How to improve silage intakes

Published 4 July 14

How to improve silage intake potential?

Luppo Diepenbroek, independent farm consultant, looks at how to improve silage intake potential by reducing protein breakdown, without compromising fermentation or silage stability.

When comparing analysis for silages cut in May 2012 and May 2013 (see table 1), you can see that average energy content (expressed as ME – MJ/kg) and average intake potential (expressed as grams per kg of metabolic liveweight – g/kg MLW) both increased.

May-12

Mean

Min

Max

 

May-13

Mean

Min

Max

Dry Matter %

38

20

54

 

Dry Matter

36

24

44

Intake Potential

111.48

95.82

125.00

 

Intake Potential

123.16

111.63

125.00

ME

11.33

10.81

11.85

 

ME

11.89

10.41

12.16

Table 1: Courtesy of Sciantec Analytical Services Ltd, Bracknell.

The table shows there was a 0.56MJ/kg ME, or 4.9%, increase in energy level, and an increase of 11.68g/kg MLW or 10.48% in the intake potential of the grass silage.

Two-thirds of the average production increase of 1.5 to 3 litres of milk per cow, seen during last winter, can be attributed to raised intakes on May cut grass silages, as they make up the majority of grass silages made for winter feeding. Around a third of the growth can be attributed to the increase in energy levels, as grass was cut at a younger, more digestible point in time.

There is no direct link between energy levels and intake potential and, unlike many people assume, there is no link between sugar levels and energy levels either. High sugars do not necessary make for palatable grass silages. However, they do help in the rapid fermentation of the grass to make stable silage.

In MDC’s three-year project,  which finished in 2001, it was decided to include intake potential as a value on silages analysed via Wet NIR (Near Infra-Red), following beef cattle intake studies at DANI Hillsborough, and dairy cow intake studies at the SAC. This data, gave a very strong correlation (88%) between the wet NIR determined intake potential and animal grass silage intakes. The spectrum of compounds, identified as being responsible for reduction in intakes were amides and amines. They are protein breakdown products, and smell like “rotten cabbages” or “rotten fish”. Therefore, the intake potential is largely related to protein breakdown.

How do we reduce protein breakdown and henceforth increase silage intake potential? To do this, we need to prevent silage from rotting. Rotting is aerobic (with aid of air) and is also called composting, whereas the aim of silage is anaerobic fermentation, leading to a stable fermented (pickled) product.

Once grass is cut, it dies and stops forming protein, and starts respiration, ie burning sugar and breaking down protein. The breakdown of protein is even quicker in the field if the grass has contact with the soil. That is why a high ash content in the silage is detrimental, as soil contains billions of microscopic organisms in each 1cm³ of soil that are composters (ie break down organic matter and protein). It is therefore important to keep the grass from coming in contact with the soil.

After about 21:00 in late May, you will notice dew starting to descend and it will not burn off until between about 08:00 and 10:00 in the morning. During this period wilting is not taking place but rotting may well be. The exception to this rule is when temperatures are cold enough for these processes not to occur (which they were at the end of April/early May this year).

I saw a solution to this recurring “rotting” problem during a farming study trip to the Waiberhoeve Research Farm in Holland in 2010. Here, Jan Bloemert, farm manager, described how he made his excellent grass silage in the 12 hours of daylight. He achieved a 40% DM silage by cutting between 05:00 and 09:00, and picking up between 17:00 and 22:00. Jan used information from the local weather station, which gave him two-hourly forecast on weather conditions. The main points of interest for him were evaporation rates, which have more to do with wind speed than sunshine!

As well as cutting the grass during the daytime, and tedding twice to achieve a 40% DM, the grass barely touched the soil, as it was kept afloat by the tedding, and was not exposed to evening dew. Also, the product was ensiled quickly, from cutting grass to sheeting was only 17 hours. This allowed the grass silage to ferment quickly, which also further reduces protein breakdown.

Sugars are needed to ferment silage, but do you need maximum amounts or just enough to ferment and stabilise the product? See table 2 below on variation of sugar content during the day.

 

Time

Dry Matter

%

WSC (Sugars)

% in Dry Matter

 

06:30

15.75

16.5

 

11:00

23.06

24.7

 

14:00

22.62

23.4

 

16:00

19.23

23.0

 

19:00

16.94

16.1

 

22:00

19.25

12.5

 

 

 

 

 

 

Table 2: Courtesy of Straight Line Nutrition Ltd. Variation in water soluble carbohydrate (sugars) during the day (May 2004).

As can be seen from the above table, sugar content, even early in the morning on a sunny day, is well over 10%, enough to ferment most silage extensively. Why wait and lose some of the sugars in the grass cut at midday, during the night, due to respiration with associated rotting? You can cut early in the morning and pick up silage the same day, in order to have a grass silage that will produce another two or three litres of milk, due to an intake potential increased from 110 to 125g/kg MLW, without compromising sugar levels and silage fermentation.