Key amino acid considerations when using phytase If phytases have the same phosphorus release recommendation then the amino acid contribution should also be similar. 1. Matrix recommendations should be supported by a meta- analysis of large data-sets. 2. Amino acid release can be linked to phosphorus release curves and phytate destruction up to ~1000FYT. Above this level amino acid response is disproportionate relative to phosphorus release. 3. Matrix values for amino acids should always follow expected response patterns. Matrix values not reflecting this should be treated with caution. 4. Phytase amino acid response patterns are different for pigs than poultry. Identical matrix values for both species are therefore not acceptable. 5. Amino acid uplift values should be lower for pigs (1-4%) than for poultry (2-6%)


a clear difference between species, where the same value for broilers was 4.1%.


Species effect In other areas of the evaluation there were similarities between broilers and swine but also different trends concerning the effect of phytase. For example, the relationship between the destruction of dietary phytate and average ileal amino acid digestibility improvement is less clear in pigs. This has prompted the theory that phytate may be less of an anti-nutrient in pigs than it is in poultry. Mean responses to phytase on individual amino acids were


calculated (Figure 5). Both the pattern and magnitude of the responses were different to that seen in poultry. Broilers have a higher response in all amino acids other that tryptophan, glutamine, and proline.


Figure 5. Individual mean amino acid responses to phytase addition in pigs


3.5 3


2.5 2


1.5 1


0.5 0


Arg Lys His Leu Ile Met Thr Trp Phe Val Amino Acid


Phytase improved amino acid digestibility, supporting matrix values of 1-4% in swine.


The improvement in methionine digestibility is similar for both species. However, the effect on cysteine is much higher in broilers


PAGE 36 MAY/JUNE 2017 FEED COMPOUNDER Tyr Cys Ala Asp Glu Gly Ser Pro


than in pigs – as it is for serine plus glycine, valine and threonine. It is particularly interesting that the sulphur amino acid response in pigs is very low indeed (<1% for methionine plus cysteine), whereas in broilers it is over 3.5%. This overall trend is not fully understood but may be related to the fact that phytate has less of an effect on endogenous secretions in pigs than it does in poultry. The difference in uplift values for individual amino acids can be


seen in a comparison of the data from the two meta-analyses (Figure 6.). It is therefore wrong to simply extrapolate matrix value for pigs from those generated in poultry or vice versa.


Figure 6. Differences between the effect of phytase on amino acid digestibility, between poultry and pigs


7 6 5


3 4


0 1 2


0 Arg Cys Thr Val Ser His


Leu Lys


Tyr


Asp Ala


Phe Trp Glu Met 0.5 1 1.5 2 2.5 % change in ileal amino acid digestibility coefficient with phytase in pigs


There is weak correlation between the amino acid responses in broiler and those of pigs.


Conclusions The results of these meta-analyses offer clear evidence that phytase increases ileal amino acid digestibility in broilers and pigs. The review additionally demonstrates that there are differences between species and between amino acids. It also shows that it is inappropriate for different phytases with essentially equivalent phosphorus release recommendations, to have widely different amino acid recommendations. In both data sets it was seen that at higher doses, whilst phosphorus release continued to rise, that of amino acids flattened out. Such findings, from the analysis of large pools of data from a variety of sources, give a best estimate of the true value of phytase. This not only ensures creation of more reliable matrix values but also helps the end user better benchmark different phytases for value comparisons. It removes confusion and assists in setting the record straight on amino acid responses.


References Cowieson, A.J. et al. A systematic view on the effect of phytase on ileal amino acid digestibility in broilers. Animal Feed Science and Technology , Volume 225 , 182 - 194


Open access paper at ScienceDirect Cowieson, A.J. et al. A systematic view on the effect of phytase on ileal amino acid digestibility in pigs. Animal Feed Science and Technology. Under review


3 3.5 Pro Gly


Mean % improvement in digestibility with phytase


% change in ileal amino acid digestibility coefficient with phytase in broilers


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