الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
”The Synbiotics are considered excellent replacement substitutes for antibiotics or antimicrobial agents in animal health and production. However, Saccharomyces cerevisiae (S. cerevisiae) yeast contains a variety of nutrients, including proteins, polysaccharides, short peptides, amino acids, vitamins, trace minerals, nucleotides, and unidentified growth factors, it is frequently utilized as a synbiotic supplement in animal production . Therefore, it has been reported to improve animal production performance, enhance immune function, regulate intestinal flora balance, promote intestinal development, and improve meat quality. Prebiotics are comprised of indigestible carbohydrates that can be offered to animals to alter the microbial population balance and activity in the gut. Mannan-oligosaccharide (MOS) and β-glucan are prebiotics extracted from the cell wall of the S. cerevisiae yeast. The MOS and β-glucans are the emerging feed additives that have the biological functions to encouraging feeding and growth performance, regulating intestinal flora, enhancing animal immunity, and improving gastrointestinal development in animals .Symbiotics can be defined as a combination of selected synbiotic and prebiotic. The principal purpose of that type of combination is to stimulate the proliferation of synbiotics by providing specific substrate for their fermentation in the gastrointestinal tract. They are beneficial to the host by increasing the survival and deposition of viable microbiological nutritional supplements in the gastrointestinal tract. Therefore, it’s crucial that a product created with a proper ratio of synbiotics and prebiotics has superior qualities to those obtained from either prebiotics or synbiotics alone. The experiment was conducted at a governmental station located in El-Serw, Agriculture Research Center, Ministry of Agriculture, Egypt, while, the chemical analyses were run at the laboratory of the Animal Production Department, Faculty of Agriculture, Mansoura University.
Synbiotics are considered excellent replacement substitutes for antibiotics or antimicrobial agents in animal health and production. However, Saccharomyces cerevisiae (S. cerevisiae) among all the yeast species has been widely used as synbiotic supplementation in animal production, since it is rich in proteins, polysaccharides, small peptides, amino acids, vitamins, trace elements, nucleotides, and some unknown growth factors.Therefore, it has been reported to improve animal production performance, enhance immune function, regulate intestinal flora balance, promote intestinal development, and improve meat quality.Forty-five New Zealand White male rabbits (aged seven weeks, weighing 1075 ± 9.78 g) were used in the experiment and randomly allotted to five similar groups (9 rabbits / group).Five pelleted experimental diets were contained to levels of (0.0, 0.05, 0.1, 0.15 and 0.2 % Synbiotic).The obtained results could be summarized as follows:Growth performance:The effect of feeding diets at level 0.5 g synbiotic / kg diet was significantly higher in LBW of rabbits at 8 week up to 13 week the control diet or other feed additives. The feed additives showed significant effect on live body weight of growing rabbits throughout the whole experimental period from 7 to 13 weeks of age with diets without feed additives or with synbiotic levels (0.0, 0.5, 1.0, 1.5 and 2.0 g / kg diet) (2203, 2323, 2197, 2153 and 2050 g, respectively) .
The effect of feeding diets at level 0.5 g synbiotic / kg diet was significantly (p< 0.05) higher in ADG of rabbits at 8 week up to 13 week the control diet or other feed additives.The feed additives showed significant effect on the average daily gain of growing rabbits throughout the period from 7 to 10 weeks as shown in or throughout the period from 10 to 13 weeks and the whole experimental period from 7 to 13 weeks of age with diets without feed additives or with synbiotic levels (0.0, 0.5, 1.0, 1.5 and 2.0 g / kg diet) (26.9, 29.7, 26.7, 25.6 and 23.3 g, respectively).There was a significant effect (p< 0.05) on DMI with feeding on the diet with feed additives at 7 up to 9 weeks than feeding the control diet. The average DMI of the whole period from 7 to 10 wks ware significantly higher in diets with feed additive than the control diet, the DMI was significantly higher when feeding on the diet with adding 2.0 g synbiotic / kg diet than the other experimental diets. The whole experimental period from 7 to 13 weeks of age with diets without feed additives or with synbiotic levels (0.0, 0.5, 1.0, 1.5 and 2.0 g / kg diet) (76.9, 77.8, 78.0, 78.2 and 78.7 g, respectively).The feed conversion ratio from 7 to 13 weeks of age was higher (p < 0.05) with feeding the diet with added synbiotic at 2.0 g / kg diet than the other experimental diets, while the FCR was decreased (p < 0.05) with adding 0.5 g / kg diet than the basal diet or added 1.0 or 1.5 g synbiotic / kg diet. The same trend was observed of the period from 7 to 10 weeks or from 10 to 13 weeks. The average of the feed conversion (FCR) of whole period from 7 to 13 wks , when feeding the basal diet without or with different levels of synbiotic (0.0, 0.5, 1.0, 1.5 and 2.0 g / kg diet ) (2.89, 2.67, 2.89, 3.02 and 3.29, respectively).The live body weight, hot slaughter weight, viscera weight, and hot carcass were higher (p < 0.05) with added 0.5 g synbiotic / kg diet than the other diets and there was significant effect on dressing % (60 %). There were no significant effects on head, liver, leg, fur, kidney and heart weights among the experimental diets.
