Effect of protein levels and space allocations on performance of growing-finishing pigs

We conducted two trials with growing-finishing pigs (Pig Improvement Company line 405 x Camborough 15) to evaluate the effects of space allocation on performance and CP requirements. In Trial 1, a 2 x 3 factorial (two levels of space, three CP regimens) was used with 252 pigs. Pigs were allocated to either .23, .28, .37, or .50 m2 per pig (crowded) or .37, .47, .60, or .74 m2 per pig (uncrowded) during the 18 to 36, 36 to 55, 55 to 91, and 91 to 127 kg weight periods, respectively. Diets contained 16.1, 18.6, or 21.1% (18 to 36 kg), 15.3, 17.8, or 20.3% (36 to 55 kg), 14.7, 17.2, or 19.7% (55 to 91 kg), and 12.8, 15.3, or 17.8% (91 to 127 kg) CP. The 16.1, 15.3, 14.7, and 12.8 % CP (control) diets contained 1.09, .86, .82, and .65% lysine, respectively. Crude protein levels (Trials 1 and 2) were achieved by substituting soybean meal for corn. In Trial 1, a CP x space interaction ( P < .03) for gain:feed suggested that feed efficiency of grower pigs was improved to a greater extent in uncrowded pigs than in crowded pigs. Grower pigs (18 to 55 kg) with less space had depressed (P < .05) feed intake and gain and a lower (P < .10) feed efficiency than uncrowded pigs. Added CP improved (P < .05) rate and efficiency of gain in grower pigs. Overall (18 to 127 kg), crowded pigs had reductions (P < .05) in gain (17.6%), feed intake (11.3%), and gain:feed ratio (7.1%) compared to uncrowded pigs. Trial 2 involved 216 finishing pigs in a 2 x 2 factorial (two levels of space, two CP regimens). Pigs were provided with either .37 or .50 m2 per pig (crowded) and .60 or .74 m2 per pig (uncrowded) during the 55 to 91 and 91 to 127 kg weight periods, respectively. The diets contained 14.1 or 17.1% CP (55 to 91 kg) and 12.1 or 15.1% CP (91 to 127 kg). Lysine levels were .67 and .53% for the 14.1 and 12.1% CP diets, respectively. Overall (55 to 127 kg), crowded pigs had depressed (P < .05) gains (15.4%), feed intakes (9.5%), and feed efficiencies (6.8%) compared with uncrowded pigs. Increasing CP resulted in improved (P < .05) ADG (7.4%) and gain:feed (8.3%) in crowded and uncrowded pigs. The data suggest that pigs with lower feed intakes as a result of space restrictions do not have higher CP requirements than those with more space.