Forage Conservation

• Why consider conservation


  Forage is required all year round

  • seasonal growth - needs to be conserved for winter feeding
  • provision of forage when demand exceeds supply
  • eg horses
  • grassland management tool
  • when grazing av exceeds grazing needs
• Objective of conservation


  Preserve a product with sufficient digestible nutrients

  • high quality preservation is key to:
  • palatability
  • longevity
  • nutritional quality
  • minimising health risks
  • not limited to animal feeds
• Two principal ways


  Removing moisture for aerobic storage

  • dried in field, or barn, or both
  • hay making and artificial dehydration

  acidification in an anaerobic environment

  • fermentation and storage of moist crop
  • silage making
• Hay

  Reduce moisture content to inhibit any microbial enzymes

  • water in crop: 650-850 g/kg
  • water in hay: 150-200 g/kg

  fine weather: grass will dry over time

  • drying enhanced by field treatment
  • expensive alternative: barn drying

  cut later in the season

  • drier but more mature
  • digestibility reduced but hay-making more successful
  • speed of drying impacts nutrient loss
• Hay - drying losses


  Lose plant enzymes that would help with digestion

  • sugars are used up by respiration
  • protein breakdown

  rapid drying to minimise nutrient losses

  • mechanical assistance
  • crush, crimp, roll but minimise shatter
  • shatter reduces nutritional value
  • cell content loss; end product more cell more
  • requires several days to dry
  • at the mercy of the weather
• Hay - challenges 


  Slow drying

  • risk of losing nutritional value

  additional risk of slow drying

  • microorganisms: bacteria and fungi
  • fermentation: acetic and propionic acids
  • mouldy hay: mycotoxins (farmers lung)
• Hay - conservation assistance


  Additives can assist

  • buffered ammonium propionate

  bald at higher moisture levels

  • up to 30% moisture (dry matter (DM) 700 g/kg)
  • normally <15% moisture to prevent moulding

  benefits

  • reduced losses
  • higher nutritional value
  • safe storage
• Hay - storage challenges 


  Changes during storage

  • high dry matter (DM)
  • minimises risk of bacterial fermentation
  • low DM (>15% moisture)
  • risk of excessive bacterial fermentation
  • rise to temperature
  • risk of spontaneous combustion (flames)
  • moulds
  • respirable particles - dust
  • can cause problems, especially for horses
  • if dust is a problem, soak for 30mins
• Silage


  Conserved crop of a high moisture content through controlled fermentation

  • anaerobic conditions are essential
  • chop, rapid fill, consolidate, seal
  • allow for growth of lactic acid bacteria
  • encourage natural growth of lactic acid bacteria
  • discourage activity of undesirable microbes
  • clostridia spp
  • assist through additives to achieve drop in pH
  • encourage lactic acid bacteria
  • chemical additives
• Ensilage - role of enzymes 


  Enzymes help respiration to start which then uses up oxygen and creates anaerobic conditions.

  Proteolysis - water and enzymes break peptide bonds and when pH gets too low, hydrolysis stops which means fermentation starts
• Ensilage - role of bacteria


  Bacteria is necessary for desirable (primary) fermentation to create silage. Necessary to stop breakdown of proteins and build up of ammonia-nitrate. Having bacteria decreases level of butyric acid in silage.
• Ensilage - role of bacteria 


  Undesirable (secondary) fermentation builds up ammonia-nitrate and produces butyric acid and allows clostridia bacteria to contaminate the silage
• Key priorities in silage making 


  Cut crops at their optimum stage of growth

  • achieve minimum DM of 250 g/kg
  • chop to correct length

  eliminate soil contamination at all stages

  fill silo or clamp by method that prevents air movement, oxidation and heating

  • consolidate by rolling to expel trapped air

  completely seal against entry of air as soon as filling is completed

  • big bales - wrap well, stack and store carefully
• High temperature dried forage


  Grass or lucerne is cut at an early growth stage, wilt, chop, dry and cool. Exposed to very high temperature 500-1000 degrees Celsius for 30secs-2mins which is efficient but very expensive. Reduces time from drying, maintains nutritional value and digestibility, high levels of metabolisable energy and crude protein.
• High temperature dried forages


  Used in specialist markets; rabbit, guinea pig and horse food. Some in concentrates for layer diets in chickens to increase quality of eggs. Misleading fibre levels, high levels of neutral detergent fibre analysed to typically be >50%. Analytical fibre is not functional fibre and for this method of drying, there is no longer a fibre source for chewing and rumination.
• Straw

  Lower quality compared to hay, has to be dried a little longer so it loses most of its nutritional value. Sometimes ammonium propionate is added to improve the conservation. Used in grazing animals as source of fibre but for high producing animals you can’t rely just on straw. Little nutritional value unless molasses or pot-ale syrup is added.
• Overview of nutritional values

  
• Ammonia treated straw 


  Direct application of ammonia

  • 35kg ammonia per tonne of straw DM

  nutritional value

  • Metabolisable energy 7.7 MJ/kg DM
  • crude protein 80 g/kg DM

  spring calves

  • add ammonia to straw but minerals and vitamins are still needed for good nutrient supply in animal

  reduce the need to add concentrate as animal is already satisfied with crude protein requirement but mineral and vitamin supplements are still needed.
• Urea treated straw 


  Ammonia is formed from action of urea to improve protein content in the straw. Increase level of production of ammonia by improving bacteria which is the break down of urease and production of urea.

  Outcomes

  • preserve moist straw
  • increase nitrogen content
  • increase crude protein content, not true protein
  • variable effects on digestibility
• Other technologies 


  “Traditional” conservation

  • forages

  other conservation techniques

  • cereals

  cereal conservation

  • addition of alkaline, caustic or urea
  • choice depends on moisture level when harvested

  key characteristics

  • conserve at high pH which is beneficial for rumen health
  • reduction in (sub-clinical) acidosis risk

  alternative

  • use of propionic acid
  • conserve at low pH without relying on fermentation