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Afrin, S, 2023. Improving the efficacy of phytase in poultry diets. PhD, Nottingham Trent University.
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Abstract
Global poultry production faces several challenges, among which ensuring the maximum utilisation of nutrients from plant-based feed materials is gaining importance. Phytate is a major storage form of plant phosphorus (P) which is considered an antinutritional factor due to its adverse effect not only on the utilisation of plant P by poultry, but also other key nutrients. Therefore, it is vital to maximise the efficacy of phytase enzymes in poultry diets to not only release P and other dietary nutrients for use by poultry but also to reduce the use of finite mineral phosphate reserves in feed.
Phytase enzymes have been used for around 3 decades in poultry feed in moderate doses to improve the phytate P utilization to reduce the antinutritional effect of phytate by hydrolysing phytate, but more recently, it has been reported that further increasing the phytase dose (‘superdosing’) further improves broiler performance. The mechanisms by which phytase superdoses elicit additional performance improvements are not fully understood. Therefore, several factors relating to digestive efficiency need to be explored to get a better understanding of the mechanisms in play to improve digestive efficiency. These factors include how susceptible phytate within feed ingredients is to degradation by phytase and the effects of processing on phytase activity in finished feed. In addition, the use of novel feed ingredients with high mature grain phytase activity as an alternative to external phytase enzymes to improve poultry performance may employ further unexplored mechanisms. Thus, the overarching aim of the present project was to examine the different approaches including superdosing and use of novel feed materials along with other potential factors to improve the efficacy of phytase in poultry diet.
Two broiler trials were carried out alongside a number of in vitro studies to investigate different avenues for improving phytase efficacy in poultry diets. The first broiler trial investigated the the effect of super-dosing phytase supplementation on performance, whole body phosphorus (WBP) content and gut health of broilers. Though superdosing of phytase in broiler diets increased the generation of myo-inositol content in gizzard at day 7 and ileum and jejunum at day 21 and 35 through improved phytate degradation, this did not translate to any benefit on performance of broiler compared to other diets. Also, while improved tibia ash percentage has been commonly reported with superdosing of phytase, in this study, the tibia and whole-body Ca and P content were not affected. Interestingly, the WBP to tibia P ratio in broilers was not consistent across the ages assessed, which may indicate that tibia P is not an ideal estimate of WBP content. Finally, from this study, there was no effect of phytase superdosing on caecal microbial diversity compared to other diets, which indicates there is little effect of superdosing on gut microbiome.
The second bird study was conducted to determine the amino acid digestibility of a novel strain of HIGHPHY wheat for broilers. The coefficients of digestibility of some of the essential amino acids (threonine, valine, Isoleucine, leucine, lysine, and histidine) and P digestibility were all higher in HIGHPHY Wheat, suggesting the novel wheat may be a viable alternative to standard wheat not only in terms of improving P but also amino acid digestibility. An additional in vitro investigation indicated that phytase activity levels of nearly 58% were retained after pelleting HIGHPHY wheat. While the cost of using HIGHPHY wheat in place of standard wheat with additional phytase is likely too high for broad application, HIGHPHY wheat may have value in formulations of organic feed for poultry. From the in vitro studies, the key finding was that, for all feed ingredients obtained from different countries of origin, there was huge variation in susceptible phytate values between samples of each ingredient, but overall, it was concluded that the common industry practice of assuming just 35% of dietary phytate from all feed ingredients is hydrolysed by phytase is an underestimate.
To conclude, the findings of the present investigation provide better understanding of the potential mechanisms associated with superdosing phytase in broiler diets. Determination of WBP content is very laborious but future studies are needed to quantify the WBP content together with P digestibility to provide a more complete picture of the P retention in broilers. Also, it would be more precise to formulate diets by taking into consideration the susceptible phytate level of the batches of ingredients present in that particular diet. This would give a more accurate level of plant-derived P available to the bird and reduce the need for excess inorganic P addition. Application of these findings to commercial practice would further improve the environmental sustainability of global broiler production.
| Item Type: | Thesis |
|---|---|
| Creators: | Afrin, S. |
| Contributors: | Name Role NTU ID ORCID |
| Date: | January 2023 |
| Rights: | This work is the intellectual property of the author, Sumaiya Afrin. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed in the owner(s) of the Intellectual Property Rights. |
| Divisions: | Schools > School of Animal, Rural and Environmental Sciences |
| Record created by: | Laura Ward |
| Date Added: | 15 Jul 2024 14:01 |
| Last Modified: | 15 Jul 2024 14:04 |
| URI: | https://irep.ntu.ac.uk/id/eprint/51759 |
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