Serving cows who are likely to take longer to cycle – such as heifers – ahead of the rest of the herd could tighten calving pattern, an international fertility expert told Co. Down farmers.

Qualified vet and reproduction specialist Joyce Voogt from LIC travelled from New Zealand for a series of talks run by AI Services and Teagasc. Voogt is the firm’s international technical manager.

She addressed farmers at a fertility day held at the Rankin family’s farm in east Down earlier this week.

Tightening the calving pattern

“To get your in-calf rate target you need to get a 90% submission rate and 60% conception rate – and do that for the first two cycles – if you’re going to hit the 70% six-week in-calf rate,” she said.

Getting those cows mated early and calving down early in the calving block is really the biggest driver of a good calving pattern and reproductive sustainability – which is why we worked so hard on it [on our own farm].

Voogt said heat detection aids as simple and inexpensive as tail paint could be a useful tool for gathering information on the herds’ fertility to make decisions on which cows should be served earliest.

“Mating your heifers ahead of your cows is becoming more common in New Zealand,” she said.

“It was always done that way; it got let go for about 10-15 years, but people are going back to that because it takes them a bit longer to have a first cycle – about 10 days on average longer than a cow.

“So if you are doing that – mating them a week ahead of the main herd – then you should be aiming for 83% calving in the herd’s first three weeks.”

The concept was met with mixed response with some local farmers saying this could pose labour problems. However, others did seem more intrigued.

Studies on fertility

Voogt added: “In New Zealand we had a lot of farmers saying cows were calving earlier – and we were hearing this again and again – so we did a big study and looked at the national database to see just how fast cows were calving now compared to what they were 10 or 15 years ago.

“We found that, on average, cows in New Zealand are calving one day earlier. It used to be 283 days; now it’s 282 days.

Then we looked at distribution – calves are not like Swiss trains that always arrive on time; they don’t read the schedule and know ‘I’ve got to be born on this day’. They have a natural distribution of birth-date around the expected calving date.

“95% of calves will be born within plus or minus nine days of their expected calving rate and that is also true for the shorter gestation lengths as well.”