Transcript Cost effective dairy cow nutrition

2. Cow nutrient requirements
and ration formulation
ANIM 3028
Tom Cowan
Tropical Dairy Research Centre, UQ, Gatton
1
Sources of nutrients
• All feeds supply one or more
• the primary feeds (pasture, forage, grains,
byproducts) contain all, but in varying
quantities.
• Energy and protein come in various forms
(e.g. starch, fibre and sugar for energy)
(e.g. NPN, amino acid mix for protein)
2
Minerals and vitamins
• Minerals
availability in feed
– associated feeds
– form of mineral
– level of animal
deficiency
• Vitamins not of concern
– Most vitamins or their
precursors are in feeds
– housed cows on dry feed
may need A and/ or D
– Vitamin e (or Se) may
protect against infection
– rumen microbes produce
water soluble vitamins
(B,C)
3
Rumen function
• Cow nutrition is largely rumen fermentation
• Optimising microbial growth
– rumen capacity (L)
– wall papillae
– development of capacity and papillae depend
on level of feeding
– feeds produce VFA (volatile fatty acids - acetic,
propionic, butyric)
– VFA absorbed through wall of rumen (papillae)
– acetic for milk fat/propionic for milk protein
4
Protein absorbtion
• Protein absorbed from intestines
• Mix of feed protein (UDP), and microbial
protein (bacteria and protozoa)
VFA
Feed
Microbial
protein
5
Energy and protein utilisation
• Energy
• Gross energy similar
• Primary variation due
to faeces output
• urine and methane less
variable
• metabolisable energy
used in Australia as
unit
• Protein
• very different levels in
feeds
• two primary sources
of variation in
utilisation
• rumen ammonia and
faeces
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Maintenance and production
• Maintenance = energy to maintain body
• Level of feeding = multiple of maintenance
• Efficiency declines as level of feeding
increases
• For simplicity usually discussed as
maintenance (0.8 efficiency) and production
(0.2 to 0.6 efficiency)
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Cow requirements
• Annual cycle in milk yield, dry matter
intake and live weight
Live
weight
• Lactation curve is the measured cycle DMI
• “normal” curve peaks at 6 to 8 weeks after
calving, and falls at 5% a month thereafter
• “in practice” curves may be all shapes,
Milk
depending on feed supply
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Quantitative requirements
• Over the full lactation milk output is related
to DMI
– 12L milk - 12 kg DMI
– 20L milk - 17 kg DMI
– 30L milk - 23 kg DMI
• Water needs from 20 to 120L/day
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Ration formulation
• Essential tool in feeding cows
• enables the ration to be balanced
• enables the amount of ration to be set
Nutrient
requirements of
cow
Nutrient contents of
feeds
Ration formulation
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Nutrients in feeds
• Need to measure in feeds
• Is not an exact science
• energy - fibre or digestibility analysis to
give ME as MJ/kg DM
• protein - N*6.25, rumen degradability
• minerals - DM/DM
• vitamins - not measured
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Simple ration formulation
E.g.
CSM
40%CP
6
By subtraction,
ignore sign
16
Barley
grain
10%CP
24
Ration needs to be 6/30 CSM and 24/30 barley
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Complex ration formulation
• Computer based
• You choose type - put in the feeds and the
program tells you what is in the diet, then
you decide (needs a good nutritionist)
• Optimisation type - linear program, gives
diet of least cost, highest production, etc.
(needs an excellent program)
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Nutrients and their description
• Energy, Megajoules of metabolosable
energy (MJ ME)
• Protein, kg
• Minerals, g or mg
• Vitamins, International Units
• water, L
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