Effect of dietary protein fluctuations and space allocation on performance and carcass quality of growing-finishing pigs.

Two trials with growing-finishing pigs were conducted to evaluate the effects of fluctuating dietary CP levels and/or space allocation on performance and carcass traits. In Trial 1, three CP regimens were used with 216 growing-finishing pigs (mixed sex). Average initial and final weights of pigs were 31 and 103 kg, respectively. The CP regimens consisted of: 1) control (18% CP from wk 0 to 4; 15% CP from wk 4 to 12); 2) moderate CP variations (MCPV = 19.5% CP from wk 0 to 2, 16.5% CP from wk 2 to 6, 13.5% CP from wk 6 to 8, 16.5% CP from wk 8 to 10, 13.5% CP from wk 10 to 12); and 3) extreme CP variations (ECPV = 21% CP from wk 0 to 2, 15% CP from wk 2 to 4, 18% CP from wk 4 to 6, 12% CP from wk 6 to 8, 18% CP from wk 8 to 10, 12% CP from wk 10 to 12). Overall (wk 0 to 12), treatment differences were not observed (P > 0.05) for gain, feed intake, CP intake, gain:feed ratio, or gain/CP intake. Trial 2 involved 360 finishing pigs (mixed sex) in a 3 x 2 factorial arrangement (three dietary CP regimens, two floor space allowances). The diets consisted of: 1) control (16% CP from wk 0 to 4, 15% CP from wk 4 to 8; 14% CP from wk 8 to 12); 2) MCPV (17.5% CP from wk 0 to 2, 14.5% CP from wk 2 to 4, 16.5% CP from wk 4 to 6, 13.5% CP from wk 6 to 8, 15.5% CP from wk 8 to 10, 12.5% CP from wk 10 to 12); and 3) ECPV (19% CP from wk 0 to 2, 13% CP from wk 2 to 4, 18% CP from wk 4 to 6, 12% CP from wk 6 to 8, 17% CP from wk 8 to 10 wk, 11% CP from wk 10 to 12). Pigs were provided with either 1.12 m2 (uncrowded; five pigs/pen) or 0.56 m2 (crowded; 10 pigs/pen). Average initial weight was 49 kg and final weights were 126 kg (uncrowded) and 118 kg (crowded). Overall (0 to 12 wk), crowded pigs had lower (P < 0.05) ADG (822 vs. 916 g) and feed (as-fed) intakes (2,633 vs. 2,876 g) than uncrowded pigs. At the end of the 12-wk trial, a control vs. ECPV x space interaction (P < 0.05) occurred for weight gain, fat depth, and percentage of lean. Thus, uncrowded pigs fed ECPV gained faster (933 vs. 887 g) but had a lower percentage of lean (53.5 vs. 54.5) than controls, whereas crowded pigs on the ECPV regimen gained more slowly (812 vs. 842 g) but were leaner (54.8 vs. 54.6%) than those on the control CP regimen. Despite the wide dietary CP fluctuations, pigs in both trials consumed about the same quantity of CP during the 12-wk feeding periods. These data suggest that uncrowded pigs respond differently than crowded pigs to fluctuating levels of dietary CP.