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Wheat and barley increase phytate degradation and phosphorus digestibility in corn fed to pigs
- Poulsen, H.D., Voergaard, A.L., Strathe, A.B., Blaabjerg, K.
- Animal feed science and technology 2019 v.248 pp. 77-84
- barley, corn, crates, diet, digestibility, enzyme activity, feces, half life, leukocytes, metabolism, phosphorus, phytases, phytic acid, soaking, swine, urine, wheat
- Two experiments evaluated the additivity of phytate content and coefficient of total tract apparent digestibility (CTTAD) of phosphorus (P) in wheat-barley (WB) and corn (C) when soaked (exp. 1) or fed dry to pigs (exp. 2) in combination with or without microbial phytase (1250 FTU/kg as-fed). In exp. 1, WB (1:1, w/w) and C were soaked separately or together (W:B:C = 1:1:2, w/w/w) without (WBC) or with microbial phytase (WBC + phy). Phytate content was affected by the interaction between diet and soaking time (P < 0.0001) as phytate decreased with time. The decrease was greatest for WBC + phy followed by WBC, WB and C resulting in a half-life of phytate (K) of 8.7, 15.8, 24.4 and 303.4 h, respectively. Soaking of WB and C together showed non-additive effects as the estimated (assuming additivity) phytate content at 2, 4, 8 and 24 h of soaking was 0.17, 0.34, 0.42 and 0.5 g/kg DM higher (P < 0.001) than the experimentally determined phytate content in WBC. Actually, phytate degradation in C was estimated to be 0.15, 0.30, 0.42 and 0.49 higher at 2, 4, 8 and 24 h, respectively, when soaked together with WB than when soaked alone. Accordingly, the estimated (assuming additivity) K-value for WBC was 148 h longer (P = 0.08) than the K-value derived from the experimentally determined phytate degradation in WBC. Exp. 2 comprised 24 pigs of 47 ± 2 kg from 6 litters. Pigs were housed in metabolism crates and fed one of four diets (WB, C, WBC or WBC + phy) for 12 days; 5 days adaptation and 7 days total collection of feces and urine. The CTTAD of P was greatest for WBC + phy followed by WB, WBC and C (P < 0.0001). Feeding WB and C in combination tended to show non-additive effects as the estimated (assuming additivity) CTTAD of P in WBC was 7.7 percentage units lower (P = 0.09) than the experimentally determined CTTAD of P in WBC. In fact, CTTAD of P in C was estimated to be 14.6 percentage units higher when fed together with WB than alone. In conclusion, phytases present in W and B are non-specific and catalyze the degradation of phytate in C when soaked or fed dry together (ratio 1:1:2). Thus, when phytate rich cereals very different in plant phytase activity, are mixed, additivity cannot be assumed.