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Improving nutrient utilization through the use of super-dosing of phytase in growing pig diets
Previous research has provided evidence that super-dosing phytase may improve pig performance through so-called ‘nutrient uplift.’ This experiment was conducted to investigate this possibility by determining if super-dosing of phytase improves the apparent total tract digestibility (ATTD) of energy, nitrogen and dry matter. Thirty-two pigs were placed on test at an average initial body weight of 39.7 ± 0.69 kg, after being blocked by initial body weight. Diets were fed in 3 phases and were based on corn and soybean meal with chromic oxide added at 0.4% as an indigestible marker. There were 4 treatments containing increasing levels of Quantum Blue® phytase. A control diet contained 250 FTUs of phytase/kg diet which released the equivalent of 0.08% STTD phosphorus from phytate; to this base diet, 3 super-dose levels were added above that of the control: 1000 FTUs, 1750 FTUs, and 2500 FTUs. Pigs were fed at 3.2 times maintenance and water was provided ad libitum. Feces and urine were collected at 40, 60 and 80 kg, respectively. Samples were analyzed for gross energy, dry matter, nitrogen, and chromic oxide. Data were analyzed using the MIXED procedure of SAS (9.4) with treatment and collection weight being fixed effects, and weight block as a random effect. ATTD of GE was not affected by phytase level: 89.0%, 88.2%, 89.2% and 89.2% for the control, 1000 FTU, 1750 FTU and 2500 FTU treatments respectively (P=0.1345). ATTD of DM was not affected by phytase level: 90.1%, 89.6%, 90.5% and 90.6% for the control, 1000 FTU, 1750 FTU and 2500 FTU treatments respectively (P=0.1533). Similarly, ATTD of N was not affected by phytase level (P=0.6181). Overall, ATTD of CP was higher at 40 kg compared to 60 kg and 80 kg (90.3% vs 89.1%, and 89.3% respectively, P < 0.01). ATTD of GE was lower at 60 kg than 40 kg or 80 kg (88.6% vs 89.0%, and 89.2%, respectively, P = 0.04), and ATTD of DM was lower at 60 kg than 40 kg or 80 kg (89.9% vs 90.2%, and 90.6%, respectively, P = 0.04). In conclusion, under the conditions of this study, no evidence was observed to suggest that super-dosing of phytase provided a benefit in terms of ATTD of energy, CP or dry matter.
Keywords: phytase, superdose, digestiblity