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.
- 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
- Energy – amount, source
- Protein – rumen RDP, by-pass UDP
- Effective Fibre – structure
- Mineral & Vitamins – (re)production, health
- Other Factors - interactions, stress
Maximise Sustainable Production
Optimise Inputs vs Outputs