Animal production (not forage production)

Animal intake = production

• near perfect relationship between intake and quality
• higher efficiency per kg DM with better quality forage
• At 2.5% of bodyweight most livestock are constrained by gut fill,

higher intake (i.e. top-end production) is only possible with high quality forage

Quality determines forage value

Yield is not enough
Maximum yield does not always coincide with maximum quality

Animal breed (cattle vs sheep)

• diet is affected by mouth dimensions - sheep and goats show greater selectivity than cattle
• previous exposure to forages
• metabolic differences - e.g. sheep have an enzyme that allows them to breakdown alkaloids in tansy ragwort, these alkaloids are toxic to cattle

Diet selection - animals will select the better quality components from a mixed pasture

Palatability – an indirect and poor measure of quality, summation of factors affecting animal preference (including taste, smell, texture & familiarity), otherwise nutritious forage may have low palatability

Cell structural components:

1. soluble
2. hemicellulose
3. cellulose
4. lignin

• energy (carbon)
• protein
• minerals
• anti-quality components

Animal - the only true measure of forage quality, integrates all components, expensive and difficult

• performance (growth, production)
• invivo-digestibility

Visual appraisal

• Leafiness
• Color
• Plant staging – observe emergence of the seed head within the pseudo-stem
  

Lab analysis

• Proximate analysis (pg 370)
• Van Soest analysis - ADF & NDF (pg 372)
• NIR – near infa-red reflectance, needs calibration (pg 373)

Relative feed value (pg 374)

• RFV=[(120/NDF)*(88.9-0.779*ADF)]/1.29
• ADF and NDF are correlated, RFV is driven by NDF
• excludes protein
• underestimates the value of grasses compared to legumes