Ruminant Nutrition III Flashcards
The rumen
In adult sheep = 10-15 litres • In adult cattle = 150-200 litres • Contains 850 to 930 g/kg water • In cattle, usually a caudal mat of fibre • Each mL contains: • 109 to 1010 bacteria • 106 protozoa • 103 to 105 fungi • There are as many bacteria in 1 mL of rumen fluid as people on the planet!
Cattle and sheep cannot digest forages!
2 evolutionary advantages of the rumen
a) Bacteria & fungi can enzymically break down β-glycosidic linkages in fibre
Fermentation of sugars, starch and fibre in the rumen produce short chain, “volatile” fatty acids (acetate, propionate and butyrate)
b) Rumen bacteria utilise ammonia as their N source and do not require pre-formed amino acids in the diet
Urea can be re-cycled to the rumen via saliva or the rumen epithelium, or excreted in urine
Forages
- Grass
- Grass silage
- Maize silage
- Whole crop wheat
- Hay
- Straw
Concentrates
:
• Cereals(barley,wheat,oats) • By-products(sugarbeetpulp,
soya hulls)
• Protein(soyabeanmeal, rapeseed meal)
• Minerals/vitamins
All of the above can be ground and mixed and pelleted to form a concentrate pellet (or cake)
Dry matter (DM) content of forages
- Dry matter: ALL ruminant nutrition is undertaken on a dry matter (DM) basis
- Large variation in the DM content of ruminant forages e.g.
• 20kg of grass silage to a growing beef cow @200g DM/kg=4kgDM • 20kg of grass silage to a growing beef cow @300gDM/kg=6kgDM
Crude protein content of forages
s
• Crude protein (CP): Nitrogen x 6.25
• For grass/grass silage, large range due to stage of maturity
- Less of a range in CP for maize silage/whole crop cereals
- Legume forages (e.g. red clover or lucerne) are higher (mean of 180-220 g CP/kg DM)
Fibre content of forages
- Fibre is measured as neutral detergent fibre (NDF)
- NDF = cellulose + hemicellulose + lignin
NDF content does not indicate how lignified the fibre is
• Dicotylendous plants (e.g. sugar beet) have less lignin in the fibre than monocotylendous plants (e.g. grasses, cereals)
Metabolisable energy content
- ME = metabolisable energy (Megajoules/kg DM)
- ME = gross energy – faecal energy – urinary energy – methane energy
• Animal requirements calculated on an ME basis (e.g. dry dairy cow = 90 MJ/d)
Grazing systems
• Grass growth is not even during the year • Measurement of grass quantity and budgeting • Systems: Set-stocking Rotational Strip grazing Zero grazing (or cut and carry) Out-wintering sheep and cattle
Health issues with grazing
- Bloat (primal ruminal tympany: especially if pasture clover content is high)
- Nitrate poisoning
- Intestinal parasites (“clean grazing”)
- Liver fluke
- Listeriosis
- Clostridial diseases
- Mineral deficiency: (e.g. magnesium (staggers/tetany); calcium (hypocalcaemia: milk fever); copper (swayback); cobalt (pine)
Main methods of feed preservation
- Drying
- Ensiling
- Alkaline treatment
- Crimping
Drying: Hay and barn dried
Made from variety of grasses e.g. ryegrass, timothy, brome,
fescue, or with clovers
• Grass left to become mature (stemmier and higher in NDF than grass)
• Cut and left to air dry in the field for 4-5 days, turning occasionally (depending on weather)
• Baled (round or square bales) at around 850 g DM/kg
• Grass can also be artificial dried and then pelleted
Health issues with hay
• Spontaneous combustion
• Moulds such as fescue poisoning in tall fescue grass caused
by an endophyte fungus (Neotyphodium coenophialum)
• Affects ears, tail and cause lameness and reduced
performance in cattle and sheep
• Mould spores resulting in bovine allergic pneumonitis (Farmer’s lung)
• Botulism (Clostridium botulinum) associated with dead birds or rodents in the hay bale) or if pasture fertilised with chicken litter
Ensiling
• Dairy farms may take 3 or 4 cuts, but upland beef/sheep only one
• Mower is usually a mower-conditioner, and wilted for 24-36 h
• Grass is either direct cut, double chopped or precision chopped
• Can be chopped by self-propelled or trailed chopper, forage wagon or some round balers
• Additives can be used to improve fermentation Bacteria
Enzymes
Stimulants (e.g. molasses) Acids (e.g. sulphuric)
• Storage can be in a clamp, tower or bale (round or square)
• Excluding air, compaction and sealing are very important
• Sugars are fermented into acids (mainly lactic) which reduces
pH
• Series of bacteria involved covering the range of pH 7.0 to pH
4.0
• Lactobacillus spp. dominate at lower pH’s
• If pH drop is not rapid enough, secondary fermentation can
occur e.g. Clostridium butyricum producing butyric acid
• Extent of fermentation (lactic acid production and pH) is less at higher forage DM content at ensiling
Health issues with ensiling
- Aerobic spoilage at feed out and growth of yeasts and moulds
- Mycotoxins e.g. Penicillium, fusarium, reducing performance, milk test failure, abortion, immunosuppression
- Listeriosis (especially in higher DM big bales with a pH above pH 5.4)
- Botulism (if dead animals ensiled)
- Traumatic reticulitis (e.g. wires)
Other methods of preservation
Forages:
• Urea treatment of forage at ensiling (Alkalage) Grains:
• Dry to 14% moisture
• Acid preservation of grains (e.g. propcorn)
• Crimping of moist grains and treatment with acids
• Sodium hydroxide treatment (caustic grain)
• Urea treatment of grains
