Factors affecting Feed Composition

• Genetics ↔️ environment - chemistry; crude protein, fibre, carbohydrates, plant secondary metabolites.

  Animal ↔️ genetics - chemistry and digestibility; digestible lysine, metabolisable protein, metabolisable energy

  Affects on feedstuff composition

  
• The ratio of crude protein to sugars in different grass species is a negative relationship. As crude protein increases, the sugar stores in the grass decrease.
• Soil pH is a key driver for mineral availability and in turn plant nutrition. Too low of a pH causes stunted growth and a variation in mineral content.
• Management of soil pH:

  • Increase pH: add limestone
  • Decrease pH: add sulphur
• Soil pH management is a balancing act. Nitrogen fertilizing is pH reducing as is regular liming and soil buffering from carbon management.
• Diurnal patterns for non-structural carbohydrate levels are key for efficient harvesting. Carb levels rise during the day, peak late afternoon/early evening, and decline during hours of darkness.
• Growth of plants for animal feed harvesting are affected by six key things:

  1. Soil type e.g. is it sandy, dry, waterlogged? etc.
  2. Soil pH
  3. Light/photosynthetic rate
  4. Plant species
  5. Temperature
  6. Rainfall
• Factors affecting digestibility:

  1. Chemical composition
  2. Nutrients available from the food
  3. Animal Species
  4. Animal health
  5. Animal Age
• The level of feeding in an animal is the amount of food that is ingested over a set amount of time. It is less important for monogastrics but is of high importance for ruminants.
• The link between rumen retention time and feeding level is influenced by various factors. Generally, higher feeding levels can lead to longer retention times due to increased rumen fill and changes in feed particle size and digestibility.
• Enzymes are good at reducing anti-nutritional factors and therefore assisting digestibility.
• Phytase causes phytate degradation to release phosphorous. There are also benefits on availability of other minerals (Calcium) along with improved amino acid digestibility.
• Carbohydrases break down fibre in cell walls with an emphasis on arabinoxylan (reduction in viscosity).
• Protein, fat and starch digestibility are fairly similar between ruminants and monogastrics.