The Optimal True Ileal Digestible Lysine and Threonine Requirement for Nursery Pigs

A total of 360 pigs (initially 22.2 lb and 31 d of age) was used in a 21-d growth assay. This trial was conducted as a combination of two separate trials in order to simultaneously examine both the true ileal digestible lysine and true ileal digestible threonine requirement and determine the appropriate threonine:lysine ratio. The first part of the trial consisted of five treatments with increasing dietary lysine (1.0. 1.1, 1.2, 1.3 and 1.4% true digestible lysine). The second part consisted of five treatments with increasing dietary threonine (0.66, 0.72, 0.78, 0.84 and 0.91% true ileal digestible threonine). The highest level of both lysine and threonine (1.4% and 0.91% respectively) served as a positive control, and this diet was combined as one treatment to give a total of nine treatments. Average daily gain increased to 1.3% true ileal digestible lysine, and then plateaued, while ADG increased to 0.78% true ileal digestible threonine, suggesting a threonine:lysine ratio of 60% for ADG. Increasing dietary lysine improved F/G linearly through 1.4% true ileal digestible lysine, while F/G improved up to a level of 0.84% true ileal digestible threonine. Using a level of 1.4% true ileal digestible lysine, a threonine:lysine ratio of approximately 60% is implicated for F/G.