Animal Science Department


Date of this Version

January 2003


Published in 2003 Nebraska Swine Report, compiled by Duane Reese, Extension Swine Specialist, Department of Animal Science, University of Nebraska–Lincoln. Published by Cooperative Extension Division, Agricultural Research Division, and Institute of Agriculture and Natural Resources, University of Nebraska–Lincoln.


Experiments have shown that the efficiency of utilization of crystalline amino acids may be lower than that of amino acids bound in protein. A four-week experiment was conducted to determine whether the efficiency of utilization of crystalline lysine was lower than that of lysine in soybean meal for growth and body protein deposition in nursery pigs. A total of 30 pigs (15 barrows and 15 gilts) with initial body weight of 13 lb were blocked by sex and randomly allotted, one per pen, to 30 pens in two nursery facilities. There were six replications per treatment. Six pigs (three barrows and three gilts) were killed at the beginning of the experiment to determine initial body composition. Pigs were fed five dietary composition. Pigs were fed five dietary treatments that consisted of a basal diet (1.05% lysine) and diets containing 1.15 and 1.25% lysine which were achieved by adding lysine to the basal diet from either soybean meal (SBM) or L-Lysine. HCl (crystalline). Blood samples were collected on the last day of the experiment and plasma was analyzed for urea concentration. Average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (ADG/ADFI) were similar (P>0.10) among treatments. The total lysine intake increased as the lysine concentration in the diet increased (P<0.01). Body protein content was affected by diet (P<0.01). For pigs fed diets containing 1.15% lysine, body protein percentage was greater (P<0.01) for pigs consuming crystalline lysine, versus SBM-supplemented diets. However, body deposition rates of protein were not different among treatments. Body fat concentration and body fat deposition were affected by diet (P=0.05 and P<0.10 respectively,) but were similar between the two sources of dietary lysine. No differences were observed among treatments for body lysine concentration or lysine deposition rate. The efficiency of lysine utilization for protein deposition was greatest in pigs fed the basal diet and the crystalline supplemented diet at 1.15% total lysine. However, at the dietary concentration of 1.25% lysine, the efficiency was similar between sources. Pigs fed diets supplemented with SBM had greater (P<0.01) plasma urea concentrations than pigs supplemented with crystalline lysine. Based on these results, it is concluded that there are no differences in the efficiency of utilization between SBM-bound lysine and lysine from L-lysine•HCl for growth and protein deposition in nursery pigs.