Assessing Your Silage Report Silage analysis is a useful if not essential tool when diets are to be formulated for ruminant livestock. All producers s...
Assessing Your Silage Report Silage analysis is a useful if not essential tool when diets are to be formulated for ruminant livestock. All producers should have their pits analysed in order to give them an idea as to what type and how much supplementary feed should be used to ensure satisfactory performance levels. This article will hopefully translate some of the jargon into an understandable format. Dry Matter (DM) Quite simply this is the amount of silage remaining after the water has been removed Water has no energy or protein values so it is ignored. The energy and protein value of silage is quoted as % Dry Matter. The higher the DM the more energy and protein the cow will receive for every kg of fresh silage she eats, everything else is water and she can drink this! In general low DM will limit intakes and high DM will stimulate intakes E.g. cow eats 40kgs of a 20% DM silage and 40kgs of a 25% DM silage both with energy contents of 10.5 MJ/Kg DM. Energy supply from 20% DM silage is 40kg x 20% = 8kg DM x 10.5 = 84 units of energy Energy supply from 25% DM silage is 40kg x 25% = 10kg DM x 10.5 = 105 units of energy 21 units of energy more from higher DM silage or approx. 1 gallon of milk pH A pH of around 3.8 to 4.2 will show silage that is well preserved and will keep well. Wet silage with a high pH will not keep well and is usually accompanied by high ammonia levels, this shows that the silage has not fermented well or contained high levels of nitrogen before it was cut. Intakes of this silage will be low and high ammonia levels can lead to scouring pH values of 3.6 and below are considered to be acidic silage’s and will require careful supplementation and/or buffering to avoid stomach upsets. These silage’s can sometimes be identified by their sharp smell and by cows bringing up a lot of ‘cud balls’. Dry silage’s can have higher pH values and be well preserved such as 4.5 and above
Ammonia N % High ammonia levels shows poor fermentation, this can be due to • high grass nitrogen levels at cutting • or low sugar, young wet grass being cut
Effective additives can help to overcome this problem. More mature, stemmy grass will have a higher sugar content and is easier to ensile than less mature and Italian ryegrass swards < 5% 5 – 10% 10 – 15% 15 – 20% > 20%
excellent fermentation good fermentation moderate fermentation poor fermentation very poor fermentation
Crude Protein This shows how mature the grass was at the time of cutting > 15% very leafy young grass 12 – 15% grass at normal stage of cutting 9 – 12 % mature stemmy crops • • •
Young reseeded swards will tend to have higher protein levels due to the fact that the protein content is higher in the leaf than it is in the stem. Low protein levels can be seen in grass crops growing rapidly in early spring, particularly Italian Ryegrass swards. Inadequate fertiliser applications can also lead to low protein levels
As a general rule of thumb for every % decrease in protein below 16% in silage, meal protein level should be increased a % unit above 18% for dairy cows E.g. 12% CP silage, feed a 21% nut ME (MJ/kgDM) The energy value of silage is expressed as the amount of energy contained in every kg of silage dry matter as shown in the example above. Young grass will have the highest energy content and mature grass the lowest. The younger and drier the grass the more energy the silage will supply for milk and liveweight gain. Top Quality Average/good Poor quality
