In a paper published recently in the journal, Poultry Science, C.Q. Gao and colleagues at China Agricultural University in Beijing explain that they conducted three experiments to evaluate the compositional and nutritional values of corn grains – phytase transgenic corn; PTC) and isogenic conventional corn (CC) – and compare the efficacy of corn–based phytase and extraneous microbial phytase for enhancing the utilisation of phytate phosphorus (P) in single corn or corn-soybean mixed meals (corn:soybean = 2.5:1 by weight) fed to roosters.

Following a 48–hour fasting period, 16 roosters were given 50g of each sample via crop intubation and excreta were collected for 48 hours. Nitrogen–free and phosphorus–free diets were used to evaluate endogenous amino acid and endogenous phosphorus losses, respectively. Chemical composition was not different between PTC and CC, whereas the phytase content for PTC was greater than CC (8,047 versus 37FTU per kg of corn, DM basis; P<0.001).

No difference was observed in the TME and true amino acid availability values between the PTC and CC in roosters.

The true phosphorus utilisation for PTC was greater than CC (37.92 versus 55.85 per cent; P<0.001), and CC and PTC contained 0.13 and 0.19 per cent available phosphorus (AP, DM basis; P<0.001), respectively. There was no difference in P utilisation (72.76 versus 70.23 per cent; P>0.05) between roosters fed PTC and extraneous microbial phytase in equivalent FTU per kg of diets.

The results of this study indicated that the chemical composition, TME and true amino acid availability in PTC are essentially equivalent to that in CC, and the true phosphorus utilisation for roosters is higher in PTC than in CC. Corn expressing phytase is as efficacious as equivalent microbial phytase when supplemented in corn-soybean diets for chickens.

Reference

Gao C.Q., Q.G. Ma, C. Ji, X.G. Luo, H.F. Tang and Y.M. Wei. 2012. Evaluation of the compositional and nutritional values of phytase transgenic corn to conventional corn in roosters. Poult. Sci. 91(5): 1142-1148. doi: 10.3382/ps.2011-01915

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