2. Cow nutrient requirements and ration formulation

1. 2. Cow nutrient requirements and ration formulation ANIM 3028 Tom Cowan Tropical Dairy Research Centre, UQ, Gatton

2. 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)

3. 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) Minerals and vitamins

4. 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

5. Protein absorbtion • Protein absorbed from intestines • Mix of feed protein (UDP), and microbial protein (bacteria and protozoa) VFA Feed Microbial protein

6. 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 Energy and protein utilisation

7. 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)

8. 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 Live weight DMI Milk

9. 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

10. 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

11. 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

12. 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

13. 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)

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