A 3-wk feeding trial with 180 sexed day-old broiler chickens was conducted to study the efficacy of microbial phytase (Natuphos 1000) on growth performance, relative retention of P, Ca, Cu, and Zn, and mineral contents of plasma and bone. Treatments involved a normal P level corn-soybean diet, a low-P diet, and a low-P plus phytase (600 phytase units/kg) diet. Phytase supplementation increased (P < or = 0.05) body weight in male and female chickens by 13.2 and 5.8%, respectively, at 21 d. The improvements yielded body weights comparable to those obtained on the normal P diet. Phytase supplementation overcame (P < or = 0.05) the depression of feed intake observed on the low-P diet. Treatments had no effect on feed:gain ratio. Phytase supplementation of the low-P diet increased (P < or = 0.05) the relative retention of total P, Ca, Cu, and Zn by 12.5, 12.2, 19.3, and 62.3 percentage units, respectively, in male chickens. Microbial phytase increased the plasma P by 15.7% and reduced (P < or = 0.05) the Ca concentration by 34.1%, but had no effect on plasma concentrations of Cu or Zn. Phytase supplementation increased the percentage ash in both head and shaft portions of dry, fat-free tibia bone to a level comparable to that of the normal-P diet. Phytase supplementation had no effect on the concentration of any of the minerals measured in whole tibia ash but did increase (P < or = 0.05) the DM percentage of P and Ca min tibia head of male chickens by 0.65 and 1.4 percentage units, respectively. These results show that microbial phytase supplementation of a low-P diet increased growth and relative retention of total P, Ca, Cu, and Zn and improved bone mineralization in broiler chickens.

A 3-wk feeding trial with 240 sexed, day-old broiler chickens was conducted to determine the efficacy of microbial phytase at different levels of dietary Ca on performance and utilization of minerals in broiler chickens fed a low-P corn-soybean diet. The experimental design was a 3 x 2 factorial arrangement of treatments; Ca at 0.6, 1.0, and 1.25% and phytase at 0 and 600 phytase U/kg diet. Phytase supplementation, regardless of Ca level, increased (P < or = 0.005) feed intake, (P < or = 0.0001) body weight, and (P < or = 0.025) feed efficiency at 21 d; the optimum levels of body weight, feed intake, and feed efficiency were obtained with low (0.6%) dietary Ca plus phytase. Retentions of P, Ca, and N were increased (P < or = 0.05) by phytase supplementation. Although maximum retentions of P and N were obtained at the 1.0 and 1.25% Ca levels, respectively, they were not significantly different from the values obtained at 0.6% Ca. The increasing level of dietary Ca decreased plasma P ( P < or = 0.05) and Cu (P < or = 0.06). Phytase supplementation had the opposite effect; i.e., increased plasma P (P < or = 0.03) and Cu (P < or = 0.02). The maximum level of plasma P was obtained with phytase at the 1.0% Ca level, but this value was not significantly different from the value obtained with phytase at the 0.6% Ca level. Phytase supplementation increased (P < 0.04) the ash content of both tibia head and shaft but had no effect on mineral contents in the ash. The optimum level of ash content was observed with the 0.06% Ca diet plus phytase. The results show that microbial phytase supplementation to a low P diet improved growth performance and mineral utilization in broiler chickens. Dietary Ca levels had a significant effect on the response to phytase; the optimum growth performance and mineral utilization were achieved at the low (0.6%) level of dietary Ca supplemented with phytase.

Phytic acid or phytate is a naturally occurring organic complex found in plants. As a reactive anion, it forms a wide variety of insoluble salts with divalent and trivalent cations. Phytic acid is also known to complex with proteins and consequently reduce their availability. Recent studies indicate that phytic acid reduces the activity of pepsin, trypsin and a-amylase. Because of a lack of endogenous phytase, which hydrolyses phytic acid, phytate phosphorus is biologically less available to poultry. Because of the complex factors influencing phytate hydrolysis, such as dietary calcium content, inorganic phosphorus and vitamin D,, and the age and genotype of birds, there is wide disagreement concerning the ability of poultry to utilize phytate phosphorus. Data suggest that the amount of endogenous phytase is extremely low in young birds but that it increases with age. Cereal based poultry diets supplemented with microbial phytase result in increased digestibility and availability of phytate bound phosphorus, calcium, zinc and copper. Microbial phytase supplementation has also been shown to increase ileal digestibility of crude protein and amino acids in female broiler chickens and in female turkeys, but curiously not in male chickens. There is no report to date of such a study in male turkeys. While the efficacy of supplemental microbial phytase depends on its rate of inclusion, on the calcium and phytate phosphorus contents and on the dietary ca1cium:phosphorus ratio, clear benefits have been shown in terms of increased availability of phytate-bound minerals and crude protein, and reduced environmental pollution through lower levels of phosphorus and nitrogen excretion. To maximize the benefit from the addition of microbial phytase, future research should focus on determining the optimum dietary conditions for it to work. Phytic acid and supplemental microbial phytase in poultry: S . Sebastian et al. References ANDERSON, P. A. (1985) Interactions between proteins and constituents that affect protein quality. M. (1980) The effects of phytate on nitrogen utilization and zinc metabolism in young rats. Nutrition Reports International BALLAM, G. C., ENGSTER, H. M. and SNETZINGER, D. C. (1984) Effect of calcium level on the ability of broiler and single comb white leghorn to hydrolyse phytate phosphorus. Poultry Science 63: 61 (Abstract) BARRE, R., CURTOIS, J. E. and WORMSER, G. (1956) Etude de la structure de l'acide phytique au moyen de ses courbes de titration et de la conductivity de ses solutions. Bulletin de Socie'tide Chimie Biologique 36: 455-460 BARTNIK, M. and SZAFRANSKA, I. (1987) Changes in phytate content and phytase activity during germination of some cereals. Journal of Cereal Science 5: 23-28 BIEHL, R. R., BAKER, D. H. and DELUCA, H. F. (1995) Hydroxylated cholecalciferol compounds act additively with microbial phytase to improve phosphorus, zinc and manganese in chicks fed soybased diets. {ournal of Nutrition 125: 2407-2416 BITAR, K. and REINHOLD, J. G. (1972) Phytase and alkaline phosphatase activiti...

