Dexcel Extended Lactation Project

February 2005
New Zealand Friesian cows have been bred to get in calf every year, be very aggressive grazers, good walkers and good producers on the mainly pasture feeding system. The traditional spring calving twice-a-day whole milking system that has been in use for half a century or more and is etched in cowshed concrete. However, in recent years some farmers have been breaking with tradition. First came the re-introduction of winter milk and split herd calving, then the unthinkable once-a-day milking regime, and now Dexcel is exploring another idea that in Kiwi terms is beyond the pail.

What would happen if you milked cows for two seasons in a row without calving before the second season? What would happen to production levels? Would the cows cope better or worse? Would some cows do better than others on such a regime? Could it be done on an all-grass system or would heavy use of concentrates be necessary? And anyway, why would you want to?

Scientists at Dexcel are running a proof of concept trial looking at extending the lactation of dairy cows to two seasons without calving (ie. milking continuously for almost two years). A herd of 56 Holstein-Friesians, half NZ genotype and half US genotype are being run together, and fed one of three feeding regimes:

  • All grass

  • Grass plus 3kg concentrate/day

  • Grass plus 6kg concentrate/day

Now towards the end of the second year there are some fairly clear observations:

  • As expected, the US genotype are producing better than NZ ones

  • Cattle are in very good condition

  • Although milk production dropped in winter it bounced back in the second spring

  • Milk protein levels are now higher, making the milk more valuable

  • Results overall are positive and should justify taking the project to the next stage

A big chunk of costs on farm is associated with trying to get cows in calf, health problems around calving, labour for calving and calf rearing, and cow wastage (cows which don't get in calf have to be culled). If the costs and stress of calving was only every second year that might represent a considerable saving. It might also be good for the cows not to have the stress of the second pregnancy while milking, and of calving itself.

On the other hand, you would have to milk continuously for more than double the normal period, possibly having to feed cows more during the winter. Production might go down in the first winter and stay down. Then theres the wear and tear of daily walking and milking on the cows.Extended lactation regimes overseas indicate that it is possible under grain-feeding systems with their stock, but NZ stock might not perform well.

Dexcel designed an indicative study using 56 Holstein-Friesian cows of two genotypes NZ and USA and fed on three different regimes all grass, grass plus 3kg concentrates, grass plus 6kg concentrates. The study was to answer the questions:

  • What does an extended lactation look like and is it feasible under NZ conditions?

  • When do cows start dropping out?

  • How much do we have to feed to keep them producing?

They were calved in July 2003 and run together as one herd. So far only six have been dried off, and the rest have been milked twice daily for 550 days, about twice the normal lactation length. As well as production records, blood and milk tests are being taken regularly to look for genetic and other markers that will indicate animals that are particularly suited to this regime.

The main results are:

  • the overseas genotype animals are producing more, as expected, so much so that animals that are being fed grass and three kilos of grain are still producing more than 2 kg of milk solids per day at present which is not much less than they were producing at this time last year.

  • for a number of treatments cows are following a similar lactation curve to last season with a fall-off over the winter and the second peak in spring.

  • an unexpected result is that for the last six months milk fat to protein ratio has been 1:1 ie. Production of as much protein as fat, around 4.2% instead of the usual 3.5%. Protein is the more valuable component of milk.

  • even the all-grass cows are still producing around 1 (NZ) and 1.3 (US) kg of milk solids per day
    all cows have put on body weight since calving and only one group (US on 3kg conc.) is below 5.0, which is the target score at calving.

  • the NZ genotype is bred for grass feeding and tends to put on excess weight if fed the high level of grain or milked longer than a 300-day lactation. Some are obese (condition score 8.6), but all the rest are in healthy condition and should get in calf and calve successfully.

  • The all-grass cows have a current condition score of 7.1 for NZ and 6.1 for US, which are both very good

Eric Kolver, senior scientist, dairy cattle nutrition, says that these results indicate that extended lactations are feasible under NZ conditions, but a lot more work needs to be done to refine the system and test profitability. Once they have the full two years of data, the next steps will be:

  • Use the Dexcel Whole Farm model to predict the profitability of the regime and a number of variations.

  • Use the animal data to find predictors of animals that will thrive and produce well under extended lactation regimes.

He cautions that a workable and profitable regime for a commercial dairy farm could be four years away, and it will suit only a proportion of farms and will not be universally applicable. However, some of the possibilities could be calving cows in the spring and milking them for two years, calving half the herd every year and milking that half herd for two years, split calving in autumn and spring and having an 18 month lactation for each group and milking once a day over the winter when milk volumes drop, then go back up to twice a day in the second spring.