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2. Cow nutrient requirements and ration formulation

ANIM 3028Tom Cowan

Tropical Dairy Research Centre, UQ, Gatton

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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)

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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)

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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

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Protein absorbtion

• Protein absorbed from intestines

• Mix of feed protein (UDP), and microbial protein (bacteria and protozoa)

FeedMicrobial protein

VFA

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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

• Lactation curve is the measured cycle

• “normal” curve peaks at 6 to 8 weeks after calving, and falls at 5% a month thereafter

• “in practice” curves may be all shapes, depending on feed supply Milk

Live weight

DMI

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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

Barley grain 10%CP

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6

24

By subtraction, ignore sign

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