Egg pick-up trebles implant
Co-operatively minded Dutch milk producers are keen to re-invest in dairy genetics and research projects.
Jessica Buss reports
OVUM pick-up is now available to Dutch cattle breeders through Holland Genetics, the marketing organisation for the three main Dutch AI companies.
The technique enables oocytes (eggs) to be collected for fertilisation in the lab (in-vitro fertilisation) and embryo transfer.
"Breeders can now obtain the benefits of breeding from superior cows who respond poorly to super-ovulation using hormone stimulation," says Tho van den Berg, manager of the Al Land van Cuijck AI centre.
The co-op owned company decided to make this technique available after two years development. The advantage of ovum pick-up is that as many as 100 embryos a year can be implanted, compared with 30 a year from super-ovulation, says Holland Genetics Bartele Verbeek.
"In addition each oocyte collection can be fertilised with a different superior sire. This offers more variation in the combination between top cows and top sires."
Frozen embryos produced from eggs collected via ovum pick-up fail to transfer well when thawed resulting in unacceptable pregnancy rates at 35%. As such all embryos are implanted fresh. In farm trials involving 210 cows, pregnancy rates averaged 55%, claims Mr Verbeek.
For successful transfer, the embryo must be implanted in the recipient on the farm within eight hours of leaving the lab.
"The size of Holland and the location of the labs enables fresh embryos to be transported successfully to the recipient animals," says Mr van den Berg.
On average 10 oocytes a cow and eight a heifer are collected in twice weekly sessions (see Livestock, June 16, 1995, for collection technique). After oocyte maturation, in-vitro fertilisation and embryo maturation in the lab for seven days, an average 1.3 embryos a collection are suitable for transfer, says Mr Verbeek. "Successful embryos depend on oocyte and semen quality. The poorest bull fertilised 10.6% of oocytes and the highest 22.3%."
He adds that ovum pick up can also be used in pregnant cows up to four months after conception, without any difference in the quality of oocytes.
The cost of each oocyte collection is £104, and each embryo cultured £62, says Mr van den Berg.
Developed in England
Ovum pick-up has also been developed in England by Genus. Brian McGuirk, breeding programme manager, claims an average of 1.8 embryos have been cultured from weekly collections. But freezing of embryos also resulted in poor pregnancy rates so the technique has mainly been used in their own breeding programmes.
Genus are now researching embryo freezing in conjunction with Holland Genetics. "We are not offering fresh embryo transfer commercially in the UK due to the restrictions on the time of transporting the embryos," he says. He adds if they are successful with embryo freezing then ovum pick-up will be offered commercially by Genus.