Interaction between Dietary Phytase, Calcium and Digestible Phosphorus Levels on Performance and Tibia Ash in Broilers
Published:June 12, 2013
Summary
I. INTRODUCTION The global availability of inorganic phosphates is limited; phosphorus (P) is the third most expensive ingredient after energy and amino acids. Therefore sustainable animal production requires optimal utilisation of P to reduce the cost of feeding. Over two thirds of P in plantbased feedstuffs is not readily available in poultry as it is bound to phytic acid (PA), which has be...
Excellent article that confirms a well known phenomena. However (at least to me) it is still not clear if the same thing happens with LAYERS or not, and also, if it also affects digestion and metabolism of other minerals such as zinc amongst others. A comment on this respect is of interest.
Overall tibia ash contents look too low. Probably the ash contents were calculated based on bone wet weight. Fat-free, dry weight basis is usually recommended to express bone ash content to reduce variations in the measurement.
Dear All,
Thank you for the interest. It is true that tibia ash is expressed on a wet weight basis, however the statistical significance does not change when converting to DM, for 36 d, treatments 1-8: 44.73, 44.64, 44.10, 43.81, 45.49, 43.24, 43.72, and 44.00 %.
Sergio, layer requirements are completely different so while you may observe the same interactions between phytase, dP, IP and Ca in the bird you cannot reduce Ca for obvious reasons. Nutreco has had success with split feeding in layers (you can consult Hifeed on this), and following this system you can offer limestone in a separate feed and this may allow for some reductions in inorganic phosphorus in the second feed you offer, as the availability of P from phytate will increase (using phytase will further improve this). Zn will form complexes with phytate, and actually phytate favour cation interaction with Zn, but due to low levels in the intestine it is not focused on so heavily.
Regards
Adam
Adam: Thanks for your response. Yes, I do agree with you, since my comment, i have encountered several articles in which the effect of ¨high¨calcium levels in layer feed, as you say, DO diminsh phytase efficacy and overall bone mineralization as related to phytase activity. Secondly, the comment regarding measurment of tibia ash is NOT mine but still i will make the following comment in asking for a commentary: It seems to me that some BONE QUALITY measurements perhaps should NOT be expressed (nor calculated)on a weight basis but on a VOLUMETRIC basis. My argument - correct me if I am wrong- is that bone structure is highly porous and therefore grinding and weighing eliminates or reduces the TRUE status of bone as affected by treatments. In order words what would have happened if bone paraneters ( tibia ash%) were expressed as cm3 instead of grams?
Hi Adam, here a couple of comments. I read the paper long time ago but never had chance to comment due to some issues with my internet connections. I am now recovering some of these I wanted to talk/ask. Adam, could it be the phytase you added - you don`t mention the source - was not that efficacious at low pH and that could have had an influence on the results? Could it also be the level of p-phytate was overestimated by you sinc the diet is purely corn-soya (probably low in PP). Many thanks from Spain. Rafa.
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