The yeast production system in which Escherichia coli phytase is expressed may affect growth performance, bone ash, and nutrient use in broiler chicks

Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.

The efficacy of three Escherichia coli-derived phytase preparations on the performance and nutrient utilization of broiler chicks was evaluated. Two hundred sixteen 7-d-old male broiler chicks were grouped by weight into 6 blocks of 6 cages with 6 birds per cage. Six corn-soybean meal-based diets were randomly assigned to cages within each block. The 6 diets were adequate P, very low P, and low P and contained (g of P/kg of diet) 7.7, 4.0, and 5.1, respectively; and low-P diet plus phytase preparation A, B, or C at 1,000 units/kg of feed. All 3 phytase preparations were produced in different yeast production systems with slightly different glycosylation patterns. Preparation A was produced in Pichia pastoris, B in Schizosaccharomyces pombe, and C in Saccharomyces cerevisiae. The chicks were fed the experimental diets from 8 to 22 d of age. Excreta samples were collected between 17 and 21 d of age. At the end of the study, blood was collected, chicks were killed, and tibiae were removed from 3 birds per cage. Weight gain, feed intake, and feed efficiency among the 3 phytase preparations did not differ, although only phytase A diet outperformed (P < 0.05) the low-P diet in terms of weight gain and feed efficiency. All 3 phytase diets outperformed (P < 0.05) the low-P diet in bone mineral content, density, strength, percentage ash, P retention, and serum P levels. Phytase B diet outperformed the adequate-P diet in bone strength. All 3 preparations increased (P < 0.05) Ca retention with phytase B or C showing a better retention of Ca than phytase A. All 3 phytase preparations showed similar P use as indicated by BW gain and tibia bone characteristics.

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