The effect of superdosing phytase on inositol and phytate concentration in the gastrointestinal tract and its effect on pig performance

Abstract Text: Dietary phytate has been shown to be detrimental to piglet performance and the use of superdosing levels of phytase can improve performance through phytate destruction rather than phosphorus provision. This extra phosphoric effect of superdosing phytase has not been widely tested in older pigs and therefore this trial was conducted to determine if increasing phytase (Quantum Blue) levels would improve performance in grower pigs (22.8 to 56.5 kg). In addition, inositol and phytate (IP6) levels were measured in the stomach and duodenum to determine if these were correlated to phytase dose and performance. Pigs (n = 300) were allocated to one of 5 treatments (5 pigs per pen and 12 replicate pens per treatment), T1, commercial diet formulated to meet the pigs nutrient requirements, except AVP and Ca were reduced 0.15% and 0.16% (equivalent of 500 FTU/kg phytase matrix), respectively, T2 was T1 with the addition of 500 FTU/kg phytase to target an AVP (0.32%) and Ca (0.71%) adequate diet, T3, T4 and T5 were T1 with, 1,000, 1,500 and 2,000 FTU/kg phytase, respectively. All pigs were fed a 2 phase feed program (0-21 d and 21-35 d) with gain, feed intake and FCR determined for the complete feeding period. At 35 d, 6 pigs per treatment of average BW were selected, penned individually and fed twice per day with the same treatment feed as previously fed. At 42 d each pig was fed 1.5 kg for 30 minutes and after an additional 60 minutes pigs were slaughtered and stomach and duodenum contents were removed for phytate and inositol analyses. There was a linear increase in ADG (P < 0.01) and ADFI (P < 0.01) and a linear improvement in FCR (P < 0.01) as phytase dose increased. There was a linear increase in inositol (P < 0.01) in the stomach/duodenum and a quadratic (P < 0.01) decrease in IP6 with increasing levels of dietary phytase. There is a good relationship between gastrointestinal phytate breakdown (R² = 0.95), inositol production (R²= 0.93) and FCR improvement. In conclusion supplementing grower diets with dietary phytase to doses exceeding commercial levels (> 500 FTU/kg) linearly improved performance (T1, 51.8 kg; T2, 54.5 kg; T3, 55.1 kg; T4, 55.7 kg; T5, 56.5 kg) and feed conversion (T1, 2.07; T2, 1.95; T3, 1.94; T4, 1.89; T5, 1.88) which may be linked to IP6 breakdown and inositol production in the gastrointestinal tract.

Keywords: Phytase Phytate Pig