highlighted that conception rates were, on average, poorer
with sexed semen compared with conventional semen,
but these trials also noted large herd to herd variation.
For example, in the 2018 trial a quarter of the herds had
better conception rates with sexed semen compared with
Last spring a controlled trial involving 2,250 cows on 24
farms was carried out to examine the importance of timing
of AI when using sexed semen. The results were published
at the Teagasc Dairy Open Day, Moorepark in July. Teagasc
researcher Dr Stephen Butler said: "The most recent field
trial was undertaken to investigate if timing of AI relative
achieved with sexed semen. We compared AI using
conventional semen or sexed semen at two di erent times
relative to a controlled time of ovulation."
injection of GnRH is given to control timing of ovulation,
allowing AI at a fixed time 16 hours later, regardless of signs
of heat. High fertility cows were identified in each herd,
and were synchronised using a fixed-time AI protocol and
inseminated by an AI Technician 16 hours after final GnRH
injection with conventional semen (CONTROL-16) or sexed
semen (SEXED-16), or with sexed semen at a delayed time
(22 hours after final GnRH injection; SEXED-22).
All cows were scanned for pregnancy diagnosis 35 to 40
days after fixed-time AI. Overall, the conception rate to first
service was 61.1 per cent, 49.0 per cent and 51.3 per cent
for CONTROL-16, SEXED-16 and SEXED-22, respectively.
Conception rates achieved with conventional semen were