Application of a phytase energy and nutrient matrix to a mixed-cereal diet maintained growth performance and reduced feed costs and reduced carbon foot print of production in weaned pigs

Abstract The effect of applying two levels of net energy (NE) reduction to a nutrient-reduced, mixed-cereal diet supplemented with two levels of a consensus bacterial 6-phytase variant (PhyG) was evaluated in weaned pigs. In total, 360 TN70 × Tempo (Greater York × Norsvin Landrace) weaned pigs (8.40 ± 0.78 kg) were assigned to 60 floor pens (five treatments, 12 pens/treatment, six pigs/pen) in a randomised complete block design. Diets were formulated in two phases (day 0 to 14 and day 14 to 35) and fed ad libitum in pelleted form. Treatments comprised a nutritionally adequate mixed-cereal positive control (PC) and four negative control (NC) diets. The NC diets were reduced in digestible P, Ca, digestible amino acids (AA) and Na according to the matrix for PhyG added at 1,000 phytase units (FTU)/kg or 2,000 FTU/kg. Each NC was formulated with low (L) or high (H) NE reduction vs PC ((for 0-14 days/14-35 days) L-58/53 or L-65/58 kcal/kg, H-78/73 or H-86/80 kcal/kg with PhyG at 1,000 and 2,000 FTU/kg, respectively). The NC diets were not tested alone without supplementation on ethical grounds. Pigs fed PC had a final body weight (BW) of 23.1 ± 2.0 kg and overall feed conversion ratio (FCR) of 1.34. Pigs fed PhyG-supplemented, NE and nutrient-reduced diets had final BW, average daily gain (ADG), average daily feed intake (ADFI) and FCR responses not different from to or better than the PC group, per phase and overall. Estimated feed costs and carbon footprint (CFP) per kg BW gain (BWG) were lower in PhyG-supplemented treatments vs PC; lowest feed cost for L-NE reduction and PhyG at 2,000 FTU/kg (–5.5% vs PC). The data confirmed that PhyG supplementation could maintain growth per-formance at a reduced feed cost and CFP.