Relative bioavailability of l-lysine sulfate is equivalent to that of l-lysine HCl for nursery piglets.

Supplementary l-lysine sources include l-lysine HCl and l-lysine sulfate. l-Lysine sulfate contains at least 50% l-Lys and other components as residues from the fermentation process, other amino acids, and other organic and inorganic substances, being an alternative to l-Lys HCl. The aim of this study was to evaluate the relative bioavailability (RBV) of l-Lys sulfate in comparison with l-Lys HCl and its effects on performance, blood parameters, intestinal functionality, and the apparent total tract digestibility in nursery piglets. A total of 168 female piglets (DB90 × PIC337), weaned at 22 d (BW = 6.29 ± 0.41 kg), were distributed in seven dietary treatments and eight replicates, with three pigs per pen. The experimental period of 42 d was divided into two phases (phase 1, days 0-21; phase 2, days 21 to 42). The basal diet (CON) was lysine-deficient formulated to meet 73% of standardized ileal digestible Lys requirements. For the other diets, the CON was supplemented with three levels (80%, 90%, and 100% of standardized ileal digestible Lys requirements) of l-Lys sulfate (70% l-Lys) or l-Lys HCl (79% l-Lys). There were no significant differences (P > 0.05) in the performance and concentrations of plasma urea and creatinine between the l-Lys sources. The RBV of l-Lys sulfate relative to l-Lys HCl was 106%, 119%, and 117% for effects on ADG, G:F, and plasma urea, respectively. Lys deficiency resulted in a greater (P < 0.05) incidence of diarrhea, while pigs supplemented with Lys sulfate or Lys HCl showed greater (P < 0.05) villus height in the jejunum when compared to those receiving the CON. Diets supplemented with l-Lys sulfate had greater (P < 0.05) apparent total tract digestibility of dry matter, gross energy, and crude protein. In conclusion, the RBV of l-Lys sulfate for effects on ADG, G:F, and plasma urea is equivalent to that of l-Lys HCl for nursery piglets.