Animal Science Department


Date of this Version

January 2008


Published in 2008 Nebraska Swine Report. Prepared by the staff in Animal Science and cooperating Departments for use in Extension, Teaching, and Research programs. Copyright © 2007 by The Board of Regents of the University of Nebraska on behalf of the University of Nebraska–Lincoln.
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An experiment was conducted to determine the optimum lysine (lys):Net energy (NE) ratio of low-crude protein (CP) amino acid (AA)-supplemented diets needed in conjunction with ractopamine (RAC) to improve growth performance of late-finishing barrows from the University of Nebraska-Lincoln (UNL) herd. Treatments consisted of jive low CP, AA-supplemented diets with addition of ractopamine (16% CP; 4.5g/ton), formulated to contain 3.35, 3.95,4.57, 5.2 and 5.83 g of lys/Mcal of NE. A corn-soybean meal diet with no RAC supplementation served as negative control (20% CP; 5.24 g of Lys/Mcal of NE). Treatment did not affect growth performance (P > 0.05). Despite the lack of treatment efect (P = 0.09), increasing dietary lys/NE concentration resulted in a linear decrease in final backfat (P = 0.01). Treatments did not affect final longissimus muscle area (P = 0.69). Results indicate that the optimum lys/NE for late-finishing pigs from the UNL herd fed low-CPAA supplemented diets containing 4.5 g of RAC is between 4.57, and 5.2 g of lys/ Mcal of NE.