Material Collected in a Metabolic Trial

Correct Answer: Both urine and faeces

Metabolic trials collect both faeces and urine to calculate:

• Nitrogen balance: N intake − (N faeces + N urine) = N retained
• Metabolisable Energy (ME): GE − Faecal energy − Urinary energy − Methane energy

Why Urine is Essential

Urine contains protein catabolism end-products: urea, creatinine, allantoin (from microbial purine nucleotides). Without urine, total N excretion cannot be calculated.

Castrated males preferred — separate urinary and faecal excretion openings allow clean uncontaminated collection.