How much ration to feed this summer?

With plentiful grass, the question on many farmers’ minds is how much meal should they be feeding? With a high milk price and a moderate concentrate price, the economics of meal feeding is weighing on people’s minds.

The good news is that there is no need for pseudo-science when it comes to making these decisions around concentrate use during the summer months, as there is plenty of good science which allows farmers to make informed decisions.

Response

Before looking at the response to meal, we need to look at the response to grass as there is far more of a difference in response to grass than there is to meal.

Presuming ryegrass dominates the sward, the big thing is the pre-grazing yield. This has a huge impact on the quality of the grass as higher covers have more stem and less leaf. This makes sense as higher covers contain taller plants and taller plants need more support, hence they have higher percentages of stem.

This has an impact on quality, which is best measured in energy or UFL. Each 1kg DM of grass at a cover of 1,400kg DM/ha contains 0.93 UFLs, while 1kg DM of grass at cover of 1,800kg DM/ha contains 0.89 UFLs.

Given that a dairy cow requires 0.45 UFLs for every litre of milk produced, consuming 18kg of grass at 1,400kg pre-grazing yield means there is the potential to do 24l/day after taking off her requirements for maintenance.

If the cow ate 18kg of grass at a pre-grazing yield of 1,800kg DM/ha then she would only have enough energy to produce a little over 22l per day – a difference of 2l/day compared to grazing at the correct cover.

But that’s not the end of the story because there is also an intake effect when cows are grazing higher covers. All that stem in the sward with the higher yield takes a lot longer to digest in the rumen and intestines compared to the rapidly digestible grass at lower covers.

This means that when cows are eating stemmy grass they feel full faster and so their overall intake reduces. This is good news if you want to put cows on a weight-loss diet, but bad news if you want cows to produce high levels of milk. All else being equal, extra milk can only be produced from extra intake so high intakes are essential for high yield.

The difference in intake between grazing covers at 1,400kg and grazing covers at 1,800kg can be as high as 2kg DM/day. This means that rather than eating 18kg of high-quality grass, cows grazing high covers only eat 16kg of low-quality grass – a double whammy.

Rather than producing 24l/day from grass, cows grazing these high covers will be more likely to be producing 18.3l/day from grass, which is over 3.5l/day of a difference. This really emphasises the importance of focusing on the correct pre-grazing yield during the summer months.

The flip side is that the response to concentrate will be greater when the quality of the pasture being offered is lower. This stands to reason because there is a big difference in quality between meal and poor-quality grass, but very little difference in quality between meal and high-quality grass.

We often hear it said that responses in the order of 1kg of milk for every 1kg of meal fed is possible, but to do so would mean that the quality of the grass would need to be very poor. This is why response to concentrates is high in indoor systems or where there is a lot of silage being fed. It would be far more beneficial for the farmer to focus on improving grass quality, as the primary feed before feeding extra meal because the response is good.

The typical response to concentrate in mid-season when grass quality is good is more like 0.75kg of milk for every 1kg of meal fed. At a meal price of say €330/t fresh weight, which is €388/t on a dry matter basis, each 1kg DM of meal costs 39c. At a milk price received of say 55c/l, at the above response rate the return would be 41c in milk for every 39c spent on meal.

Historically, this is actually a very high return, even though it’s marginal, as there is usually a negative economic return from feeding meal during the summer. However, feeding any more than 1.5kg of meal per cow per day when grass is plentiful still doesn’t make sense, as it puts grass quality at risk.

We know that when cows are fed a lot of supplement the post-grazing sward height increases. In other words, cows get lazy and refuse to graze down into the butt of the sward when they can get feed easier in the milking parlour. This has a negative impact on subsequent grass quality and yield, so almost by accident, grass quality declines when a lot of meal is fed. This has the effect of reducing the quality in the overall diet so milk yield will drop, eroding the advantages of feeding meal in the first place and reversing any economic benefit.

High intakes

The key take home for me is that high intakes of high-quality grass are the way to maximise profit this summer, not by feeding higher rates of meal or by taking the foot off the pedal with residuals. When it comes to ensuring high intakes, there are a number of things that farmers need to be aware of that limit intake.

The first is the strip wire or inappropriate-sized paddocks. While strip wires might help to ensure a good sward cleanout, it does so at the expense of grass intake because cows need to work hard at every grazing. Younger and less dominant animals tend to suffer under such scenarios.

Contrast that to the optimum scenario where cows have access to 36-hour paddocks where they get two grazings with no limitations and just work hard to get a good clean-out on the last grazing. In this situation animals are much freer to express their potential intake and are moved on when the desired residual is achieved.

The second issue for the mid-season is stocking rate. This is crucial because setting the stocking rate too high will limit the amount of grass that cows can eat. If this is restricted, then milk yield will suffer.

On average, daily grass intakes are higher now than they were 10 years ago because cows are producing more milk solids per day. While before we would have presumed cows ate 18kg DM/day across the board, we are now seeing more and more farmers back-calculate overall intakes of clover to 20kg DM/day.

This means that if a farmer expects to grow 65kg/ha/day on average over the next six weeks and if the grass allowance is say 19kg, then the maximum stocking rate can only be 3.42 cows/ha. Otherwise, intakes will be restricted or extra supplement will be required. This is one of the reasons why too much meal is being fed during the summer months.

Comment

I’m all for producing high yields during the summer months but I think many farmers need a refresher on how to do that. The biggest problem right now is that too much meal is being fed and there isn’t enough focus on achieving the correct residuals.

Grass quality (and milk yield and protein per cent) will crash and burn in June and July if residuals are not kept at or under 4cm now. There are over 80 years of scientific research on correct grazing management so we don’t need to reinvent the wheel and the fundamentals haven’t changed because milk price is high.

Cows can still be well fed now but this notion of “letting cows achieve their potential” is rubbish if it means residuals aren’t being met because too much meal is being fed or the farmer doesn’t want to make the cows work hard. Remember, dairy farmers farm grass number one and cows number two. All the cow does is convert grass to milk solids so the primary focus should be on grass.