Progesterone level can predict risk of embryo loss in dairy cows
Take Home Message: Higher progesterone concentrations on day seven post insemination can be used to predict cows at risk of early embryo loss.
Early luteal concentrations of progesterone were a reasonable predictor of concentrations on day seven and could be used to predict animals at risk of embryo loss.
Just one of the interesting findings of a trial, carried out by scientists in Ireland, to establish the relationships between plasma concentrations of progesterone (P4) during the early luteal phase and subsequent embryo survival rate.
“We also wanted to find out more about the repeatability of P4 concentrations during the early luteal phase from cycle to cycle in dairy heifers,” explained Teagasc’s Mervyn Parr, speaking at this year’s British Society of Animal Science’s annual conference, held at Queen’s University, Belfast.
In cattle, early embryo death is a major cause of cow reproductive wastage. Low post ovulatory systemic progesterone (P4) or a delay in the normal increase in P4 concentrations during the early luteal phase have been associated with reduced embryo survival rate in dairy cows.
So, to find out more, the team synchronised oestrus in 118 Holstein-Friesian heifers using two injections of a synthetic prostaglandin administered intramuscularly 11 days apart.
At the oestrus following the second injection, heifers were artificially inseminated (AI) by one of two operators using thawed frozen semen from one high fertility bull. Embryo survival was determined by ultrasonography on day 30-35 after AI.
A positive pregnancy diagnosis was based on the presence of an apparently viable foetus with a visible heartbeat and clear amniotic fluid. Following pregnancy diagnosis all heifers were injected with synthetic prostaglandin to induce embryo loss and return to oestrous cycles.
Six weeks after the induced embryo loss, the entire experimental protocol was repeated on all heifers. All inseminated heifers were blood sampled twice daily (am and pm) on days four, five, six and seven following each insemination.
Concentrations of P4 were determined by radioimmunoassay and a mean concentration of P4 was calculated for each day.
“And we found that there was both a linear and quadratic relationship between concentrations of P4 on days four to seven and changes in P4 between these days and embryo survival rate,” said Mr Parr.
“Increasing concentrations of P4 were associated with increasing embryo survival rates although embryo survival declined at very high concentrations of P4. Early luteal phase concentrations of P4 had a low repeatability from cycle to cycle,” he added.
Presented to the British Society of Animal Science Annual Conference, 12-14 April, 2010, Queen’s University, Belfast.
Parr MH, Mullen MP, Crowe MA, Roche JF, Lonergan P, Evans ACO and Diskin MG: “The relationship between plasma progesterone concentration during the early luteal phase and embryo survival in dairy heifers.”
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