Twinning increases with high production

If you think you’re seeing more cows calving with twins, you’re right.

The rate of twinning in Holsteins has more than tripled in the past 25 years.

Cows that produce 40kgs of milk per day or more are predisposed to produce more twin calves than cows with lower production. Research carried out by Paul Fricke, a dairy reproduction specialist with the University of Wisconsin revealed some interesting findings. In today’s highly productive herds, that means most cows can be susceptible to higher rates of twinning. And that’s not a good thing.

Cows that have twin calves are at increased risk for a whole host of problems: Calving problems, retained placenta, metritis, displaced abomasum and ketosis. They also, then, are at risk for increased days open and more services per conception in their next lactation. These increased risks sum up to greater chance of early retirement and culling.

The resulting twin calves don’t fare very well either. Twin calves are at higher risk of abortion, stillbirth

and reduced birth weight because of shorter gestation length. For those twins who survive, they are then at a disadvantage to grow and thrive into adulthood. Heifers born twin to bull calves are almost always infertile.

While there may be a genetic predilection for twinning in the Holstein breed, most of the problem has to

do with low progesterone levels at the time of ovulation. And that is being driven by the high rate of feed

intake high producing cows need to sustain stratospheric levels of milk production.

High producing cows will eat well over 22kgs of dry matter per day, and well over 45kg of feed on an as-fed basis. These high rates of feed intake increase blood flow through the liver, which in turn reduces the amount of progesterone circulating in the blood. Low progesterone, in turn, results in higher rates of double ovulation. Double ovulation does result in higher conception rates, but also more pregnancy losses – and more twins.

The key point is the level of progesterone produced by the cow herself and it has a more negative effect as milk yield rises. At about 40 kilograms of milk production, about 25% of cows double ovulate. At 50 kg of milk production, more than half of cows will double ovulate.

The fix to the problem is two-fold. The first is strict adherence to heat synchronization protocols. Using synchronisation programs correctly will not increase the rate of twinning, however, using them incorrectly

has been shown to increase twinning.

For those farms that use a Pre-Synch/Ovsynch program and cherry pick cows to breed based on heat detection, about half of the cows not detected in heat will start the Ovsynch protocol in a low-progesterone environment. These cows have an increased risk of double ovulation and twinning, particularly now that a lot of units are now giving the second prostaglandin treatment in the Ovsynch protocol.

The bigger problem comes in the resynchronization of open cows after breeding. Ten to 25% of these cows at re-synch don’t have a corpus luteum (CL) and are in a low progesterone environment when they are found empty at preg check. At preg check, if a cow does not have a CL, the recommendation is to treat the cow with GnRH and then inserting a progesterone device for one week to increase progesterone levels during the protocol. After seven days, remove the device and proceed with the rest of the OvSynch protocol. That should reduce the rate of double ovulation and the chance of twins.

Cows that have been identified as carrying twins should be managed differently to try and reduce the potential risks involved before calving. These cows in many cases calve in early, so drying off 10 days early and closely monitoring body condition score is essential. Some producers will move these cows straight to the close up pen for the duration of the dry period, although this will vary depending on the make up of the diet. Always consult your veterinarian and nutritional advisor to help set up a plan to suit your individual herd needs.