Shortening dairy cows’ gestation by 10 days
It’s called SGL semen, it’s been 15 years in the making, and it’s set to provide New Zealand dairy farmers with one million extra days in milk in the first year alone.
Every seasonal dairy farmer has some late cows, and now the use of induction to manage this issue is no longer acceptable – but what if you could choose a sire whose progeny would naturally arrive early?
This was the question on my mind in the late 1990s, and I asked LIC scientist Dr Anne Winkelman ‘what is the heritability of gestation length?’ She replied, “about 0.48 I think”, before turning to her files to check.
The penny dropped. With the high heritability of gestation length, short generation interval, and a single trait focus, we could make solid progress in breeding for that one trait, so LIC’s R&D team modelled the expected output, and soon after, outlier sires and dams were selected for an embryo transfer programme.
We hedged our bets by exploring potential shortcuts. Inseminations with Lowline Angus sires did not bear out the claims, and although the semen from pure Yak bulls delivered on gestation length, conception rates were appalling.
Meanwhile, progress with selecting New Zealand dairy cattle to breed the line of bulls that focused on the gestation length trait continued unabated, and the product was tested in commercial herds.
This year a team of bulls, called SGL Dairy, is available and in addition to offering all the benefits of ease and convenience that comes with the fresh semen service, the bulls will deliver a 10-day advantage on-farm.
Cows that are mated to these sires will calve down an average 10 days earlier, providing the opportunity for longer lactations.
With more than 100,000 pregnancies expected this spring, that’s a million days in milk.
How long is that? Well, if a cow was milked for a million days, it would have started more than 700 years ago.
Farmers who have participated in trials report easier calving, along with the faster recovery of dams pre-mating, and fewer carryovers – but bloodlines with a shorter period of gestation have not been selected for breeding replacements, so the progeny are not to be reared for the milking herd.
The advice for farmers is to switch to SGL semen as soon as enough pregnancies have been created by sires breeding replacements and LIC’s technicians will take care of the rest.
As SGL dairy and replacement calves look just the same, a simple solution is to calve down a separate mob of cows whose last insemination was to SGL, but don’t wait too long to create it as you can expect some calves more than two weeks early.
Experience shows that farmers who use the service are very keen to do so again because shorter gestation length is a benefit which is highly visible before the following mating season, whereas milking traits are not measurable for three years after insemination.
A second team of bulls, known as SGL Marker, combines the most elite genes in shorter gestation length with outlier Herefords to produce progeny with a white face to make identification easy.
The first crop of these new sires will start semen production this year and limited quantities will be available, in fresh form, currently offering about five days advantage on-farm.
We are thrilled to see the SGL project finally deliver on its promise. Good things take time, and this one has been well worth the wait.
Seasonal pastoral dairying is different to the systems practiced elsewhere in the world and sometimes we need to find our own solutions.
Peter Gatley is General Manager of Genetics, LIC