Influence of crystalline or protein -bound lysine on lysine utilization for growth and protein deposition in nursery and growing pigs

A preliminary study and a 4-wk experiment was conducted to determine the efficiency of utilization of crystalline lysine relative to the lysine in soybean meal for growth performance, protein deposition (PD) and effects on plasma urea concentrations in nursery pigs. The requirement was approximately 1.35% lysine in the preliminary experiment. The dietary treatments in the 4-wk experiment consisted of a basal diet (1.05% lysine) and diets containing 1.15 and 1.25% lysine that were achieved by adding lysine to the basal diet from either soybean meal (SBM) or L-lysine·HCl (crystalline lysine). Growth performance was similar among dietary treatments (P \u3e 0.10). Protein deposition was similar for both supplemented-diets. The efficiency of lysine utilization for PD was similar between sources. Two 4-wk experiments were conducted to determine lysine utilization for growth and carcass traits in barrows and gilts fed individually or in groups. One hundred twelve growing pigs were used in each experiment. Pigs were fed individually or in groups of three. Dietary treatments consisted of a basal diet (0.55% lysine) and diets containing 0.65, 0.75, and 0.85% lysine that were achieved by adding lysine to the basal diet from either SBM or L-lysine·HCl. At the end of the experiment, pigs fed individually were slaughtered. Growth performance and carcass traits were similar between sources (P \u3e 0.10). Plasma urea concentrations decreased for pigs consuming crystalline-supplemented diets and increased for pigs consuming SBM-supplemented diets during the 4-wk experimental period. Body PD increased linearly with dietary lysine concentration (P \u3c 0.01) but was not different between the two sources of lysine at the same concentration. Barrows and gilts had similar PD. Body fat concentration decreased (P \u3c 0.01) as the dietary lysine concentration increased for both lysine sources. Water deposition increased with dietary lysine concentration (P = 0.05). The results suggest that growth and PD of growing and nursery pigs fed lysine from SBM is similar to that of pigs fed crystalline lysine