High dietary phytase levels maximize phytate-phosphorus utilization but do not affect protein utilization in chicks fed phosphorus- or amino acid-deficient diets.
Four trials investigated the effect of high levels of three phytase enzymes on P and protein utilization in chicks. The three phytases were derived from Aspergillus (Fungal Phytase 1), Peniophora (Fungal Phytase 2), and E. coli. Within each assay, 8-d-old male chicks were given ad libitum access to their experimental diet for 10 to 14 d. For Trials 1, 2, and 3, the basal diet was a corn-soybean meal diet deficient in P that was analyzed to contain 23% CP and 0.38% total P (0.10% estimated available P, as-fed basis). Phytase supplementation levels were based on the assessment of phytase premix activity (i.e., P release from Na phytate at pH 5.5 and 37 degrees C). In Trial 1, supplementation of inorganic P from KH2PO4 (0 to 0.20%) resulted in a quadratic (P < 0.05) response in weight gain, gain:feed, and tibia ash concentration but a linear (P < 0.01) increase in tibia ash weight. Tibia ash was higher (P < 0.01) for chicks fed E. coli phytase than for those fed Fungal Phytase 1 at 500, 1,000, and 5,000 phytase units (FTU)/kg, but did not differ between these two phytases at 10,000 FTU/kg. In Trial 2, E. coli phytase supplementation at 1,000 FTU/kg maximized growth and bone responses, whereas addition of either of the two fungal phytases resulted in increasing responses up to 5,000 and 10,000 FTU/kg. Dietary addition of Fungal Phytase 2 resulted in the poorest (P < 0.01) responses among the three phytases. Escherichia coli phytase supplementation at 10,000 FTU/kg in Trial 3 resulted in tibia ash (millligrams) responses that were greater (P < 0.05) than those resulting from either 0.35% inorganic P supplementation or 10,000 FTU/kg of Fungal Phytase 1 or 2. Trial 4 showed that E. coli phytase supplementation at either 500 or 10,000 FTU/ kg did not improve protein efficiency ratio (gain per unit of protein intake) of chicks fed low-protein soybean meal or corn gluten meal diets that were first-limiting in either methionine or lysine, respectively. These results demonstrate that high dietary levels of efficacious phytase enzymes can release most of the P from phytate, but they do not improve protein utilization.
Augspurger
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NR
Department of Animal Science, University of Illinois, Urbana 61801, USA.
Baker
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DH
D010832:6-Phytase / Q000008:administration & dosage*; D000596:Amino Acids / Q000172:deficiency / Q000378:metabolism; D000821:Animal Feed; D000818:Animals; D001230:Aspergillus / Q000201:enzymology; D002645:Chickens / Q000378:metabolism*; D004044:Dietary Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D005658:Fungi / Q000201:enzymology; D008297:Male; D010758:Phosphorus / Q000172:deficiency / Q000378:metabolism*; D016226:Phosphorus, Dietary / Q000008:administration & dosage; D010833:Phytic Acid / Q000378:metabolism*; D011897:Random Allocation; D013977:Tibia / Q000378:metabolism; D015430:Weight Gain / Q000187:drug effects
D000596:Amino Acids; D004044:Dietary Proteins; D016226:Phosphorus, Dietary; D010758:Phosphorus; D010833:Phytic Acid; D010832:6-Phytase