Understanding variation in substrate levels and their properties is also a prerequisite to understanding synergies between phytase and other enzymes such as carbohydrase and protease. Positive results in terms of nutrient digestibility have been seen with phytase and xylanase application in wheat based diets with low, medium, or high lysine levels for growing pigs, suggesting that savings could be made on expensive protein addition through use of the enzyme combination18. Additional trials have also shown that combining xylanase and phytase in diets that have high arabinoxylan and phytate content (e.g. wheat middlings) can dramatically improve nutrient availability by reducing anti-nutrient levels and improving nutrient utilisation19. These findings have implications not only in terms of the additional cost savings that can be made by using them in combination, but in terms of the impact on animal gut health. Many production factors can impact the balance of the pig’s gut microflora, the type, amount and availability of undigested substrate is highly significant. In feed antibiotics have traditionally been used to overcome disease challenges in pigs20, but growing concerns about residues in meat products and potential bacterial resistance to antibiotics has led to increased research into practically feasible alternatives21. Given that combinations of enzymes have been shown to tackle various substrates in the diet and thereby reduce the possibility of microbial proliferation, it's possible that they could help replace the in-feed antibiotics, which have the same role. Production profitability should be ensured through continuing research into the impact of substrates, and the great difference that phytase and other enzymes can make to digestibility and performance by tackling their negative effects. AAF