To Determine the Effect of Superdosing Phytase on Nursery Pig Performance, Zinc and Copper Blood Serum Levels When Fed Varying Levels of Copper Supplementation.

Dietary phytate is an anti-nutrient and phytase hydrolyses phytate improving mineral, energy and amino acid utilization. The objective of this trial was to determine the effect of copper sulphate supplementation on nursery pig performance, serum copper and zinc levels with or without superdosing phytase. A total of 720 weaned pigs (7 kg BW; D21) were randomly assigned to one of 8 dietary treatments (2 x 4 factorial) with 4 levels of supplementary copper; 15, 62.5, 125 and 250 ppm at 2 levels of phytase (Quantum Blue); 0 and 2000 FTU/kg. Each treatment consisted of 9 pen replicates with 10 pigs per pen (mixed sex) and were fed a 3 phase feeding program P1 (W-D7), P2 (D7–D21) and P3 (D21–D42). In P1 and P2 all diets were formulated to meet the pigs’ nutrient requirements (NRC, 2012) including adequate phosphorus. In P3, with phytase addition, diets were formulated at 0.15% and 0.16% below requirement for available P and calcium respectively. At D21 and D42 pigs were weighed and one pig per pen was selected for blood sampling. At D21 there was a linear ADG response (P < 0.05) to copper addition and an ADG improvement (P < 0.001) with phytase and no phytase x copper interaction in ADG was observed. In contrast, FCR showed an interaction with phytase superdosing improving performance at 15 and 125 ppm copper (P <0.05) with a numerical improvement at 62.5 ppm copper. At D21 there was no effect of copper on blood mineral levels, however with phytase addition there was a reduction (P < 0.02) of copper and an increase (P < 0.01) in zinc serum levels. At D42 there was no interaction between copper and phytase. Phytase superdosing improved liveweight (24.29 v 25.88; P < 0.05) and FCR (1.41 v 1.30; P< 0.05) at D42 irrespective of copper dose with copper addition resulting in a linear improvement in ADG (P < 0.05) and FCR (P < 0.02). At D42 copper did not affect zinc serum levels but did result in higher (P < 0.05) copper serum levels for 250 ppm compared to all other treatments. In summary, at D42 phytase improved ADG and FCR at all levels of copper supplementation while increasing copper to 250 ppm resulted in an improved nursery performance. Furthermore, performance was similar between pigs fed 250 ppm copper and pigs fed 62.5 ppm copper with phytase at 2000 FTU/kg