2.1. Study description
A total of 60 healthy Rasa Aragonesa male lambs (65 days old) with
an average live weight of 17.13 (±0.18) kg, were allocated into two
treatments (weights were balanced across treatments) according to
their pen environment during the finishing phase of fattening, which
lasted five weeks. Lambs were housed indoors in six pens with 10
lambs each (2.9 × 3.3 m, animal density of 0.95 m² per lamb) and
three replicates per treatment. The lambs from the enriched environment
(EE) were maintained in pens with a wooden platform with
ramps that provided access to a concentrate hopper (Fig. 1). The platform
dimensions were 2.35 m long, 1.55 m wide and 0.35 m high
(1.67 m²). The ramp slope was approximately 20°. The platform in the
pen was attached to the solid fence that separated each pen, allowing
the lambs to feed, explore or rest lying down. The lambs from EE were
provided with cereal straw as bedding on the floor and as forage in a
fodder rake. Additionally a small ramp (0.90 m long, 0.50 m wide, 0.35