Enhanced E. coli phytase at 2500 FTU improved piglet performance in both animal and plant protein-based diets

The presence of phytate (inositol-6-phosphate, IP₆) and its lower degree phosphorylation (IP_X) esters have been reported to significantly reduce digestion and absorption of minerals and proteins in monogastric animals, even at low concentrations (Wilcock and Walk 2016). In vivo reduction of IP₆ and IP_x ester content through superdosing of enhanced Escherichia coli phytase consistently improved nutrient utilisation efficiency and growth performance of monogastric animals (Wilcock and Walk 2016). Moreover, as the pharmaceutical dose of zinc oxide in piglet diets interacted with phytate and other divalent minerals, supplementation of 2500 FTU/kg phytase improved performance in weaned pigs (Walk et al. 2013). However, there still is a perception in the pork industry that piglets will not respond to phytase superdosing when offered an animal protein-based diet with low phytate content. This study tested the hypothesis that enhanced E. coli phytase at 2500 FTU/kg will improve performance of piglets offered both animal protein (AP) and plant protein (PP)-based diets, containing low and moderate amounts of phytate, respectively.

A total of 1147 weaned piglets weighing 6.25 ± 0.16 kg (mean ± s.e., PrimeGro™ Genetics) were randomly stratified to a 2 × 2 factorial arrangement with the respective factors being diet type (animal or plant protein-based diet) and enhanced E. coli phytase (0 or 2500 FTU/kg; Quantum Blue^®, AB Vista). Each treatment consisted of 20 pen replicates (10 male, 10 female) with 14 or 15 pigs per pen. The experimental duration was 29 days after weaning with a three phase feeding system (Starter: 0 to 7 days, Weaner 1: 8 to 21 days, Weaner 2: 22 to 29 days). Phytase was supplemented over the top for the Starter and Weaner 1 diets, while a mineral matrix release from phytase (0.15% available phosphorous (P) and 0.16% calcium) was applied for the Weaner 2 diets. Starter, Weaner 1, and Weaner 2 diets were formulated to contain 14.9, 14.8 and 14.4 MJ digestible energy (DE)/kg, respectively and 0.9 g standardised ileal digestible lysine/MJ DE for all three-phase diets. Animal protein diets included meat and bone meal, fish meal and blood meal which were partly or entirely replaced by soybean meal and lupins in PP diets. For Starter, Weaner 1, and Weaner 2 diets, the calculated phytate-P contents in AP diets were 0.16, 0.20, and 0.23%, while phytate-P contents in PP diets were 0.20, 0.25, and 0.28%, respectively. Piglets had ad libitum access to the respective pelleted diets and fresh water throughout the experiment. Average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR) were measured (Table 1). Data were subjected to two-way analysis of variance using JMP statistical software (SAS JMP pro v13.1, SAS Institute Inc., Cary, NC, USA).

Table 1.  Effect of diet type and 2500 FTU/kg phytase on performance of weaned pigs

The hypothesis tested in this study was supported. Inferior performance of AP diets compared to PP diets may be due to amino acid shortfall in AP used. Piglets fed PP diets and 2500 FTU phytase significantly improved ADG (P < 0.001) due to increased ADFI (P < 0.05) with a better FCR (P < 0.001). There was an interaction between diet type and phytase for FCR such that the improvement was greater in piglets fed AP-based diets (P < 0.05). However, lack of interaction between diet type and phytase for ADG and ADFI indicates that 2500 FTU phytase can reduce anti-nutritional effects of phytate even at low dietary phytate levels, especially in diets formulated based on AP.