Answer: CRI (Colour Rendering Index) is a human-centric metric and is not directly meaningful for birds. Poultry respond to specific peak wavelengths, not to how 'natural' a light looks to people. Use a spectrum tuned per species and phase — red around 660 nm for broilers, a balanced white for layers — rather than chasing a high CRI number.
The limitation of CRI
CRI measures how well a light renders colours for the human eye against a reference. It says nothing about whether the spectrum matches a chicken's four-cone vision or hits the peaks that drive growth and laying.
What actually matters
Birds respond to peak wavelength and the red:blue ratio. A high-CRI 'white' tube can still have the wrong peaks for a broiler; a purpose-tuned spectrum can look odd to you yet perform better for the flock.
Per-phase tuning
Hatchery, brooder, grower and layer phases each want a different spectrum. Custom-tuning to those peaks outperforms any fixed high-CRI tube.
What to ask a supplier
Skip 'what CRI?' and ask 'what peak wavelengths, and can you tune them per phase?'. See how IWAY tunes poultry spectrum by phase.