6. Forage Flashcards
Grass varieties
-perennial ryegrass
-italian ryegrass
-cocksfoot, meadow fescue, brome grass, timothy, bent grass, meadowgrasses
-clover
Grassland reseeding
-perennial ryegrass 70%
-italian ryegrass 19%
-cocksfoot 4%
-timothy 7%
Differences between new and old pasture
old pastures have lower yield and digestibility
Aim of grassland management
-provide supply of high quality herbage over the growing season
-avoid waste
-avoid inefficient utilisation by animal
-provide feeding for winter
Grazing behaviour
cattle graze 6-11 hours per day
intense periods after dawn and before dusk
animals move while grazing -slowly in uniform crop and faster in variable crop
grazing followed by rest and rumination
can walk 2-6km/day grazing
drink 2-4 times a day
milking enter/exit field 4 times a day
Factors affecting intake of herbage
Animal factors:
-metabolic weight,
-production,
-stage of lactation
Sward factors
-herbage quantity
-herbage quality
Effort of grazing
-difficult conditions
Effect of animal on pasture
Botanical changes
-frequent grazing, ryegrass
-lax grazing, cocksfoot
-severe grazing, meadowgrasses
Treading and poaching
-compaction more severe when soil wet
-depends on stocking rate, rainfall
Dung and urine
-faeces production
-sheep faeces more evenly distributed
-urine, plant nutrients readily available
Application of slurry
-allow 5 weeks from application to grazing
-contains NPK
Full return of faeces and urine increases herbage yield by 20-40%
Grazing Practices
Continuous stocking
-access to one area for entire grazing season
-balance number of stock with production
Intensive continuous stocking
-reduce number as grass supply drops
Rotational grazing
-divide into number of similar sized paddocks, stock moved in sequence around
Strip grazing
-move electric fence everyday or every 12 hours
-rotation cycle is 15-21-30 days
Leader-follower rotational grazing
-two groups, one follows other
-better use of grass, less waste
Integrated grazing and conservation
-subdivide pasture into 2 sections in ratio of 60:40
-early season graze 40 conserve 60
-mid graze 60 conserve 40
-end season graze 100
Alternate cutting and grazing
-graze part cut early season in mid season and vice-versa
-improves grass quality
-can have shortage of grass for a few weeks
Zero grazing
-harvest all grass and feed as silage
Animal problems at pasture
bloat
parasites
mineral deficiency/toxicity
Bloat
-common with diets high in legumes, lucerne, clover
-problem with lush grass
-control: anti-foam in water, provide some fibrous feed, feed small quantities of pasture with high clover
Haymaking
Reduce moisture content of forage to 20% or less
-suppress fungal growth
-suppress thermophilic bacteria
-suppress moulds
Weather most important
-drying conditions and low humidity
Rapid drying required - mature crop
Harvest 1 June to August
Mature herbage dries easier and quicker, but quality of hay poorer
Forage
mainly grasses, for both domestic and wild animals
Effect of rain on hay quality
Increases moisture content
-prolongs enzyme actions
-increases tossing required
-increases leaching
Encourages mould growth
Nutrient losses during haymaking
Plant enzymes
-respiration CHO to CO2 and H2O
-proteolysis, proteins to amino acids
Oxidation
-carotene destroyed
Mechanical damage
-leaf loss as leaf dries faster than stem
Leaching
-loss of soluble sugars
-loss of amino acids and other soluble nitrogenous constituents
-most caused by rain while saving hay
Silage
controlled fermentation of crop at high moisture content
fermentation produces organic acids from bacterial action on sugars
quantity of acid produced proportional to
-amount of sugar
-type of bacteria
-type of crop
-moisture content
two fermentation types
-aerobic
-anaerobic
Aerobic Fermentation
air trapped in crop when ensiled
respiration proceeds until oxygen depleted
CHO + O2 = CO2 + Heat
loss of carbohydrate
limited loss unavoidable
If extra air enters the silage
-sugar loss by respiration
-increased temperature
-if greater than 40C increased protein denaturation
Decreased digestibility and feed value of silage
Anaerobic fermentation
in absence of air anaerobic microbes produce acid and preserve the crop
Type and quantity of acid critical
-lactic acid desirable
-insufficient acid, clostridia produce butyric acid - protein breakdown, poor fermentation
Relationship between acid type and silage quality
when lactic acid high, butyric acid ammonia nitrogen and pH is low
Moisture content of silage
Low DM herbage (<18%)
–needs high level of acidity to check clostridial growth
Dryer herbage (25-28% DM)
–pH 4.4 adequate
High DM herbage
–initial fermentation to pH 4.8 adequate but fermentation limited
–free sugars remain
–growth of M/O on opening pit
–aerobic deterioration
Soluble carbohydrate content of silage
Depends on
–grass species
–weather
–nitrogen fertilizer
–time of N application
Herbage sugar level of 3% in fresh grass necessary to ensure successful preservation of silage
–wilting
–silage additives
Wilting to improve preservation
Decreases effluent
Increases dry matter
–increases relative sugar content
–less water to transport
–higher field losses
26% DM normally results in good preservation
Dry windy weather, 1% increase in DM/hr
Typical dull weather, 0.4% increase in DM/hr
Additives to improve preservation
Affect sugar content or pH directly
May protect proteins
May improve animal performance
use in difficult crop and difficult conditions
–grass variety –dull wet weather
–young leafy –late regrowth
–well fertilised –soil contamination
–low sugar
Value of silage as a feed
quality, energy and protein content
amount animal east, taste small etc.
On-farm assessment of silage quality
variable layers in pit?
DM content, squeeze in hand
-juice in stream, DM less than 20%
-juice drops only, DM 25 -26%
-wetness on palm, DM 26-30%
ME value, leafiness, coarseness of stem
Type of fermentation
-well fermented, yellow green and fruity smell
-butyric silage, green brown dull and unpleasant smell
-overheated silage, brown black, small of caramel, charred
pH, check with lithmus paper
Moulds
Aspergillus sp. linked to abortion in cattle and sheep
linked to COPD horses from mouldy hay
Listeriosis
Disease of cattle and sheep sometimes linked to feeding incompletely sealed big bale silage
Listeria monocytogenes soil borne, associated with aerobic deterioration
Stemmy silage, iritis
Botulism
Contamination by dead carcasses, soil, manure
Clostridium botulinum may multiply in silage
High ammonia levels
associated with lameness and scour in dairy cows
inverse relationship between dry matter content of silage and lameness
