Is grass worth the hassle in spring?

Torrential rain over much of the country last weekend forced cows indoors on many farms. Further rain during the week made matters worse. Ground conditions are often challenging at this time of year and achieving two bouts of grazing in each day is a big challenge and takes a lot of effort, even on dry farms. The question is, is it worth the effort?

The first thing to say is that Irish dairy farmers have invested millions in animal housing, slurry storage and making and storing silage. These investments have been made to protect the land and to be able to carry cows over the winter months. If ground is too wet to be grazed, then using the available sheds is the right thing to do.

However, from a feeding point of view, giving milking cows silage comes at a big cost and its not just the cost of silage relative to grass, it is the cost of lost output when silage is fed. This is because silage is a low energy and a low protein feed and cows have a requirement for high energy and high protein.

Even good quality silage is relatively low in energy so when milking cows are fed silage their overall energy intake declines and they go into negative energy balance.

This is where cows use up their own body fat reserves because they are not getting enough energy in their feed for milk production and body maintenance.

In the same way that people who want to lose weight go into a calorie deficit, feeding silage to milking cows effectively puts those cows in a calorie deficit.

At this time of year, feeding cows is a juggling act between getting grass in the diet while minimising poaching and keeping cows well-fed while achieving good grass utilisation. On top of this, workload is almost at peak in terms of calving and calf rearing so time is at a premium. It’s also fair to say that for a lot of farmers there are pressures outside of farming, such as family time or sport which adds a few more balls into the air.

Increasingly, I hear farmers say that they are prioritising things other than grass in early spring. In other words, they will graze when conditions are good, but are no longer doing on/off grazing or bringing in cows in the evening. Each farmer has his or her own priorities but those that make the effort at getting some grass into the diet of milking cows in spring should be well rewarded for doing so.

In Ireland, the energy content of feed is measured in UFL, with 1kg of barley equal to one UFL on an ‘as fed’ basis while in Northern Ireland and elsewhere feed quality is measured in metabolisable energy (ME). Table 1 lists the typical dry matter, energy and protein contained in commonly used feeds on dairy farms.

When looking at the table, it’s important to note that the analysis is based on a kilo of dry matter basis, not on an ‘as fed’ basis. This is to make it easier to compare the energy levels in different feeds. So while 1kg DM of barley contains 1.16 UFL, if 1kg of barley was fed as is, it would supply the animal with 1 UFL.

Look at the energy levels in grazed grass in springtime. At 1.06 UFL per kg DM the energy levels in spring grass is far higher than any of the silages. Maize silage is often considered a high energy feed and it is high energy when compared to other silages. The best quality maize at 33% starch is at 0.93 UFL, but only a very small proportion of maize grown in Ireland would ever achieve that level of starch. More typical maize at 25% starch contains 0.8 UFL, less than the 0.85 UFL contained in top quality grass silage at 75% DMD.

Fodder beet at 1.12 UFL is a high energy feed and it’s the only bulky feed that surpasses grass in terms of energy content per kg DM. However, like maize and to a lesser extent grass silage, fodder beet is low in protein at just 8% while grass silage is typically around 11% crude protein.

The ideal protein content in the diet of dairy cows is 15%, so when cows are fed silage, maize or beet the protein content in the concentrate needs to be well above 20% in order to balance the diet. Whereas spring grass at 20% to 25% crude protein supplies excess protein.

Consistently under-feeding cows by not supplying enough energy and protein in the diet leads to excessive body condition score loss and a reduction in both milk yield and milk protein per cent. Tirlán have identified the differential between fat and protein per cent as an indicator of under feeding and will alert suppliers when the fat to protein ratio goes above 1.4. The fat-to-protein ratio is worked out by dividing the fat content in the milk by the protein content.

The desired fat-to-protein ratio for Holstein Friesian cows is between 1.2 and 1.4 with ratios above 1.4 indicating that the herd could be underfed. It’s likely that Jersey crossbred herds have a higher threshold, probably more like a ratio of 1.5 before it becomes concerning. In Tirlán’s analysis of herd performance, where cows are pinched in the spring, overall milk production on the farm is substantially reduced. Protein per cent in the milk is very responsive to energy intake. So when silage is fed, or when cows graze stemmy grass in summer the protein per cent will usually drop.

Previous research by Teagasc showed that even when cows are fed a high quality TMR diet in spring, it takes eight weeks after turnout for milk protein to recover to the level achieved by cows that were on a grass and concentrate diet since calving.

The weather is outside farmers’ control and to a large degree so too is land type. But there are things that farmers can control when it comes to feeding cows in spring.

Calving date and stocking rate have a huge impact on grass availability per cow.

As herds calve more compactly, delaying calving date to match grass supply may be necessary while matching stocking rate to grass growth will make it easier to keep grass in the diet.

Ensuring there is enough grass on the farm in spring by closing at the correct cover in the autumn is also key.

So too is investing in infrastructure to enable early turnout such as good access to paddocks through roadways and fencing.

What this shows is that grass and a couple of kilos of meal is best in class when it comes to feeding cows in spring. Obviously, that is not always possible every day or every week depending on ground conditions and weather. It is when cows have to be housed for prolonged periods that the quality of the alternative feeds comes into play. For most farmers, targeting 75% DMD grass silage for these periods and 5kg or 6kg of meal will be the best alternative.

Getting some grass into the diet, for even one grazing per day will be a big help at upping the energy and protein in the diet. Feeding typical quality silage of 68% DMD is hugely damaging to milking cow performance, particularly if it has to be fed in late March when cows will be heading towards peak production.