A closer look at responses to concentrate feeding at grass
With mid-season grazing rotations now underway, Dr. Joe Patton, Head of Dairy Knowledge Transfer at Teagasc, shared key advice on concentrate supplementation rates.
Joining Teagasc Dairy Specialist, James Dunne on a recent episode of the Dairy Edge podcast, Dr. Patton first acknowledged that meal feeding levels often generate lively debate among at discussion groups, with much of this is driven by discussion of milk price compared to concentrate cost per tonne. However, he also highlighted the importance of considering response rates when farmers are evaluating their meal feeding levels.
Providing a research-backed approach, Dr Patton said that where a plentiful supply of high-quality grass is available, the average response to concentrate in mid-season is around 0.7-0.8kg of milk per kilogramme of concentrate dry matter fed.
“At this response level if you take concentrate at around €300/t and a milk price received of 40c/L, feeding say 1kg in the morning and 1kg in the evening to supply minerals and get cows into the parlour is a good practical option, but it is effectively a breakeven exercise in terms of milk response versus meal cost.”
One reason why milk response rates are limited in a grazing context is that adding additional concentrate to the diet curtails cow active grazing time, with Dr. Patton explaining: “Older research shows that for every extra kilo of concentrate a cow eats, the cow is going to graze for 15-20 minutes less per day.
“If you are feeding 3kg over and above what is needed and looking for a response, the cow’s grazing time is going to be down by an hour in the day, which is going to affect grass intake.”
A key point then discussed was that milk response rates tend to decline as daily meal feeding rates at grass increase, which in turn erodes the prospect of a positive economic return.
“The 0.8 response is an average figure for low to medium feeding rates. As we go up to 4-6kg of concentrate, the rate of milk response to extra kg meal fed will drop. It could be down as low as 0.5kg of milk per kilo of dry matter. So, for example, if you feed an extra 2kg at a 6kg feeding rate, you might only get 1L milk in return and then you are into negative territory.”
Going back to the on-farm discussion of meal feeding rates, the effects of pasture intake and quality play a significant role in response rates but are often overlooked. Ironically, milk responses per kg meal fed tend to be higher where pasture intake is low, but this is no guarantee of a good financial return.
“It probably pays in the short term to feed concentrate if pasture quality is really poor, but it would pay much better to fix grass quality.”
Feeding to a peak
Often aired in discussion groups is the theory of feeding cows on in April and May to reach a higher peak yield. On this, Dr. Patton again reverted to studies from Moorepark:
“There has been a lot of work done on this over the years. We offered higher levels of concentrate feeding in the spring period, assuming that forage and grass were the same, creating a difference in concentrate input. The cows did peak a little bit higher, but as soon as you bring the diets back to being the same, the milk yields will converge quickly through May, June and July.
“Feeding heavily in April and May to drive a high peak in the hope that you will get more milk through the rest of the year – there is no data to support that idea. The idea that you are going to get a big payoff back down throughout the year really isn’t supported.”
Breeding season concerns
For farmers concerned about reducing meal input ahead of the breeding season, Dr. Patton said the key fertility factors are already largely determined.
“What will determine the success of breeding is going to be the body condition of the herd, which won’t be affected by the meal feeding rate in the next week; the genetics of the herd, which won’t be affected by the meal feeding rate in the next week; and also the mineral status,” he said.
“The big things that make a difference to fertility are already locked and loaded. There is no point in feeding for fertility in the first days of May,” Dr. Patton added.
Capitalise on the opportunity
Professor Michael O’Donovan, Head of Grassland Science at Teagasc, also joined the podcast where he reminded farmers that the mid-season period should be viewed as an opportunity to make better use of grass and reduce concentrate feeding where conditions allow.
“This is about opportunity,” he said. “People talk about response to concentrate. From now on, we should be talking about where we are with milk price. In the current scenario, from a farmer’s perspective managing cows, it is about consistency of performance at grass.
“It is about monitoring the pre-grazing yields, making sure they are consistent in terms of intake, making sure the residuals are consistent and reducing concentrate down to a low enough level. If it is going to be 1-2kg to provide minerals, that’s fine. If it is above that and you have plenty of grass, you are basically not making the money that you can make in a low milk price year,” he said.
For further insights, listen to the full episode of the Dairy Edge podcast below: