Measurement of digestibility co-efficient

MEASUREMENT OF DIGESTIBILITY CO-EFFICIENT

  • The potential value of a food for supplying a particular nutrient can be determined by chemical analysis, but the actual value of food to the animal can be arrived at only after making allowances for the inevitable losses that occur during digestion, absorption and metabolism.
  • The first tax imposed on a food is that represented by the part of it which is not absorbed and is excreted in the faeces.
  • The digestibility of a food is most accurately defined as that proportion which is not excreted in the faeces and which is, therefore assumed to be absorbed by the animal.
  • It is commonly expressed in terms of dry matter and as a coefficient or percentage. When the digestibility is expressed in percentage it is known as digestibility coefficient.

Formula

  • For example, if a cow ate 10 kg of hay containing 9 kg of dry matter and excreted 4 kg of dry matter in its faeces, the digestibility of the hay dry matter would be:

image 

  • The digestibility coefficient determined is apparent, since the faeces/dung contain metabolic (mucosal debris, unspent enzymes, undigested microorganisms) as well as undigested feed.
  • Dung (digested DM excreted)  = 3.7 kg from feed  + 0.3 kg from body.

image

Formula

Formula

  • Thus the apparent digestibility of feed is less than the true digestibility.
  • The losses of the ingested carbohydrates as methane and carbon dioxide are also accounted in digestibility. So digestibility of carbohydrates is overestimated.
  • Digestibility coefficients are estimated for all organic nutrients. 
  • For ash or minerals it is not estimated, because it does not contribute to energy to the feed, and most of the absorbed minerals are excreted through the gut.
  • In a digestion trial the faecal matter is only analysed,whereas in a metabolism trial both faecal matter and urine will be analysed for losses of nutrients of dietary origin.
Last modified: Friday, 30 March 2012, 9:47 AM