The effect of phase-feeding on the growth performance, carcass characteristics and nitrogen balance of growing and finishing pigs

A completely randomised design experiment was conducted to determine if grouphoused grower-finisher pigs (43.9 to 95 kg) show differences in performance and nitrogen utilisation when provided with a single high lysine diet (11 g/kg) or with a mean lysine concentration of 9.5 g/kg, either as a single diet or as a series of two or four diets. Four hundred and forty pigs were assigned to four dietary treatments. The experimental treatments were (total lysine) (1) 11 g lysine/kg from day 0 to slaughter (SHD) (2) 10.5 g/kg lysine from day 0 to day 28 and 8.5 g/kg lysine from day 29 to slaughter (DFD) (3) 9.5 g/kg lysine from day 0 to slaughter (RFD) and (4) 11 g/kg lysine from day 0 to day 14, 10 g/kg lysine from day 14 to day 28, 9.0 g/kg lysine from day 28 to day 42 and 8.0 g/kg lysine from day 42 to slaughter (PFD). The estimated lysine concentration required for treatments RFD, DFD and PFD was 9.5 g/kg for group-housed pigs. All diets were pelleted and formulated to have a net energy concentration of 9.8 MJ/kg. The pigs were group fed in mixed-sex pens using single space feeders (11 pigs/feeder, 6 boars and 5 gilts). Daily feed intake was lower (P < 0.05) in treatment SHD in comparison to RFD and DFD during the overall grower-finisher period (2.08 vs 2.18 and 2.23 kg/day, respectively). Lysine conversion ratio was poorer for pigs on treatment SHD compared with DFD (P < 0.01), RFD (P < 0.01) or PFD (P < 0.001), while food conversion ratio was better for pigs on treatment SHD compared with treatments DFD (P < 0.01) and PFD (P < 0.001) during the grower-finisher period (2.31 vs 2.43 and 2.48 kg/kg, respectively). N intake and excretion were higher (P < 0.001) for pigs offered SHD compared to all other treatments (3.93 vs 3.51, 3.42, 3.40 kg and 2.56 vs 2.14, 2.03, 2.10 kg for SHD vs DFD RFD and PFD for intake and excretion, respectively). N utilisation Irish Journal of Agricultural and Food Research 46: 93–104, 2007