Winter grazing of forage crops is very harmful to the environment, says an AgResearch scientist, Professor Richard McDowell.
They need to be dried off early to reach the recommended 5.5 body condition score (BSC) for first and second year calvers, as compared to the 5.0 BSC for mixed age cows, Haultain told a recent discussion group at Clevedon.
As a rule of thumb it takes 30 days for cows to gain 0.5 BCS but, on average, to take a cow from 4 to 5 BCS it takes 80 days, he says. The maths here does not add up but that is because we need to factor in periods of little to no body condition gain.
There is a 10 day period of zero at drying off. “You try to wind the cow down as soon as you dry her off to slow the metabolism down and shut the udder down and as a result feeding levels are insufficient for body condition gain.”
In the last 30 days before calving there is effectively no gain because the energy requirements of the pregnancy are so high it has all gone to the calf.
With different feed types cows put on condition at different rates. It takes about 130kg of palm kernel above maintenance grass over 80 days to gain one condition score. It takes about 160kg of maize and 200kg of pasture. Autumn pasture is not good for putting condition on which is why farmers often struggle to meet targets at calving.
If the cows are calving in mid-July they need to be at a body condition score of 5 in mid-June. A cow at 4 now she needs to be dried off.
He heard recently from animal welfare officers that they often get more cases of cows in poor condition in spring following a good autumn than a poor one. Farmers carry on milking them for too long and they don’t reach BCS targets.
The good performing farms get high in-calf rates, good six-week in calf rates (78%) and good days in milk driven by meeting BCS targets.
A study of profitable farms across the country showed setting sensible targets and achieving them is a key to their success, Haultain says.
“They are making the farm do what it is actually capable of and it sets it up for the next year and for the next stage in the season. They set sensible targets for body condition score and pasture cover.”
Most farmers would have an idea in their head about what their targets should be, but they need to work out if it is sensible for their farm.
They need to have an average pasture target for balance date and a plan for the start of calving from where they are today.
“It gives us an idea of how much supplementary feed we need to have on hand to achieve these targets and what the target actually is,” he says.