More milk with grass

High digestibility equals a higher feed intake.

In order to achieve high feed intake, organic matter digestibility of pure grass should be between 78 and 81%. If there is between 30 and 50% clover in the clovergrass mixture, we need "only" 76-80% digestibility of the organic matter as clover passes more rapidly through the rumen.


Photo: Erik Nissen

If we want to understand what affects organic digestibility of grass, we must go to the cellular level and see how the grass plant cells are built.


A plant cell may be divided into cell content and cell wall:

The content of the cell consists mainly of protein, crude fat, starch and sugars, all of which have a constant and high digestibility close to 100%, see table below.

This means that the cell content in general has a constant and high digestibility.

 

Nutrients

Digestibility

Cell content

 

Crude protein

High – constant

Crude fat

High – constant

Sacharides

100%

Fructanes

100%

Starch

Close to 100%

Cell wall

 

β-glukanes

100%

Pectines

100%

Cellulose

Variable

Hemicellulose

Variable

Lignin

0%

Source: Rudolf Thøgersen – SEGES – DLF Grassland conference 2015.

In the cell wall, which consists of β-glucanes, pectines, cellulose, hemicellulose and lignin, it is quite different. Pectines and β-glucanes have a high digestibility (100%), while the digestibility of lignin is 0%. The digestibility of cellulose and hemicellulose varies, which means that the digestibility of these components in practice are determent for the overall digestibility of grass.

Hemicellulose and cellulose together with lignin is what we often refer to as the cell wall (NDF). Summed up, a high digestibility of NDF (DNDF) is synonym with a high digestibility of organic matter. The content of NDF can be determined by analysis. The digestibility of NDF (DNDF) is calculated from the content of NDF.


More Milk with high DNDF Varieties from DLF

The digestibility of cellulose and hemicellulose depends, among other factors, on cutting time, weather and fertilisation, but we have also seen a difference between grass varieties, when they are compared under the same growing conditions. At DLF we test all varieties for feeding value, and those showing to be above average concerning digestibility of NDF (DNDF) are marked with a milk glass.


High digestibility = higher feed intake

A high digestibility the grass provides a higher feed intake, more milk in the tank and at the same time you can save on expensive purchased feed supplement. Livestock Consultant Niels Martin Nielsen, Agro Limfjord in Denmark, has calculated what it means for milk yield and the balance per cow when feeding grass with respectively 72 and 80% digestibility of organic matter.

Feed intake per cow per day

Digestibility (organic matter) in grass silage

72%

80%

Feeding level, kg drymatter

20.9

21.5

Grass silage, kg drymatter

6.0

7.3

Maize silage, kg drymatter

6.3

6.3

Concentrate, kg drymatter

13.5

11.5

Feeding costs, total, €

5.19

4.97

Expected milk yield, kg Energy Corrected Milk (ECM)

39.2

40.0

Margin, €

4.81

5.23

 

A high digestibility of organic matter in grass enables the cows to have a higher feed intake which again results in more milk and reduced costs for bought-in concentrate. The table shows what the impact is on milk yield and the margin per cow per day when feeding with grass where the DOM is 72% and 80% resp. The milk price used is €0.25 per kg ECM and the production price of grass and maize is resp. €0.20 and €0.17 per kg DM.

By increasing the DOM in grass with 8%-points, the milk yield is increased with 0.8 kg ECM per cow per day, when the grass – as in this case – is around 25% of the total feed ratio.

Conclusion: Replacing poor grass silage with some having 8 %-units higher digestibility increases milk yield with 0.8 kg and farmer’s income with €0.4 per cow per day.

Overall, good pasture quality gives more milk in the tank and saves you purchase of supplementary feed. In other words: There is money in finding the right grass mixture, where you can reap a high yield of digestible grass. DLF varieties with high digestibility of the cell walls (DNDF) is a good starting point for this - look for milk glass, this is your guarantee for sound and sustainable varieties.