is route

3 October 1997

Good technique

to help embryo

is route

survival

Benefits of careful handling, feeder design and factors

influencing embryo survival were among the topics reviewed

at pig breeding company JSRs annual technical conference

at Sutton Bonington, Notts. Jonathan Riley reports

EMBRYO losses in pigs – which can be as high as 27% – could be reduced by adapting management techniques.

Speaking at JSRs annual technical conference at Sutton Bonington, Cheryl Ashworth, senior research scientist at the Rowett Research Institute, Aberdeen, said that feeding, breed, and ambient temperature influence embryo survival rate.

In trials at the Rowett, gilts offered feed at 3.5kg/day prior to mating, had a higher ovulation rate and better embryo survival than gilts fed 1.15kg/day.

These gilts then either remained on the higher feed rate or were dropped to the lower rate.

"Embryo survival rates were highest when gilts were switched from high rates before to low rates after mating," said Dr Ashworth.

Service regimes can also be manipulated to increase embryo survival.

"For example, mating gilts before their third heat reduces embryo survival. And mating regimes which ensure that semen deposition occurs 10 to 12 hours before ovulation – usually early on the second day of the heat – provide better fertilisation rates than those when service is 20 hours after ovulation. In this case only 32% of embryos may survive.

Ambient temperature should also be controlled immediately after mating; temperatures of 32C (89.6F) on day 8 to 16 can reduce embryo weights and increase mortality. Lack of space and aggression also increase embryo mortality.

In addition to the effects of management on embryo survival, studies of the Meishan pig at the Rowett have also shown that peculiarities in hormone secretions within the womb ensure higher survival.

"Embryos develop at different rates and this is one reason for embryo mortality. Larger embryos begin secreting hormones which are toxic to the smaller, less developed embryos.

In the Meishan, embryos begin secreting the hormone more uniformly than in modern hybrids, so more embryos survive and the Meishan produces larger litters.

CUT EMBRYO LOSSES

&#8226 Keep temperatures below 32C (89.6F) immediately after mating.

&#8226 Serve gilts at or after their third heat.

&#8226 Ensure semen deposition occurs 12 hours pre-ovulation.

Timing of hormone secretions from developing Meishan embryos differs to modern hybrid stock. This allows better survival rates and hence, higher litter sizes.