“In a New Zealand cow, the rumen is packed tight with grass. There’s not even room for a hanky at the top. If you add straw to that it will be mixed in with all the rest and just take up space where the grass could be.
“As well, overseas, cows on 26kg DM will also consume about the same weight in water. A cow in NZ on 18kg DM of grass will be consuming about 100-120 litres of water. And the water passes through them very, very quickly.
“They feed straw overseas because they believe it makes the cow ruminate more, producing more saliva which neutralises the rumen’s pH. In NZ we have so much water going through anyway because of the wet nature of our grass we don’t need to do that.
“By feeding straw you are decreasing pasture intake and so decreasing the metabolisable energy and so decreasing milk production.
“And the belief that cows will eat straw if they need it is wrong. Cows don’t know what’s good for them. They’re just inquisitive. They’ll eat anything.”
Farmer thinking was also challenged on how to feed cows about to calve. “The advice we have been giving you for years on how to feed springer cows is wrong,” Roche said.
“We used to tell you to feed them as well as you could but you shouldn’t.”
He said recent research carried out in this country and overseas showed limiting intake to 90% of what cows had been fed during the winter made the animal begin to mobilise body fat.
“If you get them to mobilise a little bit of body fat for the two weeks before calving it seems to set the liver up better to be ready to do it after calving,” he said.
“Then you will get fewer metabolic problems.
“It’s also the only thing I know that will slow the rate of body condition score (BCS) loss after calving. Whatever you feed them after calving won’t make a difference but restricting them 1-2kg before calving will. And you can do it by adding straw to stop them pacing the fence lines,” he said.
‘Some of the problem is, because we’re feeding fodder beet through the winter now, we are seeing some really fat cows at calving.’
“Some of the problem is, because we’re feeding fodder beet through the winter now, we are seeing some really fat cows at calving,” Gibbs said.
“If they have a BCS of more than 5.5 at calving, you are going to have cows going down.”
“It’s because when they mobilise their body fat after calving, it has to go through their liver,” Kay said.
“If there is too much fat, the liver can’t handle it and then there are problems with glucose production.”
“The rate of ketosis doubles in cows with BCS of between 5.5 and 6 compared with cows under 5.5. At 5.5 they will give more milk than cows at 5 but cows at a BCS of 6 give no more milk,” Roche said.
On questions about feeding minerals they advised farmers to stick with cheaper inorganic trace elements.
“Organic trace elements are grossly overpriced and inorganic are just as good,” Roche said.
“And don’t let anyone tell you otherwise. If they do, send them back down your driveway.”
He said minerals should be fed two weeks before calving and for about five months following calving.
“We often don’t know if they are deficient,” he said.
“A cow can be compromised for a long time before she shows clinical signs.”
Kay said more research needed to be done on whether feeding grain and other concentrates before mating improved conception rates.
“There has been a lot of NZ work, which showed the same results as that of a UK study, that increasing the starch and therefore the glucose did bring forward cycling by eight days and did increase the six week conception rate but when it came to pregnancy testing there was no difference to the cows which were not fed the grain,” she said.
“We think the extra glucose may be detrimental to embryo survival.”
“However, if you are underfeeding your cows and you add grain you will see a reproduction response,” Roche said.
“If you are feeding your cows 18kg DM of good pasture and they are leaving residuals of 1500-1600kg DM/ha then they are eating everything they can. If you add grain to that, you will see a small response in the vat, but most of that will be volume, and your cows will leave more pasture behind and then you get quality issues. It’s about how much time you want to spend on your tractor.”
The FeedRight Roadshow is travelling the North Island in March. For more information visit www.dairynz.co.nz
