Establishing the level of estrus activity at joining could help lift fertility and most importantly decrease the rate of pregnancy loss, according to an American professor.
Texas A and M University Department of Animal Science assistant professor Ky Pohler presented at the Genetics Australia 2020 virtual series recently and noted that cows with late embryonic loss or early fetal loss, about day 45 to 60, were extremely costly.
"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 on to lose this pregnancy - characterised as late embryonic loss - in the coming weeks. Dr Pohler said the period of pregnancy loss was similar between beef and dairy cows.
In beef cattle, despite research showing Bos indicus-influenced cattle having a higher pregnancy loss early in gestation, there was no difference in the sub species when it came to late embryonic mortality (LEM).
"One of the things that is very surprising, but very repeatable, is heifers are experiencing a lot more LEM and pregnancy loss after the day 28 or 30 pregnancy check compared to any of our other age categories," he said.
When looking at what controls pregnancy loss, Dr Pohler said both female and male contributions need to be considered.
Measuring the level of estrus activity could help improve pregnancy rates, while decreasing pregnancy loss, according to Dr Pohler.
"Ten years ago we started scoring heat detection (Estrotect) patches on a four point scale - one being 0 to 25pc, two 25 to 50pc, three 50 to 75pc and four 75 to 100pc," he said.
"Scores one to two show low or no estrus level, and three to four shows high activity and estrus activity."
Dairy data out of Brazil indicated pregnancy rates at day 32 were higher in score three and four animals, compared to those that did not show estrus. Day 60 showed a similar trend, and pregnancy losses were seen to be higher in animals that did not show estrus.
Dr Pohler had been giving the reproductive tract a size and position score at the time of artificial insemination or embryo transfer.
If the entire tract is on top of the pelvis it is a score one, if the cervix is up but the horns are down below the pelvic floor it is a two, and a three score is when the entire reproductive tract is hanging over the pelvis floor. Regardless of age, research showed females with smaller tract scores had increased pregnancy rates.
