What question did this study set out to answer?

This research aims to compare gestation length, calving difficulty, birthweight, and early life health of calves from embryos fertilized with conventional or sex-sorted sperm.

May 31, 2026Open Access

Gestation length, calving characteristics, and early life health of calves born following transfer of fresh in vitro-produced embryos generated using conventional or sex-sorted sperm

Key Points

This research aims to compare gestation length, calving difficulty, birthweight, and early life health of calves from embryos fertilized with conventional or sex-sorted sperm.
Collected oocytes from elite beef and dairy heifers and cows for four weeks.
Fertilized oocytes with frozen-thawed conventional or sex-sorted sperm and transferred embryos to lactating dairy cows.
Analyzed gestation length, calving difficulty, birthweight, and health indicators through biochemical tests.
Gestation length was similar for calves from both beef (280.8 d) and dairy (280.6 d) breeds, as well as from conventional (280.8 d) and sex-sorted (280.7 d) sperm.
Birthweight was significantly higher in beef calves (43.3 kg) compared to dairy calves (39.0 kg) and between conventional (39.9 kg) and sex-sorted sperm (42.4 kg).
Calving difficulty scores were comparable across breeds and sperm types, with higher scores reported for induced parturition.

Abstract

The objectives of the current study were to compare gestation length (GL), calving difficulty (CD), birthweight (BiW) and early life health of beef and dairy calves derived from in vitro-produced embryos generated using conventional (CONV) or sex-sorted (SS) sperm.Oocytes were collected once weekly for up to 4 successive weeks from the ovaries of elite beef (Angus, n = 37) and elite dairy (Holstein-Friesian, n = 51) heifers and cows.Oocytes were matured in vitro and fertilized using frozenthawed CONV or SS sperm from a panel of proven fertility bulls (Beef = 6, Dairy = 9).Embryos were cultured in vitro until d 7, at which point blastocysts (n = 468) were transferred fresh to lactating dairy cow recipients that had been synchronized using a progesterone-Ovsynch protocol.Data for individual calves were subsequently obtained for GL (n = 161), CD (n = 135) and BiW (n = 153).Additional measurements were conducted on a subset of calves, which included blood sample collection at d 11 for biochemical and hematological analysis (n = 41) and again on d 26 (n = 34) for biochemical analysis only.The effects of embryo breed (Beef vs Dairy) and semen type used for in vitro fertilization (CONV vs SS) were examined using generalized linear mixed models.Gestation length was similar for Beef and Dairy calves (280.8 d vs 280.6 d), and for calves derived from CONV and SS semen (280.8 d vs 280.7 d).Mean (±SD) BiW was heavier for Beef calves than Dairy calves (43.3 ± 1.0 kg vs 39.0 ± 1.4 kg), while calves derived from CONV semen were lighter than calves derived from SS semen (39.9 ± 1.1 kg vs 42.4 ± 1.0 kg).Calving difficulty scores were similar for Beef and Dairy calves and for calves derived from CONV and SS semen.Calving difficulty was greater, however, in cases when parturition was in-duced compared with spontaneous parturition.Results of biochemical analyses on d 11 and d 26 and hematological analysis on d 11 were within reference ranges available for healthy calves of a similar age.In conclusion, GL and incidence of CD were similar for Beef and Dairy breed calves derived from IVP embryos, as well as calves derived from IVP with CONV and SS sperm.Birthweight was greater for Beef calves than Dairy calves.Blood biochemistry and hematology variables were similar for calves derived from IVP embryos for Beef and Dairy breeds and for calves derived from IVP embryos that had been fertilized with CONV and SS sperm.

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