الفهرس 
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Abstract
The experimental work of the present study was carried out at El-Takamoly Poultry project (TPP), Fayoum Governorate, Egypt, during the period from March to July 2014. This study was undertaken to assess the dietary effects of essential oil blend (EOB), mannan oligosaccharides (MOS) and their combination on the productive and reproductive performance, egg quality and blood parameters of Golden Montazah laying hens at late egg production period. A total number of 720 laying hens plus 72 males of Golden Montaza at 56 weeks of age were allocated randomly into six treatments groups (120 hens plus 12 males), each group was equally subdivided into three replicates (40 hens plus four males). Birds were distributed into 18 pens (40 hens and four males each) in such order to have a similar mean body weight and average daily egg production.
The dietary treatments used in this study were as follows:
1-Birds were fed the control diet (diet 1).
2- diet 1 + 200 mg prepared essential oil blend (PEO)/kg diet.
3-diet 1 + 100 mg commercial essential oil blend (CEO)/kg diet.
4-diet 1 + 500 mg MOS/kg diet.
5-diet 1+ 200 mg PEO + 500 mg MOS/kg diet.
6-diet 1 + 100 mg CEO + 500 mg MOS/kg diet.
Results obtained could be summarized in the following:
Laying hens fed diet containing 100 mg CEO + 500 mg MOS/kg diet had significantly higher values of egg production (EP%), live body weight change (LBWC) and the best feed conversion (FC), crude protein conversion (CPC) and caloric conversion ratio (CCR) during all significant periods studied, while, laying hens fed control diet had significantly lower values of EP%, LBWC and the worst FC, CPC and CCR during the same periods. No significant effect were observed for egg mass, feed intake, initial body weight, final body weight and mortality rate% during the experimental period.
There were insignificant differences among all dietary treatments in carcass characteristics except, spleen%. Laying hens fed diet containing 100 mg CEO +500 mg MOS/kg diet had higher spleen% whereas, those fed control diet had lower spleen% at the end of experimental period. Laying hens fed diet containing 100 mg CEO + 500 mg MOS/kg diet had significantly higher values of lactic acid bacteria count and the lower values of total count of bacteria and E-coli, while, those fed control diet had significantly higher values of total count of bacteria and E-coli and the lower values of lactic acid bacteria count.
There were insignificant differences among all dietary treatments in egg quality at 64 and 72 weeks, fertility and hatchability% at 64, 68 and 72 weeks. There were insignificant differences among all dietary treatments in chemical composition of eggs, except, cholesterol concentration in the yolk at 72 weeks. Laying hens fed diet containing 100 mg CEO +500 mg MOS/kg diet had significantly lower cholesterol in the yolk, whereas, those fed control diet had significantly higher cholesterol in the yolk at 72 weeks. No significant differences due to EOB and MOS supplementation on biochemical plasma parameters, except, total protein, globulin and calcium which were significantly affected, laying hens fed diet containing 100 mg CEO +500 mg MOS/kg diet had significant higher values of total protein, globulin and calcium, whereas, those fed control diet had significant lower values of these parameters. Neither EOB nor MOS had any significant effect on hematological parameters. Laying hens fed diet supplemented with 100 mg CEO +500 mg MOS/kg diet had significant higher values of HDL cholesterol, total antioxidant capacity and GSH-Px activity in plasma. While, those fed control diet had higher values of total lipid, triglycerides and LDL cholesterol in plasma. Laying hens fed diet supplemented with 100 mg CEO +500 mg MOS/kg diet had significant higher value of immune response to antibody titer of Avian Influenza virus (AIV). While, those fed control diet had significant lower value of AIV. No significant differences of Newcastle Disease Virus among treatment groups. Golden Montazah laying hens fed diet containing 100 mg CEO +500 mg MOS/kg diet gave the best economical and relative efficiency values during the period from 56 to 72 weeks.
In conclusion, the results of this study indicated that feeding Golden Montazah laying hens during the period from 56 to 72 weeks of age on diets containing 100 mg CEO +500 mg MOS/kg diet improved the productive and reproductive performance, relative economic efficiency values, increased stimulation of immune, HDL cholesterol, GSH-Px activity, total antioxidants activity in plasma and decreased cholesterol concentration in the egg yolk. This may lead to produce enriched eggs that are healthier for human consumption especially for those suffering from heart diseases.
Key words: Essential oils, mannan oligosaccharides, productive and reproductive performance, egg quality and immune response.