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The objective of this study was to evaluate the effect of microbial phytase (1250 FTU/kg diet with 88% dry matter (DM)) on apparent total tract digestibility (ATTD) of phosphorus (P) in pigs fed a dry or soaked diet. Twenty-four female pigs (65 ± 3 kg) Landrace x Yorkshire x Duroc were used. Pigs were housed in metabolism crates and fed one of four diets for 12 days; 5 days for adaptation and 7 days for total collection of feces and urine. The pigs of dry diets were fed 1 kg and pigs of liquid diet were fed 3 kg (water-to-feed ratio: 2:1 (w/w)), twice a day. The basal diet was composed of wheat, barley, maize, soybean meal and no mineral phosphate. Dietary treatments were: basal dry-fed diet (BDD), BDD with microbial phytase (BDD +phy), BDD soaked for 24 h at 20°C before feeding (BDS) and BDS with microbial phytase (BDS +phy).
Supplementation of microbial phytase increased ATTD of DM and crude protein (N × 6.25) by 2 and 3 percentage units (P<0.0001; P<0.001), respectively. The ATTD of P was affected by the interaction between microbial phytase and soaking (P = 0.02). This was due to a greater increase in ATTD of P by soaking of the diet containing solely plant phytase compared with the diet supplemented with microbial phytase: 35%, 65%, 44% and 68% for BDD, BDD +phy, BSD and BSD +phy, respectively. The analyzed phytase activity of basal dry-fed diet (BDD)+phy was 21% higher than planned. Soaking for 24 h decreased the phytase activity with 340 FTU/kg DM (87%) in basal diet soaked for 24 h at 20°C (BDS) and with 570 FTU/kg DM (26%) in BDS+phy. The higher ATTD of P for BDS compared with BDD resulted from the degradation of 54% of the phytate in BDS by wheat and barley phytases during soaking. On the other hand, soaking of BDS +phy did not increase ATTD of P significantly compared with BDD +phy despite that 76% of the phytate in BDS + phy was degraded before feeding.
It is concluded that the addition of microbial phytase increased ATTD of P from 35 to 65% in the dry-fed diet. The effect of soaking of the diet without or with microbial phytase increased ATTD of P from 35% to 44% or from 65% to 68%, respectively. Consequently, soaking diet containing solely plant phytase provides a great potential for increasing ATTD of P. In contrast, soaking diet supplemented with 1250 FTU/kg diet does not increase ATTD of P significantly above the level obtained when the diet is fed dry. This is most likely because soaking with microbial phytase did not result in complete degradation of phytate before feeding, probably due to poor access of phytase to phytate in barley and wheat.
Blaabjerg, K., Thomassen, A.-M. and Poulsen, H. D. 2015. Microbial phytase addition resulted in a greater increase in phosphorus digestibility in dry-fed compared with liquid-fed non-heat-treated wheat–barley–maize diets for pigs. Animal, 9:2, 243–248. doi:10.1017/S1751731114002298.
