Effect of nutrient density and group size on the performance of growing and finishing pigs given food using single-space feeders

A 2 X 2 X 3 factorial arrangement of treatments used 522 boars to examine the main effects and interactions of season (spring v. summer), number of pigs per pen with a single-space feeder (13 or 16 pigs per pen with a single-space feeder; 0.78 m(2) per pig v. 0.65 m(2) floor space per pig) and nutrient density of the diet (12.5 g lysine per kg and 14.0 MJ digestible energy (DE) per kg from 38 kg to slaughter (high), 12.5 g lysine per kg and 14.0 MJ DE per kg during the growing phase and 10.0 g lysine per kg and 13.6 A IJ DE per kg during the finishing phase (split) and 10 g lysine per kg and 13.6 MJ DE per kg from 38 kg to slaughter (low)) on the performance and carcass characteristics of growing and finishing pigs. The smaller group of pigs had a higher food intake during the grower-finisher period than the high stocked pigs (P < 0.01). The pigs had a higher lysine intake in the spring than in the summer months (P < 0.05). Differences in daily food intake for the smaller group of pigs were reflected in increased growth rate during the grower-finisher period (P < 0.001). However these pigs had a poorer food conversion ratio during the grower-finisher period (P < 0.05) than the bigger group of pigs. The pigs offered the high specification and split-fed diets had better growth rate (P < 0.05) than the pigs given the low specification diet during the grower and finisher period. There was a significant two-way interaction in growth rate between dietary treatment and season during the finisher period (P < 0.01). The pigs given the high specification diet had a better growth rate (P < 0.001) than the pigs given the low diets during the summer months. However, the high specification diet depressed growth rate during the spring months (P < 0.05). The pigs had a lower backfat and higher lean meat in the summer than in the spring months (P < 0.05).