Growth, Body Chemical Composition, and Tissue Deposition Rates of Nursery Pigs Fed Crystalline or Protein- Bound Lysine

A 4-wk experiment was conducted to compare the effect of feeding crystalline lysine relative to the lysine from soybean meal (SBM) on growth performance, body chemical composition, and tissue deposition rates in nursery pigs. Thirty-six pigs were used [18 barrows and 18 gilts, 15 d old; initial BW (mean ± SEM) = 6.11 ± 0.11 kg]. Six pigs (3 barrows and 3 gilts) were killed at the beginning of the experiment and the remaining pigs were killed at the end of the experiment to determine body chemical composition and deposition rates of protein, fat, water, ash, and amino acids. Pigs were blocked by sex and BW (3 blocks of barrows and 3 blocks of gilts) and randomly allotted to 1 of 5 dietary treatments. Pigs were individually penned in 2 nursery facilities, and each treatment was replicated 6 times. The dietary treatments consisted of a corn-SBM basal diet (1.05% lysine) and diets containing either 1.15 or 1.25% total lysine, which were achieved by adding lysine (0.10 or 0.20%) from either SBM or l-lysine hydrochloride (crystalline lysine) to the basal diet. Pigs were given ad libitum access to feed during a 28-d period. Blood samples were collected on the last day of the experiment, and plasma was analyzed for urea concentration. Average daily gain, ADFI, and G:F were similar among dietary treatments (P > 0.50). Pigs fed diets supplemented with lysine from SBM had greater (P < 0.001) plasma urea concentrations than pigs supplemented with crystalline lysine. Body protein concentration was greatest (P < 0.01) in pigs consuming the diet with 0.10% added lysine from crystalline lysine. However, protein deposition was similar in pigs fed both supplemented diets (P > 0.10). Body fat concentration and fat deposition were similar (P > 0.25; P > 0.10) in pigs fed diets supplemented with crystalline lysine or lysine from SBM, respectively. Ash concentration was greatest (P < 0.05) in pigs fed 0.10% added crystalline lysine compared with pigs fed added lysine from SBM. Lysine concentration and deposition were similar in pigs fed crystalline lysine and pigs fed SBM-bound lysine. The results suggest there are no differences in growth, body chemical components, and tissue deposition rate between nursery pigs fed SBM-bound lysine and lysine from l-lysine hydrochloride.