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When the heat is on, there’s less pregnancy loss

Establishing the level of estrus activity at joining could help lift fertility and – most importantly – decrease the rate of pregnancy loss.

Texas A&M University Department of Animal Science assistant professor Ky Pohler told the 2020 Genetics Australia online conference that late embryonic or early fetal loss – about day 45 to 60 – was extremely costly for beef and dairy producers.

“The cows go a lot of days with us believing they are pregnant...and then we have to revert all the way back to the beginning to restart the process,” he said.

Using data from dairy cows which received a single artificial insemination in a fixed time joining program, Dr Pohler showed how most of the time fertilisation was not the main limiting factor in embryonic loss in a lactating dairy cow  – rather it was the time post fertilisation.

At day 28 – when a pregnancy can be first detected via ultrasound – there was a 30 per cent loss, according to Dr Pohler. These animals “recycle” back and are bred at the next estrus.

Those with a detected pregnancy at day 28, up to 12 per cent go onto loose this pregnancy – characterised as late embryonic loss – in the coming weeks.

From day 45-60 it is “pretty safe” to maintain the pregnancy going forward.

Dr Pohler said similar results were evident in beef cattle.

Embryonic losses where reduced when cows and heifers were joined when they had a stronger estrus.

The strength of the estrus – or heat – was determined by the amount of scratching on an Estrotect breeding indicator patch attached to the animals.

Those which had 50 per cent or more of the patch surface area scratched, had increased pregnancy rates at day 30, Dr Pohler said.

The pregnancy loss in the cows with less than 50 per cent of the surface area scratched- defined as no or low estrus – was higher.

Dr Pohler advised farmers to breed cows with the no or low estrus to conventional semen – rather than more expensive sexed semen – or beef semen to limit losses and acknowledged more work was needed in this area.