Format: MS WORD Chapters: 1-5
Pages: 68 Attributes: COMPREHENSIVE RESEARCH
1.1 BACKGROUND OF THE STUDY
Most of the feed ingredients used in formulation of poultry diets are mainly of plant origin especially Maize and Soy Bean which are the major feedstuffs used. Approximately two-thirds of the phosphorus in these ingredients form complexes with the phytic acid (or phytate) molecule, which prevents their use (Cabuk et al., 2004). The excretion of nitrogen (N) originating from dietary protein is largely responsible for the environmental issues arisen from intensive livestock production (Morse, 1995).
Phosphorus (P) in phytic acid form is poorly available to monogastric animals, due to the lack of phytase in their digestive tracts (Cabuk et al., 2004). The low bioavailability of P in plant ingredients poses problems both economically and environmentally. After energy and protein, phosphorus(P) is the most expensive component in a poultry diet.
This fact implies addition of inorganic phosphorus to the diets, originating from non-renewable sources in the nature, to meet the bird requirements of this mineral. As a result, the feed becomes costlier and birds eliminate larger amounts of phosphorus in their excreta. The phytase enzyme produced by Aspergillus niger has been successfully used in poultry and swine diets to release part of the complexed phosphorus in the form of phytate; improve the nutrient digestibility; and consequently excrete less phosphorus into the environment (Selle et al., 2009, Gomide et al., 2011a, Selle et al., 2012).
Phytase is commonly supplemented in laying hen diets to improve phytate phosphorus (P) availability and retention and ultimately to reduce excretion (Ravindran et al., 2000, Jalal and Scheideler, 2001, Gao et al., 2013, Gosh et al., 2015). Phytate is the main phosphorus source in the plant-based feed ingredients, which not only has limited availability to laying hens, but can also reduce the availability of other nutrients. Phytate can complex with amino acids (Ravindran et al., 2000, Rutherfurd et al., 2004), starch and fat (Ravindran et al., 2001, Newkirk and Classen, 2001), thus reducing the absorption of these nutrients. In addition, phytate can interact with endogenous enzymes and result in a negative impact on sodium (Na) and amino acid (AA) digestion and increase endogenous AA losses. Furthermore, in the intestine, phytate binds to calcium (Ca) and other minerals, forming insoluble salts and rendering these minerals unavailable for absorption.
Phytase enzymes have the ability to hydrolyse phytate, releasing P which reduces the formation of phytate mineral complexes, increasing the bioavailability of minerals (Kornegay et al., 1996, Jalal and Scheideler, 2001). In addition to the P and Ca release, inclusion of phytase in the diet may reduce the negative impact of phytate on AA and starch digestion, improving digestibility of dietary AA and energy
Phytase supplementation improves the availability of nutrients such as protein and amino acids (Ravindran et al., 2000, Rutherfurd et al., 2004) and energy (Kornegay et al., 1996, Namkung and Leeson, 1999, Ravindran et al., 2000, 2001, Newkirk and Classen, 2001, Hughes et al., 2009) in poultry.
In laying hen diets phytase is traditionally supplemented at 300 FTU/ kg although recent studies showed that increased phytase dose in laying hens diets can further increase phytate P degradation, ileal P digestibility and reduce P excretion (White et al., 2016).
Most of the phosphorus in plant is in phytic acid form which is poorly available to poultry, because poultry lack endogenous phytases that are able to degrade phytate effectively. Therefore, a large proportion of dietary P cannot be utilized and is excreted in the faeces. Improving the availability of phytate P would reduce the necessity to include feed phosphates in the diet and enable a reduction of the dietary P content and increase availability of other nutrients (Rutherfurd et al., 2004.) hence reducing cost of feed and increasing productivity of the animal.
1.3 STATEMENT OF RESEARCH PROBLEM
During the last 10 years there has been an escalating usage of microbial phytase in pig and poultry diets. Compared to broiler chicks, phytase inclusion in diets for laying hens has been the subject of less research. In laying hens, most of published studies on phytase have focused on phosphorus utilization and the reports of phytase on utilization of dietary crude protein by laying hens are inconsistent, hence the need for this study.
1.4 OBJECTIVE OF THE STUDY
The objective of this study was to determine the effect of phytase supplementation on the performance and egg characteristics of laying hens fed diets with different levels of crude protein
1.5 RESEARCH QUESTIONS
Does phytase supplementation have effect on the performance of laying hens fed diets with different levels of crude protein?
Does phytase supplementation have effect on egg characteristics of laying hens fed diets with different levels of crude protein?
1.6 RESEARCH HYPOTHESES
Phytase does not have significant effect on performance of laying hens fed diets with different levels of crude protein
Phytase does not have significant effect on egg characteristics of laying hens fed diets with different levels of crude protein
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