10 May 1996

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. &#42