The effect of trough space and floor space on feeding and welfare of lambs in an intensive finishing system

•Both floor space and feeder space may affect adaptation of lambs to a feedlot.•Increasing feed trough space from 4 to 10cm/lamb increased total time feeding.•Increased feed trough space resulted in greater growth rates.•No effect on feeding behaviour and on growth was found with increased floor space. This study examined the effects of floor space and feeder space on the feeding behaviour, growth and stress physiology of lambs, at different times, over a 6-week period in a finishing feedlot. A total of 640 lambs in four time replicates (160 lambs per replicate) were studied in four 40-lamb intensive finishing systems (feedlots) for 6 weeks over a 16-month period. The lambs were Merino wethers with live weight at the commencement of the experiment of 28.3 (s.d.=2.4)kg. The effects of two factors, pen floor space (2 and 5m2/lamb) and feed trough space (4 and 10cm/lamb) were examined in a factorial arrangement. Measurements taken on individual lambs during the experimental period included: feeding behaviour and displacements at the feeder in the feedlot during weeks 1, 2 and 6, lying behaviour during week 3, weekly live weights and cortisol concentrations in weeks 1 and 6. Weekly feed intake for each group of lambs was also record. Trough space of 4cm compared to 10cm per lamb reduced average lamb feed intake in all weeks of the 6-week period (a reduction of 1.2 (s.e.=0.53) kg/hd in week 1, 1.3 (s.e.=0.62)kg/hd in week 2, weekly average of 0.9 (s.e.=0.17)kg/hd over weeks 3–6; P=0.05, P=0.06 and P=0.0004, respectively). However, weight gain only differed significantly during the first week in the feedlot (average of 0.2 vs 1.1 (s.e.d.=0.35)kg for 4cm vs 10cm/lamb of provided trough space, P=0.03). At all observed times within the 6-week period, lambs with the reduced feed trough space spent less total time feeding (P