Download maize silage sampling and interpretation of analysis

MAIZE SILAGE
SAMPLING AND INTERPRETATION OF ANALYSIS
Silage Sampling
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Sampling should be conducted at least six weeks after harvesting to ensure fermentation has completed. Sample early in the week and post
for next day delivery.
Provide as much of the additional Information required by the input sheet, as possible, to assist the analysis and interpretation of a seasonal
picture.
On Farm Sampling
 Visualise a ‘W’ pattern on the face of the silage clamp. Take at least 9 samples from 15 – 20cm behind the face at different horizontal and
vertical positions on this ‘W’. Only sample areas where mould is present if these areas of the clamp will be fed.
 Preferably samples should be prepared by ‘Quartering’; tip the sample onto a clean board and thoroughly mix it. Using a piece of clean
board, divide the sample at right angles into four piles to achieve a final sample size of 0.5kg. Place the entire 0.5 kg sample into a clean
plastic bag and ensure as much of the air is removed, as possible.
For further information see the Forage Analytical Assurance Group website - http://www.faagroup.co.uk/
Interpretation of Maize Silage Analysis
Term
Implication for Rationing
Typical
Range
Dry Matter
(%)
The quantity of material left in a feed after all the water has been removed by drying. The value is corrected to
allow for losses of volatile but nutritionally valuable nutrients during drying, e.g. volatile fatty acids. Low dry matter
silages tend to be extensively fermented and will be high in acids and low in rumen structure, reducing intakes.
High dry matter silages are more susceptible to spoilage (bacterial and fungal).
This is calculated from the total nitrogen content of the silage multiplied by 6.25 as the average nitrogen content of
protein is presumed to be 16%. This value provides no information on the quality of the protein in the silage.
24 - 35
D Value (%)
A measure of the digestible organic matter content in the dry matter. This value is inversely related to the crop’s
stage of maturity at cutting.
67– 78
ME (MJ/Kg)
Metabolisable Energy – a measure of the energy content of the feed available to the cow after losses in, faeces,
urine and methane. It is predicted from the ‘D value’.
10.5 – 11.5
pH
A measure of the acidity or alkalinity of the silage; pH < 7 = Acidic, pH 7 = Neutral, pH > 7 = Alkaline. Where the pH
of maize is above this range, typically as a result of poor or secondary fermentation, undesirable VFA’s may have
been formed and production may be reduced.
3.6 – 4.0
Protein (%)
1/3
7–9
MAIZE SILAGE
SAMPLING AND INTERPRETATION OF ANALYSIS
NH3-N of
Total N (%)
When feeding out, products such as ‘Regulator Feed Out’ can be incorporated to reduce further heating and
mycotoxin binders e.g. Ultrasorb, can be used to minimise the mycotoxin challenge. Conversely feeding more
acidic silages, typically from harvesting immature maize, may impair rumen performance, resulting in acidosis,
lower intakes and production. Feeding rumen buffer products such as Acid Buf® can help to alleviate this problem.
Ammonia is by-product of protein breakdown. This value is virtually irrelevant to maize silage when compared to
grass silage, as its protein content is proportionally much lower. Care should be taken in interpreting this term as it is
a percent of total N and not a percent of the dry matter.
0-4
Ash (%)
A measure of the total mineral content.
Starch (%)
Starch is the primary energy source of maize silage and the key reason for growing maize, the content varies
according to, cob size, number of cobs per plant, the maturity of the crop at harvest. The rumen availability of
starch decreases as the maturity and dry matter of the maize silage increases.
Neutral cellulase gammanase digestibility. This is an enzyme-based technique used to estimate digestibility.
25 - 35
NDF (%)
The Neutral Detergent Fibre value indicates the total fibre content of the plant and includes the hemi-cellulose,
cellulose and lignin residues. High NDF levels are associated with mature crops at cutting.
35 - 45
ADF (%)
The Acid Detergent Fibre value is similar to the NDF but only measures the amount of cellulose, lignin and lignified
nitrogen in the silage. The ratio of ADF to NDF is indicative of the proportion of digestible fibre in the forage.
20 - 28
MPB (g/kg)
Maize Silage is not grown primary purpose not a bypass protein source. Metabolisable Protein from Bypass Protein
(also called DUP). Protein which is protected from degradation in the rumen. This fraction is important when
rationing high yielding dairy cows as the rumens supply of metabolisable protein for milk production is limited. The
MPB content of the ration should be increased to reflect greater milk yields using products such as SoyPass®.
15 - 25
MPN (g/kg)
Metabolisable Protein supply from the silage where rumen nitrogen (protein) is limiting. It is typically greater than
MPE as rumen energy is usually the limiting factor in a ration. High levels of MPN in the ration can, indirectly,
negatively influence fertility.
40 - 60
‘sN’ ‘aN’
‘bN’ ‘cN’
Rumen degradable fractions; these values measure the instantly soluble (sN), rapidly degradable (aN) and
potentially degradable (bN) protein fractions of the silage. The rate of fermentation of the potentially degradable
fraction (bN) is described by ‘cN’.
The ‘Metabolisable Protein supply where rumen energy is limiting’. The energy for the rumen microbes is provided
by the sugar, starch and fibre components of the silage and tends to be the limiting factor in rationing.
NCGD (%)
MPE (g/kg)
4-5
2/3
60 - 70
N/A
75 - 90
MAIZE SILAGE
SAMPLING AND INTERPRETATION OF ANALYSIS
‘sDM’ ‘aDM’
‘bDM’ ‘cDM’
Rumen degradable fractions; these values measure the instantly soluble (sDM), rapidly fermentable (aDM) and
potentially fermentable (bDM) dry matter of the silage. The rate of fermentation of the potentially fermentable
fraction (bDM) is described by ‘cDM’.
Lactic Acid
(g/kg)
The main acid produced during the natural fermentation of sugars in well fermented silage. Poor preservation
results in higher levels of undesirable acetic and butyric acids from secondary fermentation. Lower levels are
associated with restricted fermentation e.g. wilted and chemically restricted.
Intake (g/kg
ML)
A relative indication of how much silage a standardised cow will eat by choice. It is influenced by a mix of the dry
matter, crude protein, digestibility, fibre fractions, VFAs and ammonia N concentration of the silage; typically,
higher intakes are indicative of higher quality silages. Dry matter, digestibility and protein are positively related to
intake. The Feed into Milk ration program converts this value into specific intakes for the cow being rationed.
100 - 120
Rumen
Stability
Value
An indication of how stable the rumen will be when fed the silage, it is calculated from the NDF and Potential Acid
Load (PAL). Silage with low RVS’s values may reduce the pH of the rumen, leading to acidosis and reduced
intakes. The Feed into Milk ration program considers this in conjunction with other ration components and cow
details to predict the overall effect on rumen health.
320 - 380
FiM PAL
(meq/kg)
The Potential Acid Load represents the silage fermentation acids, those produced by the rumen micro-organisms
during digestion and any other feed components e.g. amino acids. Rations containing a high PAL content will
typically have a low RSV.
700 - 1000
3/3
N/A
25 - 50