Standardized ileal digestible lysine requirements based on growth performance of White Pekin ducks for 21 days after hatch

The purpose of this study was to assess the optimal standardized ileal digestible (SID) lysine (Lys) requirement for male White Pekin ducklings with a specific focus on growth performance for the 3 weeks following hatching. A total of 384 one-day-old male White Pekin ducklings were allocated to six different dietary treatments, each containing varying levels of digestible Lys content ranging from 0.72% to 1.12%. All amino acids in the diets remained consistent except for Lys. The ducklings were randomly distributed into 24-floor pens, with each treatment group comprising eight pens, and each pen housing eight ducklings. The diets were offered <italic>ad</italic>-<italic>libitum</italic> throughout the study. Weekly measurements of body weight and feed intake were recorded to calculate the feed conversion ratio. The SID Lys requirement was determined by analyzing the data using both linear-plateau and quadratic-plateau models and calculating the mean value. The results demonstrated a significant linear (<italic>P</italic> &lt; 0.001) and quadratic (<italic>P</italic> &lt; 0.001) improvement in body weight gain and feed efficiency with increasing SID Lys content in the diet. According to the linear-plateau regression analysis, the estimated SID Lys requirements for final body weight, weight gain, and feed efficiency were 1.00%, 1.00%, and 0.98%, respectively. Conversely, the quadratic-plateau regression analysis yielded estimated SID Lys requirements of 1.11%, 1.11%, and 1.10%, respectively, for the same parameters. In summary, this study established that the recommended SID Lys levels for White Pekin ducklings for the 3 wk period after hatching were found to be 1.05%, 1.05%, and 1.04% for achieving the finest final body weight, daily gain, and feed efficiency, respectively.