Chronic welfare restrictions and adrenal gland morphology in broiler chickens

Minimal Effects of Rearing Enrichments on Pullet Behaviour and Welfare

In Australia, free-range pullets are typically reared indoors, which may hinder later adjustment to outdoor access. Rearing enrichments could optimise pullet development. Hy-Line Brown® chicks (n = 1700) were reared indoors across 16 weeks with 3 enrichment treatments: (1) a standard control; (2) novel objects (novelty) provided weekly or (3) perching structures (structural) provided. All pullets were weighed at 5, 8, 12, and 16 weeks old. Pullets (n = 87) were tested in a novel arena at 9 weeks and manual restraint (n = 90) at 16 weeks. At 15 weeks, lymphoid organs were extracted and weighed from 90 pullets. Pullets were transferred to the free-range facility at 16 weeks and housed in 9 identical pens within rearing treatments. Hens perching were counted via video recordings across the first week. The structural pullets had the highest relative adrenal weights (p = 0.03) but differences may not have been biologically relevant. Structural hens perched less than the novelty hens in the layer facility (p = 0.02). There were no other consistent rearing treatment differences. The rearing environments had minimal effects on pullet behaviour and welfare, but data from the adult hens did show some longer-term welfare impacts.