2 Cow nutrient requirements and ration formulation ANIM

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 6

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) 7

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 8

Quantitative requirements • Over the full lactation milk output is related to DMI – 12 L milk - 12 kg DMI – 20 L milk - 17 kg DMI – 30 L milk - 23 kg DMI • Water needs from 20 to 120 L/day 9

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 10

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 11

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 12

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) 13

Nutrients and their description • Energy, Megajoules of metabolosable energy (MJ ME) • Protein, kg • Minerals, g or mg • Vitamins, International Units • water, L 14