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Grass Conservation - Hay/Silage, high BOD (Biochemical Oxygen Demand), Mr…
Grass Conservation - Hay/Silage
Silage
Controlled Fermentation – reducing the pH (acidity) of the grass to a level where growth of bacteria is inhibited.
Method
Field is closed off to livestock and fertilised 6–8 weeks before cutting.
Grass is mowed at leafy stage before heading out date (Digestibility) (Palatability) (Higher Sugars)
Left to wilt in rows (Swathes) (Increase Sugars)
Lifted by a forage harvester/baler (chops grass) - Allows sugars burst from cell for bacteria
It is rolled by machine to remove air (Anaerobic Conditions)
After rolling, it is sealed with heavy-duty black polythene -> keeps air tight -> allows fermentation
Additives
Molasses: Molasses increases carbohydrate concentration providing extra sugar for the fermentation process.
Enzymes: Enzymes break down grass fibres. This provides additional carbohydrates for fermentation.
Bacterial inoculants: bacterial culture introduced These speed up the fermentation process and reduce pH within the pit. (Maintain Protein)
Bales or Pit
Bales
Advantages
Less dependent on weather
Ideal for surplus grass
Excess bales can be sold
Cheaper for small farmer
No need for effluent storage facilities.
Disadvantages
High unit costs
Labour/time at feeding out
Prone to damage
Plastic waste disposal costs.
Pit Silage
Advantages
Cheaper than bales.
Less Labour intensive.
Easier fed/managed.
Disadvantages
Weather dependent
Effluent storage rquired
Mixing grass qualities.
Heavy Machinery (compaction)
Requires drier soil.
Silage Effluent
by-product
Acidic,
rich in nutrients
appears after about 2-3 weeks
Causes Eutrophication
Eutrophication – Excess nutrients causes rapid plant growth (Removes Oxygen from water killing fish)
Silage Quality
important?
Animal performance (Higher LWG/Milk Yield)
Reducing winter feed costs (Higher Quality = Less Concentrates = Increased Profit)
Higher Production Levels (increasing profitability)
Increases Health and fertility (Animals in better condition)
Indicators of Silage Quality
Dry matter (DM %) The higher the DM, the more energy and protein - Target 25-35%
Crude Protein - Target 12-14% protein
DMD (Dry Matter Digestibility) - How easily digested the dry matter is (Grass) - Target 70%.
Metabolisable Energy - measures the usable energy of the silage - Target 11.5+
Ash - soil or organic manure contamination - Target <10%
pH - 3.8-4.2 well preserved
Hay
Dehydration – removing the level of water to inhibit microbial activity.
Method
Field is closed off to livestock
Fertilised Lightly by Fertiliser
Grass should be cut at midday to increase sugars
Grass is mowed when seed heads are not ripe (Digestibility) (Palatability) (Higher Sugars)
Baled when moisture reaches <20%
Grass is "tedded" out (x2) to dry out grass and left wilt (Increase Sugars)
Storage
Dry – Prevent Moisture and bacterial breakdown
Ventilated – keep hay dry and increase storage time
Cool – Prevent Heating Damage (Fire Hazard)
Advantages
Transportable – Small Square bales
Suitable for all Animals
Relatively cheap – Less Fertiliser
Suitable for all farm sizes
Clean
No Effluent
Disadvantages
Weather Dependent
Feed Value is reduced
High Water requirement when feeding.
Labour Intensive
Adequate Storage Required
The science behind Silage
It's a Biochemical Process (Anaerobic Process)(Involves Bacteria)
Freshly cut grass contains millions of bacteria
Cutting process causes cells to burst, releasing carbohydrates.
The type and number of bacteria depends on the amount of Carbohydrates
How to increase Carbohydrate (Sugars)
Cut grass at Leafy Stage (High Sugars)
Cut in Dry Conditions– wet grass reduces carbohydrate concentration.
Wilt for a period of time after cutting (1 – 2 days) – increases Carbohydrate's.
Cut Grass in Short pieces – makes the crop more accessible to bacterial activity.
Using an additive (e.g. Molasses) - to increase lactic acid production.
Cut in After mid-day – Sugars highest in Afternoon
Compacting the grass, removes oxygen and creates anaerobic conditions
In anaerobic conditions, bacteria present cause fermentation to occur.
Fermentation causes acid to be produced which lowers the pH
Bacterial growth and actions cease.
Grass is now Preserved
Bacteria Involved in Silage Production
High levels of Carbohydrates allow Lactobacillus and Streptococcus to produce Lactic Acid
Sweet Smell
Good Quality
Low levels of carbohydrates allow Clostridium to produce Butyric Acid.
Stinks/Rancid
Poor Quality
Compare Hay & Silage
Silage
Method of preservation
Fermentation - Anaerobic
Lactobacillus Bacteria Convert sugars to Acid
Effluent - 60 Lites/Tonne
DMD - 70-80%
Storage - Storage Bales or Pit:
Sealed with polythene black plastic
Dry Matter - 25%
pH - 3.8-4.2
Cost - 15 Euro Per Bale
Hay
Method of preservation
Dehydration-Aerobic
No Bacteria Involved
Effluent - None
DMD - 65-70%
Storage - Dry,Ventilated,Cool
Dry Matter -80%
pH - 6.0
Cost - 1 – 5 Euro Per Bale
high BOD (Biochemical Oxygen Demand)
BOD = How much Oxygen is needed to break it down.
Mr P Reynolds