SAC says late embryo losses on the increase
LATE embryo losses that occur between 18 and 60 days after cows are served are on the rise, claims Peter Ball of the Scottish Agricul-tural College, Auchincruive, Ayr.
"In the 1970s, 5-10% of pregnancies resulted in late embryo or early foetal losses. Now the figure is 15-20%," says Dr Ball. "These reproductive losses are of economic concern."
In SAC studies embryo losses are detected using milk progesterone profiles which show that the cow has been pregnant but is no longer so. But these are expensive for on-farm use.
Dr Ball claims part of the reason for the rise in embryo losses could be diseases such as leptospirosis, infectious bovine rhinotracheitis or bovine virus diarrhoea. Early embryo loss is also thought to be associated with the stress of modern milk production.
"High genetic merit cows have a higher energy gap in early lactation that can affect fertility," he says. Social stresses in housed animals could also be a factor.
"Try to avoid sudden changes in the early stages of pregnancy such as moving animals between groups. And try to prevent this period coinciding with housing or turnout."
When a pregnant cow is inseminated there is a 50% chance of her aborting, warns Dr Ball. This can be avoided using a cow-side milk progesterone test before AI.
"Once a cow is in her fifth lactation she is more likely to suffer embryo loss," he says. "Conception rates remain the same, but she is less likely to maintain the pregnancy."
The older cows uterus may be less able to sustain pregnancy or her hormone signals may be weak.
To ensure good fertility, Dr Ball advises milk progesterone pregnancy tests 21 days after service, and scanning after 28 days. But cows can still return between 28 and 60 days, so a pregnancy diagnosis at 72 days by scanning or a manual PD is also advised. *
• Keep herds disease free.
• Use milk progesterone tests to check for pregnancy.
• Avoid stress for 60 days after service.
AVOIDING EMBRYO LOSS
Peter Bull:"Avoid sudden changes in the early stages of pregnancy."