Repeat breeder tactic
COWS that keep returning to service after artificial insemination may hold when two embryos are implanted by direct transfer instead.
Semex ET vet Peter May claims a pregnancy rate of 54% from implanting pairs of beef embryos into about 50 repeat-breeder cows seven days after natural heat. For this he used the one-step thaw embryos. Cost was £80-£95 a cow.
In Canada Semex has also implanted embryos into repeat-breeders to improve pregnancy rates. It implanted single embryos seven days after service by AI, instead of twin embryos. At 40%, initial conception rates were low but have improved to 60% by implanting embryos in cows that have returned under four times.
Mr May believes that two early embryos, from either technique, send out a stronger signal to the cow to maintain pregnancy than one embryo alone. *