Digestion coefficients and feeding values:The digestibility of dry matter and organic matter were linearly increased (p < 0.05) in response to the increasing level of synbiotic in the diet. The rabbits’ digestibility of ether extract, and nitrogen-free extract increased (p < 0.05) to the increasing of synbiotic level.Regarding the feeding values, the increasing of synbiotic level in the diet. However, the lowest synbiotic supplementation (0.5 g/kg diet) showed the highest (p < 0.05) nutrient digestibility coefficient and feeding values compared to other groups. The synbiotic supply of 0.5 g/kg diet improved (p < 0.05) the digestibility of organic matter (67.52 %) in comparison with the control group (64.5 %). No differences were detected for the crude protein and crude fiber among the 0. 5, 1.0, 1.5 and 2.0 g/kg diet of synbiotic supplementation groups, and compared to those in the control group.The digested ether extract (DEE %) and digested nitrogen free extract (DNFE %) were higher (p < 0.05) with synbiotic supplementation at 0.05 % of the diet than the other diets. Digested energy (kcal/kg) was higher (p < 0.05) with 0.05 % synbiotic (2417.1 kcal/kg) than the other diets, while the DEI/DCPI values were higher (p < 0.05) with feeding on the control diet or supplemented with 0.05 % synbiotic (21.26 and 21.97, respectively) than the other diets.The blood biochemical and hematological parameters:The serum biochemical variables of growing rabbits were affected (p < 0.05) by synbiotic supplementation in the diet, except for globulin, alanine aminotransferase, and creatinine. The serum concentrations of total protein, albumin, alanine aminotransferase, urea, triglycerides, HDL, LDL, and glucose quadratic ally responded (p < 0.05) to the increasing level of synbiotic in the diet. The aspartate aminotransferase concentration linearly decreased (p < 0.05) by increasing the symbiotic level in the diet. With quadratic responses (p < 0.05) to the synbiotic level in the diet, the lipase and amylase concentrations were linearly increased (p < 0.05) and cortisol decreased (p < 0.05). The synbiotic level of 0.5 g/kg diet showed the most effective biochemical variables response (p<0.001) compared with control group, followed by level of 1.0 g/kg diet group. No differences were observed between the higher doses of supplementation (1.5 and 2.0 g/kg diet) but both groups obtained lower (p < 0.05) concentrations of aspartate aminotransferase and cortisol, and higher (p < 0.05) amylase and lipase values compared with control group. Growing rabbits were affected (p < 0.05) by synbiotic supplementation in the diet, except for platelet count, MCV, MCH, lymphocytes and neutrophils. The concentrations of IgG, IgM, red blood cells, hemoglobin, hematocrit and platelet count were increased (p < 0.05) while the white blood cells decreased (p < 0.05) by increasing the synbiotic level in the diet. However, the synbiotic supplementation level of 0.5 g/kg diet showed no differences for all studied hematological parameters compared with control group. The 1.0 g/kg diet of synbiotic supplement tended to do so as well but showed (p < 0.05) higher IgG and lower white blood cells in comparison to control group. The highest synbiotic supplementary dose (2.0 g/kg diet) observed the best values of IgG, IgM, and hematological parameters without differences with the 1.5 g/kg diet group.4- Intestinal Histomorphology: The results of representative photomicrograph of intestine from different treatment groups are showed that the villus height was higher (p < 0.05) with feeding R1or R2 or R3 than feeding R4 or R5. The villus width was higher (p < 0.05) with feeding on R1 than feeding on R2 or R3 or R4 or R5 diets. The sub mucosa thickness was higher (p < 0.05) with feeding on R5 than the other diets, while the muscular thickness was decreased (p < 0.05) with feeding on R2 or R3 or R4 than feeding on R1 or R5 diets.In summary a conclusion
Supplementing fattening rabbit diets with synbiotic enhanced growth performance by improving the feed utilization, immune response, serum lipid profile, and intestinal morphology. The presented results for DEI/DCP ratio and the growth performance of growing rabbits, were increased with feeding on R1 or R2 or R3 than feeding on R4 and R5.Based on the current study findings, it would be appropriate to add 0.5 g/kg diet of the experiment synbiotic combination of S. cerevisiae as probiotic and prebiotics of β-glucan and MOS during the fattening period as well as ameliorate the carcass traits. Current synbiotic showed synergistic effects that could pave the way for more sustainable rabbit production and could be a promising approach to minimize the use of antibiotics and therefore recommended for use in rabbits’ husbandry under commercial production conditions. However, the understanding of the regulatory role of current synbiotic on the intestinal health and the mechanism of action warrants further study. ”