8 October 1999

High-merit beasts andembryo losses

HIGH genetic merit cows are no more likely to suffer embryo losses between 50 and 80 days than lower yielding contemporaries, according to Irish research, despite anecdotal evidence suggesting otherwise.

Teagasc Galway researcher Joe Sreenan told the British Society for Animal Science conference that producers say more embryos are dying in later stages in higher merit cows. But this anecdotal evidence is not supported by research.

"The embryo survival pattern is exactly the same in high merit cows as in medium merit cows and heifers in the herd. Where producers are intervening in the belief that cows are losing embryos they are trying to solve a problem that isnt there, and wasting money."

He cited research that suggests embryo death is about 38% of fertilised embryos, indicating that losses are a major concern. But 70-80% of losses occur between day eight and 16 after insemination. A further 10% are lost between 16 and 42 days, and just 5-8% after 42 days.

Dr Sreenan believes information on the timing of embryonic deaths and embryo growth and viability will help reduce losses in future.

One such issue already identified is that reduction in energy intake, even for a short period after insemination, seems to have a serious adverse effect on embryo survival.

But there is no evidence to support theories that this is an interaction with hormones or that its a direct cause of ammonia and/or urea levels seen in blood or milk.

A study of the effects of feeding high nitrogen pasture showed increased ammonia and urea levels, but this did not reduce embryo survival rate in heifers, he said.

He advised that whatever the level of energy feed try to keep it as constant as possible before and after insemination and during early embryo development.

Dr Sreenan suggested that producers may believe more embryos are lost at a late stage because more heats are unobserved. This could be a factor of increasing herd size and reducing labour, giving less time for important jobs such as heat detection. But a cow producing high peak yield at this time is also under pressure and may show fewer signs of heat.

EMBRYO LOSSES

&#8226 Late losses not increasing.

&#8226 Keep energy feed constant.

&#8226 Dont worry about urea.

&#8226 Improve heat detection rate.