Effects of Aspergillus fumigatus phytase on phosphorus digestibility, phosphorus excretion, bone strength and performance in pigs.
Phytic-phosphorus has a very low bioavailability for monogastric animals and the non-utilized mineral contributes to the phosphorus (P) pollution problems. Phytases may ameliorate phytic-P antinutritive properties. However, phytases are very sensitive to the pelleting temperature commonly used for compound feed production and thus the challenge to produce a more thermostable phytase is very important. Pure Aspergillus fumigatus phytase (AFP) has the ability to refold into a native-like fully active structure after heat denaturation (20 min at 90 degrees C). The aim of the present work was to evaluate in vitro (in feed) and in vivo in young and in growing-finishing pigs the effects of AFP included in the feed at a level of 500 U/kg. Feed supplementation with AFP resulted in an in vitro phosphorus release of about three times higher than that obtained from the basal diets, irrespective of the pH value used for the determination (5.5 or 7). When the supplemented feed was steam pelleted at about 84 degrees C, the free P obtained after incubation at pH 5.5 represented 53% on an average of that obtained from the corresponding mash diets. The phytic-P-rich diets systematically induced hypophosphataemia, hypercalcaemia and hyperphosphatasaemia. The normal blood levels of P, Ca and alkaline phosphatase were restored by AFP. P apparent digestibility was significantly higher for the AFP diet (52.8 versus 30.8%). The improvement in Ca digestibility was not statistically significant. In all three in vivo experiments, AFP significantly decreased the P concentration in faeces (between 13 and 33%) as well as increased the growth rate and decreased the feed conversion ratio. Bone strength was significantly higher in the growing-fattening pigs fed on the AFP diet.
Simões Nunes
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Société Chimique Roche, Centre de recherche en nutrition animale (CRNA), Village-Neuf, France. carlos.simoes-nunes@roche.com
Guggenbuhl
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P
D010832:6-Phytase / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000097:blood; D000821:Animal Feed; D000818:Animals; D001232:Aspergillus fumigatus / Q000201:enzymology*; D015519:Bone Density; D002118:Calcium / Q000097:blood; D019587:Dietary Supplements; D004063:Digestion / Q000502:physiology*; D005243:Feces / Q000737:chemistry; D008297:Male; D010758:Phosphorus / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D013552:Swine / Q000502:physiology*
D010758:Phosphorus; D000469:Alkaline Phosphatase; D010832:6-Phytase; D002118:Calcium