Preferred Animals for Digestibility Trials

Correct Answer: Castrated males

Castrated males are preferred because:

• Separate excretion: Faeces and urine pass through separate openings — clean separate collection possible.
• Docile behaviour: No testosterone-driven aggression — easier management.
• Stable metabolism: No reproductive hormonal fluctuations.

Digestibility vs Metabolic Trial

• Digestibility trial: Only faeces collected
• Metabolic trial: Both faeces + urine collected

In poultry, urine and faeces pass through the cloaca together — digestibility determination requires surgical or chemical correction methods.