Insoluble dietary fiber does not affect the ability of phytase to release phosphorus from phytate in the diet of nursery pigs1

Abstract

Phytase is added to swine diets to improve the utilization of phytate-bound P in swine diets. This provides financial and environmental benefits to the pig industry. However, it is unclear if phytase works equally well in all dietary circumstances. The objective of this experiment was to determine if insoluble fiber affects the efficacy of the phytase enzyme in nursery pigs when fed diets limiting in P content. A total of 480 pigs (initial BW 5.48 ± 0.14 kg) were blocked by BW and randomly assigned (10 pigs per pen) to treatment within the block. A common nutrient-adequate diet was fed from days −14 to −5, and two basal P deficient diets (either a corn-soy diet containing 0.16% standardized total tract digestible [STTD] P [low insoluble fiber [LF]], or a corn-soybean meal plus 20% corn bran containing 0.14% STTD P [high insoluble fiber [HF]]) were fed from days −5 to 0 to acclimate pigs to a P deficient diet. From days 0 to 21, pigs received eight dietary treatments (six pens per treatment: n = 6). Experimental diets consisted of LF supplemented with one of four levels of added phytase (0, 109, 218, and 327 phytase units [FTU]/kg; Quantum Blue 5 G, AB Vista, Wiltshire, United Kingdom) expected to provide 0.16, 0.21, 0.26, and 0.31% STTD P, respectively, or HF supplemented with one of the same four levels of added phytase expected to provide 0.14, 0.19, 0.24, and 0.29% STTD P. Titanium dioxide was added to the diet at 0.4% as an indigestible marker. On day 21, one pig representing the average BW for each pen was euthanized, and fibulae were collected and analyzed for bone ash. Fecal samples were collected from each pen on days 19–20. Data were analyzed using PROC MIXED of SAS. There were no interactions between insoluble fiber and phytase for any of the variables evaluated. For days 0–21, adding phytase increased ADG (P < 0.001) with the response being linear (P < 0.001), whereas insoluble fiber decreased ADG (P = 0.033). There were no effects of phytase or insoluble fiber on ADFI (P = 0.381 and P = 0.632, respectively). Phytase improved G:F ratio (P < 0.001) with the response being linear (P < 0.001). Insoluble fiber tended to decrease G:F ratio (P = 0.097). Phytase increased bone ash (P = 0.005) with the response being linear (P = 0.001), but there was no effect of insoluble fiber (P = 0.949). Phytase did not affect the apparent total tract digestibility of DM, NDF, or ADF (P > 0.050), whereas insoluble fiber decreased the ATTD of DM (P < 0.001), NDF (P < 0.001), and ADF (P < 0.001). In conclusion, the addition of insoluble fiber did not affect the ability of phytase to improve growth performance and bone mineralization in nursery pigs fed a P deficient diet.

A comparison of the release of phosphorus by a phytase enzyme in pigs fed diets deficient or adequate in phosphorus content

“…The lack of diet × phytase interaction indicates that there was no difference in the ability of phytase to improve the digestibility of DM, GE, or CP in P-AD diets vs. P-DE diets. Some studies have suggested that quite high levels of phytase are required to see effects on the digestibility of nutrients other than P and Ca ( Zeng et al, 2016 ; Acosta and Patience, 2019 ).…”

“…The resulting daily P intake remained above requirement ( NRC, 2012 ), so this target was met. The level of P in the P-DE diet was chosen based on previous experience ( Olsen et al, 2018 ; Acosta and Patience, 2019 ) to achieve sufficient impairment of P intake to achieve experimental objectives while avoiding pressure placed on animal well-being due to impaired skeletal development. Previously published researches seeking to achieve similar objectives were also consulted ( Jones et al, 2010 ; Kerr et al, 2010 ; Kühn and Partanen, 2012 ; Taylor et al, 2016 ; Vier et al, 2019 ).…”

The impact of specialty protein ingredients on the growth performance and health of nursery pigs

“…The enzyme blends typically include proteases and carbohydrases (such as α-galactosidase or sucrase), but may also include phytase . Phytate is the main storage form of phosphorus in grains and oil seeds, but it cannot be utilized by pigs as they lack the endogenous form of phytase needed to digest the phytate (Acosta and Patience, 2019). Therefore, treatment of ESBM with exogenous phytase can increase phosphorus digestibility in the resulting product .…”