Management involved in making quality silage

Basim Refat

OutlineFirst part- Introduction - Advantages and disadvantages of different silo types

Second partImportance of excluding air in silos1. Packing2. covering

Introduction

• Storage losses during ensiling process:• type of silo• species, stage of maturity• moisture content of the ensiled crop • the efficiency of excluding air and water from the silage.

• This feed loss is made up of the following:

• Surface Spoilage

• Ensiling Losses

• Seepage losses

SILOproper

environment for ensiling

Exclusion of air from the ensiling mass

Reducing feed loss

There are several ensilinge methods that will

accomplish the ensiling process

All methods have advantages and disadvantages,

and have widely ranging capital costs. 

1. Vertical Silos(a) open to the atmosphere on top i.e. open- top; or (b) (b) sealed to control the internal atmosphere - i.e. - oxygen-limiting.

2-Horizontal Silos • There are two types of horizontal silos –

• Below ground level (i.e., pit or trench) • Above ground

• Bunker • Pile or stack or heap or clamp• Plastic silage bags• baled silage

The main advantage of horizontal silos is their low capital cost

and suitability to feeding livestock in widely separated pens. 

Vertical silos

built of either concrete or steel

• open to the atmosphere on top i.e. open- top; or

• sealed to control the internal atmosphere - i.e. - oxygen-limiting

Horizontal silos

1. Below ground level (i.e., pit or trench) • Trench silos are usually dug into a slope with the "downhill" end open for

drainage and access.

2- Aboveground horizontal silos

• Stack Silage; (Pile) Stack

• Silage Bunker

• Silage Bag

• Baled Silage

DM filling Seepage Gaseous top surface feed out total---------------------------DM Loss (%) ------------------------------

conventional tower

80 1-2 7 9 3 1-5 21-2670 1-2 1 8 4 1-5 15-2065 1-3 0 8 3 1-5 13-1960 1-3 0 6 3 1-5 11-1750 2-4 0 5 3 1-5 11-17

Gas-tight tower

70 0-1 1 7 0 0-3 8-1260 1-2 0 5 0 0-3 6-1150 2-3 0 4 0 0-3 6-1240 2-4 0 4 0 0-3 6-13

Dry matter loss for filling, storage and emptying a variety of silage storages

Based on Forages: The Science of Grassland Agriculture, 4th ed. See Bickert et al (1997).

---------------------------DM Loss (%) -----------------------------trench or bunker

no cover 

80 2-5 6 10 6 3-10 27-37

70 2-5 1 9 9 3-10 24-34

60 3-6 0 10 12 5-15 30-43

trench or bunkercover

 

80 2-5 4 9 2 3-10 20-30

70 2-5 1 7 3 3-10 16-23

60 3-6 0 6 4 5-15 18-31

Stack, no cover

80 3-6 7 10 11 3-10 34-44

70 3-6 1 11 19 3-10 37-47

60 4-7 0 12 24 5-15 45-58

Stack, covered

80 3-6 5 8 2 3-10 21-31

70 3-6 0 7 4 3-10 17-27

60 4-7 0 6 6 5-15 21-34

Wrapped Silagebales

60-70 1-2 0 8 5 1-5 15-20

50-60 2-3 0 6 6 1-5 15-20

DM fillingSeepa

geGaseo

ustop

surfacefeed out

total

Based on Forages: The Science of Grassland Agriculture, 4th ed. See Bickert et al (1997).

Effect of storage systems on composition alfalfa silage

Bunker O2-Limiting Tower p- valueDM, 36.8b 54.0a 49.6a <0.001CP,% of DM 19.4 20.7 19.7 0.305NPN, % of Total N 62.3a 55.4b 55.0b 0.014NH3, % of Total N 13.11a 6.79b 7.14b 0.008Total AA, % of Total N 32.3 32.2 33.3 0.269ADF,% of DM 40.5a 34.9b 35.9b <0.001NDF,% of DM 45.8a 41.5b 41.8b 0.02Lactate 3.67ab 2.86b 4.42a 0.028Acetate 2.87a 1.16b 1.46b <0.001pH 4.84 4.87 4.69 0.34

Luchini et al., 1997

Advantage and disadvantages

• Silo tower• Have a smaller surface area exposed to the elements and therefore less

spoilage than horizontal silos

• Horizontal tower • Horizontal silos generally cost less per stored ton than upright silos • more adaptable to mobile mixing and feeding systems than vertical silos.• They can be filled and emptied with conventional farm equipment and

require less energy to move the forage• Tend to have the greatest losses of dry matter

• Drive-over piles • require low capital investment relative to bunkers• piles may be constructed with conventional farm equipment, and

fast unloading rates.

• Plastic bags • low capital investment • flexible storage system (qualities and types)• low DM loss if properly managed, • small feed out face to manage• Easy to feed out

• The stack system • greatest loss of dry matter during storage, (30-35% ) of the total forage

harvested. • large amount of surface area exposed to the air • the stack cannot be packed as densely to exclude oxygen.

• not recommended for long-term storage.

• Bales • Susceptible to aerobic deterioration owing to their relatively high ratio of

(surface area: volume)• Chop length typically is longer and density lower for baled crops than for

forage-harvested crops

(Wilkinson, 2005).

Silage Bag

• Plastic bags are not reusable

• DM loss can be high if bags are ripped or torn

• specialized equipment is necessary,

• more land area than bunkers or piles,

• small feed out face may be difficult to manage on large dairies feeding high volumes of silage

Importance of excluding air in silos

• Packing

• Covering

Packing

Packing

Density

DM concentration

permeabilityAerobic Deterioration

during

Storage

1- Density

• Density and dry matter content determine the porosity of the silage

• Porosity, in turn, sets the rate at which air moves into the silo • subsequently the amount of spoilage which occurs during storage and

feed-out.

