Search

An experiment was conducted to evaluate increasing or decreasing concentrations of dietary phytase on growth performance and processing yields of male broilers from 1 to 35 d of age. Treatments consisted of a positive control, a negative control (NC; less 0.14% Ca, 0.13% nonphytate P, and 0.03% Na), and 6 additional treatments based on the NC supplemented with phytase. Treatments 3 through 5 consisted of the NC diet supplemented with 500 phytase units (FTU)/kg of phytase in the starter phase that was either continued throughout the remainder of the study (treatment 3) or increased to 1,500 FTU/kg beginning in the finisher (treatment 4) or grower (treatment 5) phases. Treatment 6 had 1,500 FTU/kg of phytase throughout the study. Treatments 7 and 8 had 1,500 FTU/kg in the starter and decreased to 500 FTU/kg in the finisher or grower phases, respectively. At 35 d of age, broilers fed diets containing 1,500 FTU/kg of phytase had increased BW gain compared with birds fed diets formulated to contain 500 FTU/kg of phytase. Increasing phytase concentration between the starter and grower phases or decreasing phytase concentration between the grower and finisher phases negatively affected FCR from 1 to 35 d of age. Phytase supplementation did not affect weight and yield of carcass characteristics. Therefore, dietary phytase concentration should not be varied throughout production for optimum growth performance. [ABSTRACT FROM AUTHOR]

The objective was to determine the effects of extractable salt-soluble protein content of corn (PS) and exogenous enzyme supplementation on N, starch, and energy digestibility in broilers fed diets adequate in Ca and nonphytate P. Broilers were randomly distrib-uted into floor pens (6 replicate pens per treatment) with 28 birds per pen at 1 d of age. Treatments consist-ing of 4 sources of corn varying in PS (A, 58.1; B, 54.2; C, 53.7; and D, 30.6 nig of BSA equivalent values) with or without phytase (0 and 1,000 phytase units/kg) and xylanase (0 and 16,000 units of xylanase activity/kg) were randomly assigned to each pen. Different sources of corn were provided from 1 to 9 and 24 to 29 d of age. However, enzyme treatments were provided throughout the experiment. From 1 to 9 d of age, no interactions were observed. Apparent ileal N digestibility (AIND) and apparent ileal digestible energy (IDE) of diets with the lowest PS (based on corn D) were lower (P ≤ 0.05) than those of diets with a higher PS. Phytase increased (P ≤ 0.01) AIND and IDE by 5 and 16%, respectively, and xylanase exerted the opposite effect (P ≤ 0.03). From 24 to 29 d of age, phytase and xylanase in com-bination resulted in reduced (P ≤ 0.05) AIND of diets with a low PS (based on corn D) compared with the basal diet in broilers. Broilers fed diets with the high-est or lowest PS (based on corn A or D) had lower (3-way interaction; P ≤ 0.05) IDE when phytase and xylanase were supplemented in combination compared with either enzyme alone. In conclusion, responses to exogenous enzyme supplementation are not constant and are influenced by the source of ingredients as well as the age of broilers. The magnitudes of the responses to phytase on nutrient and energy digestibility were greater at 9 compared with 29 d of age. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to evaluate the extra-phosphoric effects of phytase on amino acid (AA) and energy digestibility (experiments 1 and 2) and growth performance (experiment 2) of broilers fed diets adequate in Ca and nonphytate P supplemented with xylanase. Ross x Ross 708 broiler chicks (864 males in experiment 1 and 1,152 females in experiment 2) were randomly distributed into battery cages (6 replicate cages per treatment) with 12 birds per cage at 1 d of age. In both experiments, factorial arrangements of treatments were evaluated consisting of 6 phytase [0, 1,000, 2,000, 4,000, 8,000, or 16,000 phytase units (FTU)/kg] and 2 xylanase [0 or 16,000 birch xylan units (BXU)/kg] concentrations in experiment 1 and 4 phytase (0, 500, 1,000 or 2,000 FTU/kg) and 4 xylanase (0, 8,000, 16,000, or 32,000 BXU/kg) concentrations in experiment 2. Treatments were provided from 27 to 32 d of age in experiment 1 and from 1 to 32 d of age in experiment 2. Digesta contents of the terminal ileum were collected at 32 d of age (experiment 1 and 2), and growth performance was measured at 1, 14, and 25 d of age in experiment 2. There was no interaction of phytase and xylanase; only main effects of phytase were observed. In experiment 1, broilers fed diets supplemented with phytase at 1,000 FTU/kg had increased (P < 0.05) apparent ileal digestibility (AID) of all A A with the exception of Ala and Met. Diets fed to broilers supplemented with higher concentrations of phytase did not further increase AID of any A A (P > 0.05) above the addition of 1,000 FTU/kg of phytase. Phytase supplementation did not affect ileal digestible energy (P > 0.05). For all variables measured, significant log-linear or log-quadratic effects of phytase (P > 0.05) were not observed. In contrast, broilers fed diets supplemented with phytase in experiment 2 exhibited log-linear (P < 0.05) increases in AID of AA but not apparent ileal digestible energy. However, supplementation with 2,000 FTU/kg of phytase increased (P = 0.05) ileal digestible energy by 36 kcal/kg compared with the basal diet. Broilers fed diets with 1,000 FTU/ kg of phytase had improved growth performance (P < 0.05) in comparison with broilers fed diets containing 0 or 500 FTU/kg of phytase. The addition of 500 FTU/ kg of phytase in diets fed to broilers did not affect ileal digestibility or growth performance (P > 0.05). Data obtained from these experiments demonstrated extra-phosphoric effects in broilers fed diets supplemented with 1,000 FTU/kg of phytase and diminishing returns with higher concentrations. [ABSTRACT FROM AUTHOR]