MT) and sexed semen (SEX-MT), and mated with embryo transfer (EMB). Gestation length, birth weight, weaning weight, calving difficulty, sex ratios, abortion, stillbirth, and neonatal death rates were compared. Results and discussion: Gestation length was 276.5 days in the CON-MT, 275.3 days in the EMB, and 273.8 days in the SEX-MT group. Male calves had one day longer gestation length than female ones. Sexed semen yielded 88.1% heifers, compared with 51.8% for embryo transfer and 47.3% for conventional semen. Dystocia was 17.6% in the EMB, 9.4% in the CON-MT, and only 4.3% in the SEX-MT group. Stillbirth rate was low in all cases: 4.8% in the EMB, 1.0% in the CONMT, and 0.7% in the SEX-MT group. Birth weight was higher with 2.3 kg in the EMB than that in the CON-MT group, and 3.3 kg heavier than that in the SEX-MT group. Male calves were on average heavier with 2.8 kg than female calves, but there were no significant differences between them. Female calves in the EMB group were heavier with 1.7 kg than those in the CON-MT group and heavier with 2.1 kg than in the SEX-MT group. The abortion rate was the highest (4.4%) in EMB, and it was only 1% in CON-MT and 0.7% in the SEX-MT group. These results show that using assisted reproductive techniques in combination on the dairy farm can be an effective way to reach outstanding breeding efficiency. However, the relatively high abortion rate, stillbirth rate, birth weight, and calving difficulties require further studies to evaluate factors influencing these parameters and the means for additional improvements.