Appropriate Methionine:Lysine Ratio For The Segregated Early-Weaned Pig

Kansas State University Swine Research. A total of 350 crossbred pigs (9.0 2 d old and 8.4 lb +/- 2.5 BW) was used to determine the appropriate methionine:lysine ratio in diets for the segregated early-weaned pig. Two lysine levels (1.8 and 1.4%) and five methionine levels within each lysine level were used in a 2 5 factorial arrangement. Methionine:lysine ratios ranged from 21.5 to 33.5%. From d 0 to 21 postweaning, all diets contained 25% dried whey, 12% lactose, 7.5% spray dried porcine plasma, 6.0% select menhaden fish meal, and 1.75% spray-dried blood meal. The basal diets containing 1.4 and 1.8% lysine were formulated to contain .301 and .387% dietary methionine, respectively. Cornstarch was replaced by Alimet(equivalent to 88% methionine) to provide the four additional experimental methionine concentrations for each lysine level. Cystine contents of all diets within each lysine level were identical at .52 and .66% for the 1.4 and 1.8% lysine diets, respectively. All other amino acids were formulated on a digestible basis to ensure that methionine was first limiting. No methionine lysine interactions were observed throughout the 21-day experiment. Increasing dietary methionine increased average daily gain (ADG) during each week of the trial, with the maximum observed at approximately .50 and .39% methionine in the diets containing 1.8 and 1.4% dietary lysine, respectively (27.5% of lysine). Dietary methionine level had no effect on feed efficiency (F/G). Increasing dietary lysine improved ADG and F/G. In conclusion, with either dietary lysine level used, maintaining methionine at 27.5% of lysine was required to maximize growth from d 0 to 21 postweaning.