Body composition, tissue deposition, and lysine utilization for protein deposition of barrows and gilts fed crystalline or protein-bound lysine

An experiment with 2 trials (28 d/trial) was conducted to determine body composition, tissue deposition, and utilization of Lys for protein deposition (PD) of barrows and gilts fed L-Lys·HCl (CLys) or protein-bound Lys in soybean meal (SBM). Thirty two growing pigs (16 barrows and 16 gilts; average initial BW of 18.6 kg) were used in each of 2 trials. Four pigs (2 barrows and 2 gilts) were euthanized at the start of each trial to determine initial body composition. The remaining pigs were euthanized at the end of the trials to determine empty-body composition and deposition rates of water, protein, fat, ash, and AA. Pigs were randomly allotted to 1 of 7 dietary treatments. There were 2 replications per treatment in each trial for a total of 4 replications. Dietary treatments consisted of a corn-SBM basal diet (0.48% Lys) and diets containing 0.56%, 0.65%, and 0.74% standardized ileal digestible (SID) Lys that were achieved by adding Lys to the basal diet from either SBM or CLys. Pigs fed the CLys-supplemented diets at 0.65% SID Lys had more (P < 0.05) body water (663 vs. 624 g/kg) and less (P < 0.01) body protein (153 vs. 160 g/kg) than pigs fed the SBM-supplemented diets. Body fat content decreased (P < 0.01) as the dietary Lys increased similarly for pigs fed Lys from SBM and pigs fed CLys. Gilts had greater (P = 0.05) body Lys content in body protein than barrows (7.68 vs. 7.52 g/100 g). Empty-body ash contents were not different between pigs fed CLys or SBM-supplemented diets. Water deposition and PD increased linearly (P < 0.01) with dietary Lys and were least (P < 0.01) in pigs fed the basal diet but were similar when comparing pigs fed CLys and SBM-supplemented diets at the same dietary Lys concentration. Lysine deposition showed a linear increase (P < 0.01) with dietary Lys but was not different between pigs fed the 2 Lys sources at the same concentration. Barrows and gilts did not differ in tissue deposition rates. Overall, empty-body contents and deposition rates of essential and nonessential AA were not different between pigs fed CLys and pigs fed SBM-bound Lys. The amount of SID Lys required for PD ranged between 0.09 and 0.13 g/g for both sources of Lys. The Lys deposition: SID Lys intake ratio was greater (P < 0.01) in gilts than barrows (0.62 vs. 0.56). Body composition, tissue deposition, and utilization of Lys for PD and Lys deposition were not different in pigs fed diets supplemented with L-Lys·HCl with respect to protein-bound Lys in SBM.