Supplementing L-Lysine is about as common in swine diets as supplementing with salt.

A common rule of thumb when formulating swine diets is that 3 lb. of L-Lysine plus 97 lb. of corn can substitute for 100 lb. of soybean meal. This substitution has generally reduced diet costs because of economically priced L-Lysine and $2/bu. ($0.036/lb.) or less for corn.

As the price of corn jumped approximately $1.50/bu. ($0.027/lb.), the cost of a grower-finisher diet increased over $35/ton of complete feed while reducing the opportunity price of L-Lysine.

Before the price increase, swine diet formulation centered on minimum protein (or amino acid) levels and the maximum use of synthetic amino acids — primarily L-Lysine. This thinking needs to be reevaluated with $3.50/bu. ($0.063/lb.) corn, because the higher cost may delete synthetic L-Lysine from the diet in favor of soybean meal.

In Table 1, a typical 0.9% total lysine (0.74% digestible lysine) corn-soybean meal diet containing 3 lb./ton of L-Lysine was used as a base diet to evaluate “what if” comparisons for various corn and soybean meal prices and to determine the resultant opportunity price for L-Lysine. The opportunity price suggests the maximum price one can afford to pay for L-Lysine before being rejected from the formulation in favor of soybean meal.