Growth and the plasma concentrations of growth hormone and prolactin in chicks: Effects of 'environmental enrichment', sex and strain (1980)

Jones, R. B., Harvey, S., Hughes, B. O. et al.

Abstract

The enriched boxes were similar to the bare ones but also contained the following objects: two large red rubbing bungs, a golf ball, a bottle top, two coloured table tennis balls hanging from the cage lid, two lengths of string... The present results indicate that environmental enrichment has a growth-stimulating effect.