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Effect of dietary protein and lysine fluctuations in the absence and presence of ractopamine on performance and carcass quality of late-finishing pigs

M. S. Edmonds^* and D. H. Baker

^* Kent Feeds, Inc., Muscatine, IA Department of Animal Sciences, University of Illinois, Urbana, IL

michael_edmonds{at}kentfeeds.com

Abstract

Two trials with finishing pigs were conducted to evaluate the effects of fluctuating dietary CP levels and ractopamine on performance and carcass traits. In Trial 1, 408 finishing pigs (mixed sex) were assigned to 1 of 4 protein regimens. Average initial and final weights were 89 and 123 kg, respectively. Pigs on treatments 1 to 4 were fed 16, 11, 16 and 13% CP from wk 0 to 2, respectively. During wk 2 to 5, the pigs on regimens 1 to 4 were then fed 15, 18.33, 18 and 20% CP, respectively, with regimens 3 and 4 also containing supplemental ractopamine (9.9 mg/kg) during wk 2 to 5. Overall (wk 0 to 5), gain, gain:feed, loin depth, percentage lean and dressing percent were improved (P < 0.05) in pigs on regimens 3 and 4 vs. those on regimens 1 and 2. No statistically significant overall (wk 0 to 5) protein sequence regimen differences occurred between the standard regimens (1 and 3) and the low-high CP regimens (2 and 4). Trial 2 involved 172 finishing pigs (mixed sex) in 2 protein regimens. Average initial and final weights were 91 and 136 kg, respectively. The diets consisted of: 1) control (16% CP from d 0 to 14, 18% CP + 4.95 mg ractopamine/kg from d 14 to 24, and 18% CP + 9.9 mg ractopamine/kg from d 24 to 35; 2) a low-high CP regimen (12.5% CP from d 0 to 14, 20.33% CP + 4.95 mg ractopamine/kg from d 14 to 24, and 20.33% CP + 9.9 mg ractopamine/kg from d 24 to 35. During d 0 to 14, pigs fed the low CP diet (12.5% CP) had reduced (P < 0.05) gain and gain:feed compared to those fed the control diet (16% CP). In contrast, during d 14 to 35, pigs on the low-high regimen had improved (P < 0.08) gain and gain:feed compared to pigs on the control regimen. Despite the wide dietary CP fluctuations for pigs in Trial 2, performance, and carcass traits were similar for both regimens over the 35-d test period. These data indicate that pigs fed deficient CP and lysine levels for 14 d followed by high CP and lysine levels during a subsequent 21-d period can recover and achieve growth performance and carcass merit equal to that achieved with a conventional protein feeding regimen.

Key Words: compensatory growth • pigs • protein level • ractopamine