August 19, 2019

Interpretive Summary: Bioavailability of l-Lys HCl vs l-Lys sulfate

Interpretive Summary: Bioavailability of l-lysine sulfate relative to l-lysine HCl for growing–finishing pigs.

By: Anne Wallace

Lowering the crude protein (CP) content of commercial pig-feed is desired as it reduces gastrointestinal distress, diarrhea, and excreted fecal nitrogen in pigs. However, the essential amino acid lysine (Lys) is a limiting amino acid in soybean meal and grain-based diets. Therefore, reducing CP requires supplementing Lys in the feed. Ways to ensure swine cost-effectively meet lysine requirements in the context of reduced CP are necessary. 

Currently, l-Lys HCl is the primary Lys supplement used. In this study published in the July 2019 issue of Translational Animal Science, the relative bioavailability (RBV) of l-Lys HCl versus l-Lys sulfate in early and late grower pigs was evaluated. Blood and fecal samples of studied pigs were collected to measure blood urea nitrogen (BUN), digestibility of dry matter (DM) and sulfur (S); carcass characteristics were also determined. The goal was to determine how l-Lys sulfate affected growth performance compared to l-Lys HCl.

A total of 280 pigs were fed one of seven diets over 112 days, as follows: Lys-deficient basal diet providing 65% or required lysine, or a basal diet containing 75%, 85%, or 95% Lys supplemented from either l-Lys HCl or l-Lys sulfate. Pigs were housed 5 per pen in 56 pens. The diets were split into four phases with the fourth phase ending as pigs reached market weight.

Diets with a higher content of Lys, regardless of Lys source, increased body weight, average daily gain, and feed efficiency of studied pigs. There was a linear increase in growth performance and a decrease in backfat. There was no difference in BUN, digestibility of DM or S, and RBV based on Lys source. Overall, there were no significant differences found between l-Lys HCl and l-Lys sulfate, supporting the findings of previous studies.

To conclude, the results of this study suggest that l-Lys HCl and l-Lys have similar bioavailability in growing-finishing pigs. Expanding study parameters to include different populations or growing conditions (e.g., gestating or lactating sows) may be warranted.

To view the article, visit Translational Animal Science.