Super-dosing Phytase and Phytogenic Feed Additives to Improve the Performance and Health Status of Young Pig

The present thesis evaluated independently the effects of super-dosing phytase and phytogenic feed additives in weaned pigs. The first two experiments (Chapter II) determined 1) the optimal level of phytase (0, 1,250, 2,500, 3,750 FTU/kg) in diets with low (15.5 - 19%) and high (25 - 29%) inclusion levels of SBM (soybean meal) in healthy weaned pigs (102 pens and 2,550 pigs); and 2) the impact of low (15 -20%), medium (22.5 - 27.5%) and high (30 -- 35%) levels of SBM in diets with phytase (0 and 2,500 FTU/kg) in weaned pigs originating from a PRRS (porcine respiratory and reproductive syndrome)-positive sow farm (96 pens and 2,112 pigs). In experiment 1, high SBM improved daily gain and feed efficiency. Phytase supplementation improved feed efficiency regardless of the SBM inclusion level and this response was optimal at 2,500 FTU/kg. In experiment 2, increasing levels of SBM decreased the number of pigs that received medical treatments, but did not affect growth performance. The third experiment (Chapter III) evaluated the impact of inositol (0, 0.15 and 0.30%) and super-dosing phytase (0 and 2,500 FTU/kg) on growth performance and blood metabolites of nursery pigs (102 pens and 2,112 pigs). Super-dosing phytase improved daily gain. Supplementation of inositol improved feed efficiency in pigs fed diets without phytase to the same extent as pigs fed super-dosing phytase. Super-dosing phytase increased serum levels of Zn and Cu and plasma inositol, but reduced serum Fe These studies suggest that high SBM levels did not decrease performance and may be favorable in pigs originating from PRRS positive farms by reducing the cost of medical treatments. Effects of super-dosing phytase could be linked to the complete degradation of phytate and inositol production. The next three experiments (Chapter IV) evaluated the potential anti-bacterial effects of essential oils (EO) and esterified short- and medium-chain fatty acids (EFA) to improve the health status and performance of weaned pigs. In experiment 1, MIC (minimum inhibitory concentration) synergy tests determined the in-vitro susceptibility of Escherichia coli F4 and F18 to 2 blends of EO (EO1: garlic-derived allyl disulfide + d-limonene; EO2: garlic-derived allyl disulfide + gamma-terpinene + EO from the Myrtaceae family); and 3 mixtures of EFA (EFA1: monolaurin enriched + C4 to C12 mixture; EFA2: monobutyrin enriched + C4 to C12 mixture; EFA3: monobutyrin). Synergistic effects were observed for: EO1 with EFA1; EO2 with EFA1; and EO2 with EFA2 against both strains. In experiment 2, a double choice preference evaluated preference of nursery pig for diets containing EO2, EFA1, and EFA2. Each pen (n=48; 1 pig per pen) contained two identical feeders positioned side by side. One feeder contained a control diet and the other a control or test diet resulting in 4 possible comparisons: A: control vs. control; B: control vs. control + EO2; C: control vs. control + EO2 + EFA1; D: control vs. control + EO2 + EFA2. The inclusion rate of EO2, EFA1 and EFA2 was 0.1% for each. Results indicated strong aversion to diets containing EO2, EFA1, and EFA2. Experiment 3 determined the effect of EO2 and EFA1 on performance and immune response of weaned pigs (60 pens and 600 pigs) housed under a non-sanitary environment. Gain and feed intake decreased when pigs were supplemented with EO2 and with increasing levels of EFA1. Supplementation of EO2 reduced the serum levels of IL-4 and IL-10. In conclusion, in-vitro test suggested a potent synergy between EO and EFA against Escherichia coli strains F4 and F18. Under high antigenic challenge conditions, the supplementation of EO2 and EFA1 did not have a synergistic impact on the performance or serum cytokine concentrations of weanling pigs.