• The higher the density, the greater the capacity of the silo. • thus, Higher densities generally reduce the annual cost of storage per

ton of crop by both increasing the amount of crop entering the silo and reducing losses during storage.

• Tractor weight and packing time are the most important factors affecting density. Ruppel et al. (1995)

Estimated Dry Matter Density (Est.DMD)

• Est. DMD (lbs DM/ft3 ) = (8.5 + PF × 0.0155) × (0.818 + 0.0136 × D) • (D) average depth • (PF) packing factor are calculated as:

• D = average silage depth (ft) = (height at wall + height at center) / 2.

• PF = (• W = Proportioned average tractor weight (lbs) for all tractors packing silage.• L = Layer thickness (inches) of the spread but unpacked crop in the silo prior to driving over it

during the first packing pass.• N = Number of tractor-packing equivalents, w• DM = Dry matter content (decimal).

Holmes, 1999

Effect of density on silage aerobic stability:

The relationship was influenced by DM concentration

• DM loss decreased with increasing DM concentration at higher DM densities (more than 240 kg DM m−3)

• Lower DM densities (<210 kg DM m−3), DM loss increased markedly at higher silage DM concentrations (350–390 kg DM kg FW−1).

(Griswold et al., 2009)

• Silage density varied within the silo in which is low top thirds and high in middle and bottom thirds.

• Density is typically lower at the edges of walled bunkers and unwalled clamps

• The DM density in 113 silos filled with whole-crop maize was on average 8% lower close to the outer walls than in the centre of the silage mass

(Craig et al., 2009)

Effect of density on silage aerobic stability

•Fill quickly (no more than 3 days)

•Pack tightly

• Corn silage : (240 kg DM/m3)

• Alfalfa silage: (255 kg DM/m3)

• Grass silage: (210 kg DM/m3)

•6-8 inch (15-20 cm) layers

•Heavy tractors

Holmes and Muck, 2007

Adesogan, 2009

Kung, 2010

Recommendation

2- Silage permeability and porosity

• Porosity is a measure of the voids between the solid particles

• Proportional porosity (ø) can then be calculated as:ø = 1 − (ρ/ρmax)

• ρ = silage FW density (kg m−3) • ρmax = maximum silage FW density when all voids are removed. • (ρmax, kg m−3) = ρmax = [3/(3 − DM)]×1000.

Silage porosity is influenced

• FW density,

• the DM content of the crop

• by rate of harvest

(Wilkinson and Davies 2012)

Silage permeability and porosity; Density &DM

• Porosity ranges from 0.1 for silage of • 300 g DM kg−1 FW• 1000 kg m−3 FW density

0.7 for silage of• 700 g DM kg−1 FW• 400 kg m−3 FW density

(Holmes and Bolsen, 2009)

Silage permeability and porosity; Harvest rate

Harvest rate

DM content

porosity

Holmes and Muck (2007)

Covering

Losses of DM in pit silages stored either unsealed or sealed

Film cover

• The quantity of film applied to bales, usually expressed as number of layers, and has marked effect on the loss of silage production and subsequently the subject of evaluation.

• For example using 8 layers instead 6 reduced the mold production significantly

• So by increasing the number of layer the production of mold would decrease.

(Jacobosson, 2002).

Effect of bale density and number of layers of plastic film on the quality of baled silage

Adapted from O’Kiley et al (2000)

The effect of film colour on silage compostion and mould growth

Forristal et al. 1999

White plastic is preferable, due to its superior UV

resistance, reduced silage temperatures beneath it, and

reduced freezing problems during winter. 

Countries with high sunshine level generally use white

or light-colored film which reduce film temperature and

heat transfer.

Covering silage

• Polyethylene cover• weighted with truck tires,•  the protection provided is highly variable and often changes during storage

• Oxygen barrier film (OB film) • Alternative to polyethylene seal• 45µm in thickness, • Increase the preservation efficiency and nutritional quality of silage within 0.5

to 1.0 m of the surface in bunker silos and drive-over piles.

Correlation between the permeability of a film to oxygen and silage quality

• DM losses due to LD-PE film permeability in relation to film thickness • losses from 24.4 to 3.2 g kg−1 DM per 30 day period of conservation for film

thicknesses that increased from 25 to 200 µm.

• Oxygen barrier polymers + LD-PE, allow oxygen impermeability to be increased to values that can only be achieved by LD-PE films that are thicker than 2000 µm.

Borreani et al. (2013)

Oxygen barrier film (OB film) VS Conventional film

Orosz et al. (2012)

Temperature changes of maize silages during exposure to air

Oxygen barrier film (OB film) VS Conventional film

Economics of sealing corn silage in bunker silos with standard (Std) plastic and OB film

Variables Std plastic OB film Silage value. $/tonne 44 44Silage density in top 0.9 m. kg/m3 624 624Silage density below top 0.9 m. kg/m3 768 768Silo depth. m 3.66 3.66Silo width. m 12.2 12.2Silo length. m 45.7 45.7Silage lost in the original top 0.9 m:unsealed. % of the crop ensiled 50 50sealed. % of the crop ensiled 20 10Cost of covering sheet, ¢/m2 50 140Silage in the original top 0.9 m. tonnes $313 $313Value of silage in original top 0.9 m. $ $13778 $13778Value of silage below original top 0.9 m. $ $52000 $52000Value of silage lost if unsealed. $ $6889 $6889Value of silage lost if sealed. $ $2755 $1378Sealing cost. $ $937 $1387Net value of silage saved by sealing. $ $3196 $4124

1Values are from the data by Bolsen et al. (1993) and Berger and Bolsen (2006).