The effect of microbial phytase supplementation on CP and amino acid (AA) digestibility was investigated in a 28-d trial using 360 sexed, day-old broiler chickens fed corn-soybean meal diets. The experimental design was a completely randomized one with a 3 x 2 factorial arrangement of treatments. The variables included P and Ca levels and phytase: P and Ca levels were: normal P-normal Ca [0.45% available P (Pa), 1.0% Ca], low P-normal Ca (0.35% Pa, 1.0% Ca), and low P-low Ca (0.35 Pa and 0.6% Ca); and phytase at 0 and 600 U/kg diet. Phytase supplementation increased body weight gain (P < 0.014) and feed intake (P < 0.004) at 19 d in male chickens; in females, phytase increased (P < 0.012) only body weight gain at 19 d. The low P-normal Ca diet reduced (P < 0.05) feed intake and body weight gain in both sexes at 7, 14, and 19 d, compared to the normal P-normal Ca diet; the reduction of Ca in the low P diet prevented the above depression, resulting in body weight gain and feed intake to a level comparable to that of the normal P-normal Ca diet. Microbial phytase supplementation had no effect (P < 0.065) on the apparent ileal digestibility (AID) of CP or any AA except Met and Phe in male broiler chickens. In females, adding phytase increased the AID of all AA except Lys, Met, Phe, and Pro. The low P-normal Ca diet reduced (P < 0.05) the AID of Phe, Asp, and Ser in male chickens and reduced the AID of all the AA except Met and Pro in females compared to the normal P-normal Ca diet. The reduction of Ca in the low P diet prevented the depression of the AID of the AA caused by the low P-normal Ca diet, resulting in AID of AA having a level comparable to that of the normal P-normal Ca diet in both sexes. Phytase supplementation did not have any effect (P > 0.05) on apparent "fecal" digestibility (AFD) of CP or any of the AA in male chickens; however, in female chickens it increased the AFD of Thr, Asp, Glu, and Ser. In summary, phytase supplementation increased growth performance in both sexes; increased AID and AFD of most of the AA, particularly in female chickens. The optimum growth performance and AA digestibilities were obtained with the lowest input of resources, in the low P-low Ca diet supplemented with microbial phytase.

High-moisture ear corn (HMEC) was untreated, treated with propionic acid (PA), or inoculated with a mixture of Lactobacillus plantarum and Enterococcus faecium and allowed to ensile in laboratory silos for 0, 7, 21, 42, 138, or 202 d. The silages were evaluated for fermentation quality, microbial populations, and aerobic stability. In all treatments, silage pH declined rapidly within 7 d, but the rate of decline seemed greatest with the inoculum. The lactic acid content of inoculated HMEC was higher (P < .05) than that of control of PA-treated HMEC. Regardless of treatment, the population of lactic acid bacteria (LAB) increased (P < .1) up to 7 to 21 d of fermentation then declined; LAB counts decreased (P < .05) up to 42 d in control and PA-treated silage but continued to decline until 138 d for inoculated silage. Yeast and mold counts tended to decrease up to 42 d of ensiling then decreased (P < .05) as fermentation progressed. Between 138 and 202 d of ensiling, the control silage showed a marked increase (P < .10) in pH and yeast and mold populations, providing evidence of secondary fermentation; PA treatment and bacterial inoculation prevented secondary fermentation. Inoculation tended to reduce estimates of sample temperature for silage stored for 138 d and exposed to air, but not for the corresponding silage stored for 202 d. Treatment with PA prevented the loss (P > .05) of acetic acid and the rise (P > .05) in pH during air exposure of the 138-d silage; both control and PA-treated silage showed an increase (P < .05) in yeast and mold populations, but the increments were 38% and 23%, respectively. Compared with PA, the relative efficacy of inoculation in improving aerobic spoilage of HMEC depended on the period of silo storage and the criterion used to assess aerobic stability.