Nutrient and energy utilization in enzyme-supplemented starter and grower diets for White Pekin ducks

The aim of this study was to determine the effect of enzyme supplementation on energy and nutrient utilization in White Pekin ducks fed starter and grower diets. In each of 2 experiments, 8 ducks were assigned to each starter or grower diet without or with enzyme supplementation at 1 g/kg of diet in a 2 x 2 factorial arrangement of treatments for a 120-h nutrient utilization assay. Starter and grower diets in experiment 1 contained 3.68 and 2.51% N, respectively, and 4.321 and 4.274 kcal/ g of gross energy, respectively. Corresponding values in experiment 2 were 2.93 and 2.89% and 3.994 and 3.930 kcal/g. The enzyme supplement was a cocktail containing 7,500 units of protease and 44 units of cellulase per gram. Endogenous energy losses were from 23 to 44 kcal in the 2 experiments, and endogenous amino acid (AA) losses ranged from 14 mg for Trp to 137 mg for Asp. In experiment 1, a lower energy output of ducks fed the grower diet, coupled with lower N output, resulted in greater (P < 0.05) diet AME(n) for the grower than the starter diet. Apparent digestibilities of all AA were higher (P < 0.05) in the starter diet than in the grower diet regardless of enzyme supplementation, more so for the S-containing AA. Average true digestibility of all AA was 93.7 and 90.4% for the starter and grower diets, respectively. There was no effect of enzyme supplementation of diet on the true digestibility of AA except for Met. Average true digestibility of all AA for diets not supplemented or supplemented with enzyme were 91.3 and 92.8%, respectively. In experiment 2, energy utilization of the grower diet was higher (P < 0.05) than that of the starter diet. Lysine and Asp showed lower (P < 0.05) apparent digestibility in the grower than in the starter diet. Enzyme supplementation of starter or grower diets did not affect the apparent digestibility of AA, except for Met, whose digestibility was increased by 2.4 percentage points in an enzyme-supplemented diet (P < 0.05). Except for Trp, true digestibility of AA was not affected by diet type or enzyme supplementation. The results show that the enzyme cocktail evaluated improved AA and energy utilization in White Pekin ducks and that such an enzyme-related response is diet composition-dependent.