IVF calves are more likely to be dopier
CALVES produced from laboratory (in-vitro) fertilised (IVF) embryos are twice as likely to be larger than average and 10 times as likely to be dopier than calves from natural reproduction.
That said, Dr George Seidel of the Colorado State Universitys Animal Reproduction and Biotechnology Lab, US, told the MIlan Fertility Conference that the calves would develop normally -but require extra care in their first few days of life.
About 1%-2% of calves from IVF embryos would be heavier than average – weighing about 54kg-59kg (120-130lb) at birth compared with 36kg-45kg (80-100lb).
More common was incidence of "dopey calf" syndrome, with about 10% of IVF embryos producing such calves. This compares with normal reproduction which produces about 1-2% of doppy calves, especially in pedigree herds.
"These dopey calves fail to get up and nurse and need good management early on," he said.
Dr Seidal said extra risk of "dopiness" with IVF calves could be because the calf is one of the 1%-2% that are larger at birth -and a difficult calving might make it weak. But a more likely reason was that the placenta had failed to develop normally.
Based on evidence from human IVF, Dr Seidal believed the placenta could be transporting too much energy-rich glucose to the calf. This would explain its large size in some cases – and the dopey effect in others. Once born it suffers a large energy drop and lacks vigour. *