Norms adopted in conducting digestion and metabolism trial


Selection of animals

  • The animals should be of the same breed, sex, age and body weight.
  • Generally a minimum of four adult animals are needed.
  • Animals should be healthy and free from parasites.
  • Male animals are preferred to females because it is easier to collect faeces and urine separately.

Preliminary Period

  • The test feed has to be fed daily in constant amounts, as per the requirements of the animal, for an extended period. This is called preliminary period.
  • The purpose is to make the gastrointestinal tract free of any indigestible material from the feed consumed prior to the start of the digestion trial.
  • In monogastric animals such as pigs, digestion and evacuation are usually complete in 24 hours after the test feed is ingested.
  • In ruminants eating a roughage ration, the last residues may not be voided until 150 to 200 hours (6 to 8 days) have elapsed, though 95% are usually voided  within 140 hours. So preliminary period of 2 - 3 days (some times 3 - 5 days) in pigs and 7 - 14 days (8 - 10 days) in ruminants is followed to eliminate the feed residues of previous rations from the digestive tract and to stabilize the daily feed intake and faecal output to a constant level.
  • Water and salt licks are provided at all times.
  • Animals are fed individually

Collection period

  • Animals are transferred to cages or stalls and a 2 - 3 day adaptation period is allowed for their acclimatisation. This follows collection period of 7-10 days duration; A 5-7 day collection period is mostly followed.
  • In general, the longer the period of collection the more accurate the results are, provided the stated amount of feed continues to be consumed regularly and completely, since the effect of periodic fluctuations is minimised.
  • Quantitative collection of faeces and urine are done.
  • Representative samples of feed offered, feed leftovers and faeces and urine voided are  preserved and analysed for nutrient composition.

Test feed

  • The test feed should not be deficient in the nutrients because a deficiency of some of them may affect digestion process.
  • The test feed should be fed at the level required for meeting the requirements of the animals.
  • Normally 90% of the actual feed intake, as measured during the previous week, is offered.
  • Direct determination of digestibility of individual feed may be done if it provides a satisfactory ration for the test period when fed alone.Some feeds cannot be fed alone as they do not supply the bulk and therefore their digestibility coefficients cannot be determined, cereal grains, concentrate mixtures. Similarly, non -maintenance type of roughages like straw, stovers, dried grasses, etc. do not supply the required  amounts of nutrients and so they cannot be fed alone to the experimental animals.
  • In the above mentioned cases digestibility is measured by indirect methods.
Last modified: Wednesday, 4 April 2012, 5:18 AM