nutrient analysis slides

Question 1

Know the advantages and limitations of precision fed rooster assay vs ileal digestibility assay for broilers

Answer 1

1. Precision-Fed Rooster Assay

(Apparent)

• Developed by I.R. Sibbald (1979)
• Method

– Adult cockerels fasted 24-48 hours

– Defined amount of test ingredient (usually 30-35 grams) fed via crop intubation

– Excreta collected assuming all undigested

components have been excreted

Question 2

Know the advantages and limitations of precision fed rooster assay vs ileal digestibility assay for broilers

Answer 2

Advantages of a Precision Fed Rooster

Assay

• Relatively fast
• Inexpensive and requires little labor
• Avoids palatability issues
• Roosters may be used for more than one assay

Question 3

Know the advantages and limitations of precision fed rooster assay vs ileal digestibility assay for broilers

Answer 3

Limitations of the Precision-Fed

Rooster Assay

• Excreta contains both urine and feces

– Metabolizability vs. digestibility

• Hindgut modification by the ceca

– Caecectomy

• Compromises “normal” feeding behavior

– Fasting

– Diet consists only of defined amount of test ingredient

Question 4

Know the advantages and limitations of precision fed rooster assay vs ileal digestibility assay for broilers

Answer 4

Limitations of the Precision-Fed

Rooster Assay

• Ignores correction for endogenous losses

– Endogenous losses: Amino acids supplied to the gut via endogenous secretion.

– Basal endogenous losses: Related to dry matter intake and independent of diet composition.

– Specific losses: Influenced by composition of the raw material