Supplementing increasing levels of 6-phytase improves mineral digestibility and restores performance in growing-finishing pigs fed nutrient- and energy-restricted diets

Context Phytase hydrolyses phytate, enhancing nutrient absorption, reducing feed costs, and minimising pollutants by improving mineral, amino acid, and carbohydrate availability, optimising energy use in pig nutrition. Aims Assess the effects of increasing 6-phytase concentrations in nutrient- and energy-reduced diets for growing and finishing pigs on performance, faecal excretion, nutrients and energy digestibility, blood metabolites, bone, carcass and meat traits. Methods Forty-two pigs (24.93 ± 1.67 kg) were assigned in randomised blocks to one of the following six treatments: positive control (PC) with nutritional requirements met and without phytase, negative control (NC) with reduced nutritional requirements and without phytase, NC + 500, 1000, 1500, or 2000 phytase units (FTU)/kg diet. Nutritional program was divided into the following four phases and fed for 89 days: Growing I (Days 0–27), Growing II (Days 27–42), Finishing I (Day 42–64), and Finishing II (Days 64–89). Key results Pigs fed NC had worse feed conversion than did those fed NC500, NC1000, and NC2000 during the total period, with an optimal phytase concentration of 1261 FTU/kg. Growing pigs fed PC had higher faecal calcium (Ca), whereas faecal phosphorus (P) was higher with PC or NC than phytase-supplemented diets. Faecal Ca and P, and digestible energy decreased linearly, whereas faecal gross energy and digestible Ca increased linearly. Apparent digestibility coefficients (ADC) of nutrients showed quadratic effects. Finishing pigs fed PC had higher faecal Ca and P, whereas NC-fed pigs had higher values than did those fed phytase-supplemented diets. Faecal Ca, P and zinc (Zn) decreased linearly, whereas Ca, P and Zn ADC and digestible minerals increased linearly. Blood P concentration was higher with PC or NC500 than NC or NC1500. Pigs fed NC had reduced loin depth than PC, NC1000 or NC1500, with an optimal phytase level of 1174 FTU/kg. Conclusions Increasing dietary 6-phytase concentrations enhances nutrient digestibility, reduces mineral excretion, and slightly improves meat traits. Under the conditions of this study, a 1000 FTU/kg dosage is adequate to restore growth performance in growing-finishing pigs. Implications This research provides new information on the effects of increasing 6-phytase concentrations in diets for growing and finishing pigs and supports its potential use to improve mineral digestibility, reduce mineral excretion, and contribute to more sustainable pig production.