Prophylactic intra muscular injection of Fe in young pigs may still be insufficient to prevent Fe deficiency. Super-dose of phytase would be expected to degrade even the lower esters of phytate and may improve performance through increase phytate bound-Fe bioavailability. A total of 234 pigs (7.6 + 0.16 kg BW) were weaned at ∼28 d of age and blocked into pens of 4 or 5 balanced for weight, sex, and litter origin. Dietary treatments were provided for 20 days in a 3 × 2 factorial design with 3 levels of phytase (0, 500 or 2500 FTU/kg feed) and 2 levels of Fe (50 [low; L-Fe] or 300 [high; H-Fe] mg/kg feed as FeSO4) on a wheat-SBM based diet. At the end of the experiment, 1 pig per pen was euthanized for blood, plasma, liver, and ileal digesta collection.
The dietary treatment L-Fe shown lower ADFI than the H-Fe diet. An interaction Fe x Phytase shown that phytase at 2500 FTU/kg improved ADG of pigs fed the L-Fe diet to a level comparable with H-Fe fed pigs. Nevertheless, this effect was diminished when added to the H-Fe diet. Reducing the dietary Fe level resulted in reductions in haemoglobin, haematocrit, Fe and ferritin in plasma, and liver Fe concentration. Furthermore, plasma transferrin was higher in pigs fed L- Fe diet. Additional phytase at 2500 FTU/kg tended to increase haematocrit concentration but had no influence on other measured indices of Fe status. There was an Fe x phytase interaction for ileal InsP6 degradation (P < 0.05), Which was similar than that observed for ADG. Phytase increased InsP6 hydrolysis to a greater extent when added to the L-Fe than the H-Fe diet (68.2 vs 30.8%).
Altogether, data indicates that high doses of phytase can effectively improve weaner pig performance under Fe-deficient diets. However, this benefit from high doses of phytase is reduced in Fe rich diets and further research to elucidate the effects of high doses of phytase on Fe bioavailability is required.
Laird, S., Kühn, I., and Miller, H. M. (2018). Super-dosing phytase improves the growth performance of weaner pigs fed a low iron diet. Animal Feed Science and Technology. 242:150-160. https://doi.org/10.1016/j.anifeedsci.2018.06.004