Dietary energy level, feeder space, and group size on growth performance and carcass characteristics of growing-finishing barrows and gilts

To benefit from feeding low net energy (NE) diets, growing-finishing pigs must be able to increase feed intake to compensate for lower caloric density, but this might be difficult in pens with a high stocking density. Access to the feeder, trough space, and(or) floor area may limit voluntary feed intake. The objective of this study was to clarify the relationships among dietary NE level, feeder space, group size, sex, and interactions in growing-finishing pigs. In a 2 × 2 × 2 × 2 factorial design, 1,920 pigs (33 kg) housed in 96 fully slatted floor pens (6.1 × 2.4 m) with 2 or 3 feeder spaces, and 18 or 22 barrows or gilts per pen, were fed either low (9.2 MJ/kg) or high (9.85 MJ/kg) NE diets over 5 growth phases (Grower 1: day [d] 0 to 20, Grower 2: d 21 to 41, Grower 3: d 42 to 62, Finisher 1: d 63 to 80, Finisher 2: d 81 to slaughter). Pen body weight (BW) and average daily feed disappearance (ADFD) were measured for each growth phase, biweekly from the start of shipping and at slaughter. Warm carcasses were weighed and graded (Destron). For the entire trial, pigs fed low versus (vs.) high NE diets had 0.119 kg/d greater (P < 0.001) ADFD, but 0.556 MJ/d lower (P < 0.050) average daily caloric disappearance (ADCD), and 0.017 kg/kg lower (P < 0.001) gain-to-feed (G:F). Pens with 18 vs. 22 pigs had 0.062 kg/d greater (P < 0.001) ADFD, 0.730 MJ/d greater (P < 0.010) ADCD, and 0.029 kg/d greater (P < 0.001) average daily weight gain (ADWG). Pigs in pens with 3 vs. 2 feeding spaces had 0.051 kg/d greater (P < 0.010) ADFD, 0.511 MJ/d greater (P = 0.050) ADCD but 0.004 kg/kg lower (P < 0.050) G:F. Pigs fed low vs. high NE diets had 0.6 kg lower (P < 0.050) carcass weight and 0.9 mm lower (P < 0.050) loin depth. Pens with 18 vs. 22 pigs took 2.8 days less (P < 0.001) to reach 130 kg slaughter BW. Pens with 18 vs. 22 pigs had a 0.4 %-point decrease (P < 0.050) in dressing percentage. Feeding low vs. high NE diets reduced (P < 0.001) feed cost by Can$21.87/tonne, $3.34/pig, $0.03/kg gain, and increased (P < 0.05) gross income subtracting feed cost by $1.82/pig. Housing 18 vs. 22 pigs per pen increased (P < 0.010) ISFC by $1.98 per pig. Lack of interactions between NE level, feeder space, and group size for ADFD indicate that low NE diets can be fed to pigs even if they have lower than recommended floor area allowance during part of the finishing phase.