Methionine requirement of male white Pekin ducklings

Two experiments were conducted to determine the methionine (Met) requirement of male White Pekin ducklings. In each study, day-old ducklings were raised in electrically heated battery brooders and fed a corn-peanut meal basal diet (dry mash) supplemented with either 0, .06, .12, .18, .24, or .30% L-Met. Based on the analysis of corn and peanut meal, the basal diet contained 22% crude protein .268% Met, and .284% cystine (Cys). The energy content of the basal diet was calculated to be 2914 kcal ME/kg. Regression analysis of 12- day weight gain data pooled across experiments indicated a quadratic trend. When the quadratic model was solved for 95% of maximum growth, a Met requirement of .422% was predicted (r2 = .49). Analysis of the pooled weight gain data by the broken-line method yielded a requirement estimate of .382% (r2 = .50). Therefore, the duckling's calculated Met requirement most likely lies between .382 and .422% (.666 and .706% total sulfur amino acids, respectively). This .04% discrepancy between models for predicting the duckling's Met requirement is probably of minor practical significance, considering the variability of Met and Cys contents of feedstuffs and the fact that corn-soy diets are usually supplemented with a source of Met activity that includes a margin of safety.