Meeting the Cows Needs

Understanding the analysis
• The first step is to identify the cows’ allowances for energy, protein, fibre and minerals based on bodyweight and yield.

• The next step is to determine the supply of nutrients from the feeds and supplements the cows are getting

• The difference between these two is the gap which needs to be filled. The mineral/trace element gap should be filled.

ME – MJ per kgDM

  • Me – Metabolisable Energy 
  • ME is defined as the Gross Energy (GE) of the feed less that of the faeces, urine and combustible gasses (methane) 
  • Feed energy is typically reported as metabolizable energy (ME). ME is a calculation derived from digestibility.  There is no physical ME component in feed. 
  • Energy is required for al bodily functions. Energy mainly derives from carbohydrates (sugars, starches) and lipids (fats, oils), but also from protein. 
  • A ruminant doesn’t directly take up most of the sugars/starches in feed. 
  • Much of the ingested sugars and starches in feed eaten by the ruminant is utilised by the rumen microbes, rather than directly by the animal.

 ME – volatile fatty acids 

  • In the process, rumen microbes produce substances (volatile fatty acids – VFA) that are needed by the animal an are absorbed mostly through the rumen wall. 
  • These substances are energy precursors for the ruminant and are used to produce glucose and fats. Thus, rumen microbial activity meets much of the ruminant’s energy needs up to 70%.

 CP – Crude Protein 

  • Crude Protein – is estimated chemically by measuring nitrogen and is then multiplied by 6.25 to give us crude protein 
  • Crude Protein – is NOT true protein, true protein is made up of building blocks all amino acids. 
  • Effective Rumen Degradable Protein (ERDP) is the amount of dietary nitrogen (protein) which is broken down in the rumen and converted to rumen microbial protein. 
  • Microbial Protein (MP) is a better term to describe protein. 
  • DUP (bypass protein) – is the fraction of feed which has not been degraded during its passage through the rumen which is digested in the lower intestines 
  • Diets high in oil provide less rumen energy and reduce microbial protein production. 
  • DUP + MP gives us Metabolisable Protein. 

Excess Nitrogen 

  • Over feeding of nitrogen (N) – excess N enters the blood stream as ammonia (as a toxic molecule) which is then converted to urea (not-toxic molecule) by the liver and excreted (urine) by the kidneys.  This process costs energy !! 


  • Starch – is made from sugar units built in a complex 3-dimensional structure 
  • This complex structure can be opened up by heat and moisture 
  • Starch that have been heat treated are easier for the rumen to breakdown and ferment 
  • Starches from wheat and barley are fermented rapidly, and can cause rumen problems such as acidosis (fall in rumen Ph) 
  • Starch that is quickly fermented provides energy to the rumen microbes (Rumen Starch) 
  • Starch that is slowly fermented may be washed out of the rumen without being broken down by the rumen microbes provides energy to animal directly,. 


  • Sugars are carbohydrates consisting of 1 or 2 units of glucose, fructose or other simple forms. 
  • Quickly degraded in the rumen and provide an excellent source of energy. 
  • Unlike starch, sugars don’t appear to lower rumen pH 
  • Recent research work has shown that sugars increase the yield of microbial protein 

Fats and Oils 

  • Dietary fat is a wider term which covers various feeds with mixtures of oil or free fatty acids 
  • Different oil sources have different effects 
  • Unsaturated fats (soya, canola, fish oil) can interfere with fibre digestion 
  • Saturated fats (e.g. Palm Oil) have less of an effect with fibre digestion. 
  • Dietary oil tends to enhance milk fat % and reduce milk protein %. 

FME – Fermentable Metabolisable Energy 

  • FME is the ME content of the feed or diet less the ME present as total oils and fats 
  • Dietary fats and oils, whilst highly digestible in the ruminant digestive tract cannot supply molecules of energy to the rumen microbes. 

4% oil – reduces FME by 1.4Mj/kgDM

 Priority of Decision Making 

  1. Energy – amount, source

  2.  Protein – rumen RDP, by-pass UDP

  3.  Effective Fibre – structure

  4.  Mineral & Vitamins – (re)production, health

  5.  Other Factors  -  interactions, stress


Maximise Sustainable Production 

Optimise Inputs vs Outputs

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