Applied Animal Nutrition-I

Methods of determining digestibilty

METHODS OF DETERMINING DIGESTIBILITY

Digestion trial vs. Metabolism trial

Particulars	Digestion trial	Metabolism trial
Purpose	Gives information on proportion of nutrients in a feed or diet that are absorbed from the gastro intestinal tract	Similar to digestion trials but gives more information on utilization of nutrient after absorption from the gastro intestinal tract
Information obtained	Information on digestibility co-efficient of nutrients	In addition to digestibility co-efficient, one gets information on nutrient balances such as nitrogen, calcium, pPhosphorus, energy etc. Hence, metabolism trials provide complete information on nutrient digestion and utilization from feedstuffs than digestion trials
What is collected	Only feces	In addition to feces, urine, milk, gases like co, sloughed hair, feathers etc are also collected
Result	Apparent digestibility co-efficient of nutrients	In addition to apparent digestibility co-efficient of nutrients, the information on positive or negative nutrient balance is obtained

Methods of Determining Digestibility

I. In vivo method

• In this animals like sheep, goat, rabbit, pig, dairy cattle etc in which digestibility of a feed is to be determined are used.
• The two in vivo methods are :
  • Direct Method or Conventional method
  • Indirect: In the indirect method there are two methods:
    • Difference Method
    • Indicators/Markers Method

II. Semi in vivo methods

• Nylon bag technique 
• VIVAR technique

III. In vitro methods

• Using rumen liquor
• Using enzymes instead of rumen liquor
• RUSITEC method