John Roche said the claims made by South Canterbury arable farmer Jeremy Talbot that DairyNZ has not followed up on research that suggests feeding cows a more “balanced” diet of pasture and other feeds, including maize and cereal, were wrong.
He also denied Talbot’s assertion that DairyNZ’s was actually to blame for some of the environmental problems being laid at dairy farmers doors, such as nitrate leaching, due to the high protein levels of a purely pasture diet.
Roche said DairyNZ was a supporter of pasture plus systems of farming, that is ones that put pasture first but then also used supplements as just that, to supplement the grass diet.
It did not tell dairy farmers they should all be using a pasture only diet and had done plenty of research into getting the best out of a pasture plus method of farming.
Talbot is part of a group of scientists and farmers who have questioned current and past research into reducing the environmental impact of dairy farming.
He said by using a new computer model that can predict an animal’s emissions based on feed intake, along with established rumen science, then also looking at growth patterns and protein levels for pasture and other feeds under current management conditions, then comparing them with what the animal can actually use, “we find that there is an answer as to why we now have a huge nitrate and nitrous oxide increase in our environment that is greater than the increase in stock numbers alone.
“But by also taking this a little further and looking at how we can overcome this, we find that we can also reduce significantly our reliance on irrigation, produce more milk and also milk of a higher value that is also more suited to making the higher value products such as cheese and butters.”
The answer lies in balancing the protein levels in the rumen, he said, adding that it is accepted that cows cannot use more than 16 to 17 per cent protein and “it would seem that the protein levels in the grass vary from month to month but from 18 per cent to over 34 per cent.”
Talbot said the computer model showed that when protein grass levels are around 23 per cent, nitrates excreted in dung and urine are around 400 grams per cow per day, rising to around 1000 grams at 30 per cent of protein in the grass.
“An animal on a high protein grass diet is a bit like a human on a protein only diet and with the same result – weight loss, diarrhoea and lethargic performance,” he said.
The solution, Talbot said, was to grow either maize or whole crop cereal silage on around 10 to 20 per cent of the farm. That was because the maize and whole crop silages were low in protein and high in carbohydrates and fibre, which would balance the very high grass protein.
“Maize and to a lesser extent cereals need the higher temperatures and sunlight to produce the high tonnages, which is why they grow best in summer months when grass doesn’t.”
Using the system he was advocating would allow the operation of dairy systems that do not destroy the environment, he said, as the problem would be reduced by almost 80 per cent.
Roche said millions of dollars in recent years to evaluate systems that were both profitable, while also reducing farms’ environmental footprints “and to claim we haven’t is wrong”.
He said DairyNZ’s approach was that pasture came first and it was important that it was utilised, and to not utilise feed that was already being produced on farms would be “economic suicide”.
However, that could be managed with feeding supplements at the appropriate time.
Roche said debate over how to best feed cows had been going on for a very long time and unfortunately some of the important stuff gets lost as people get polarised.
There was a very good argument that the perennial ryegrass and clover pasture on New Zealand farms was the most balanced feed a dairy cow could eat.
It contained the same energy density as wheat or maize, although the energy came from the fermentation of fibre instead of grain.
On top of that the composition of protein is ideal to maximise milk production.
It was also important to remember that for every tonne of barley that was brought onto a property there was a corresponding extra 15 to 20 kilograms of nitrogen produced, he said, “and that extra nitrogen has to go somewhere”.
Roche said Talbot’s claims about DairyNZ’s approach and research were unfair and Talbot had never been to see him to discuss it.
DairyNZ is a non-commercial organisation and farmers could be confident that its advice, on pasture or any other subject, is evidence based and provided by researchers whose work was peer-reviewed.
The organisation advocated the best solution for each farm and no two farms are the same.
Talbot said pasture first is a good system and New Zealand was fortunate that it had that in abundance.
Link: http://www.guardianonline.co.nz/farming/pasture-first-not-dairynzs-focus/