الفهرس 
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Abstract
The present work was designed to study the potential effects of the probioticSaccharomyces cerevisiae [either live yeast cells (levucell SC 20)® or yeast Culture (Diamond V XP™)®] supplementation to lambs on rumen ecology, immunity parameters, blood serum biochemical parameters, bodyweight and bodyweight gain in a try to gauge their use efficacy in fattening lambs under Egyptian environment.
Fifteen native growing male lambs (the mean (±SD) of initial age and body weight of 4.88±0.91months and 23.21±2.75 kg respectively) were randomly divided to one of three dietary treatments in a three months completely randomized design experiment as:
1. The basal formulated ration without any supplementation and represented the control group (group C).
2. The basal formulated ration and each lamb was orally supplemented with 0.5 g of live yeast (levucell SC 20)® daily till the end of the experiment (group Y)
3. The basal formulated ration and each lamb was orally supplemented with 7 g of yeast culture (Diamond V XP™)® daily till the end of the experiment (group YC).
Rumen liquor and blood samples were collected at zero day (before administration of probiotics), and at 15th day, then every 15 days until the 90th day post supplementation.
The results could be summarized as follows:
(A)Clinical examination of the animals:
•The clinical examination of different body systems revealed no apparent clinical abnormalities throughout the experimental period.
(B) Rumen ecosystem:
• The values of rumen pH in probiotic-treated groups (Y and YC) were significantly decreased (P ≤ 0.05) comparing with that in control group in the time extended from 60th day till the end of the experiment.
• Ammonia nitrogen concentrations showed significant decrease (P ≤ 0.05) in both supplemented groups(Y and YC)at the 30th and 90th days of the experiment comparing with non-supplemented lambs in group (C).
• Protozoal counts significantly (P ≤ 0.05) increased in both treated groups comparing with non-supplemented lambs at 15th, 75th and 90th days of the experiment.
• Concentrations of rumen total volatile fatty acids were significantly higher (P ≤ 0.05) in the yeast and yeast culture supplied lambs (groups Y and YC) than that found in lambs of group (c) over the time, except at the 15th day, the variation was insignificant (P ≤ 0.05).
(C) Leukogram:
• Total leucocytic counts and neutrophils percentages showed no significant variations (P ≤ 0.05) among the animal groups throughout the experiment.
• The lymphocytes percentages of the lambs supplemented with probiotics (groups Y and YC) were insignificantly higher (P ≤ 0.05) than that of the lambs in the control group over the experimental period
• Percentages of monocytes and eosinophils showed no significant differences among the lambs of the three groups during the experimental period.
(C) Blood serum biochemistry:
• The serum activities of AST of the probiotic-treated lambs (groups Y and YC) were insignificantly slightly higher (P≤0.05) than that of control lambs, over the period of the experiment.
• The serum ALT activities of the probiotic-treated lambs were insignificantly (P≤0.05) lower than that of control lambs.
• Serum ALP activities of group (Y) and group (YC) were insignificantly (P≤0.05) slightly higher than that of control group. At 30th and 60th days of the experiment, there were significant (P≤0.05) increases in ALP activity in (YC) group comparing with that in control lambs.
•LDH activities fluctuated insignificantly between the three groups of lambs.
• GGT activities were decreased in both (Y) and (YC) groups with significant reduction (P<0.05) recorded in both (Y) and (YC) groups at the 15th and 90th days of the experiment.
• CK activities tend to be lower in both yeast supplemented groups (Y and YC) when compared with the control one.
•Total protein and globulins showed no significant differences (P≤0.05) among the groups during the experiment.
• The levels of serum albumin and A/G ratio have increased gradually in each group throughout the experimental period until they reach the peak at the 45th day of the study, then begin to decline.
•The serum concentrations of IgA, IgG and IgM in lambs provided with probiotics (groups Y and YC) had insignificant increases (P≤0.05) comparing with those that did not take probiotics (group C) during the period after the 45th day of the experiment.
• Glucose levels were increased in both supplemented groups (Y and YC) comparing with the control group throughout the experimental period.
• The levels of serum triglycerides showed that, the lambs in both supplemented groups (Y and YC) had lower levels of triglycerides than that in group (C) over the time of the experiment.
• Cholesterol, HDL and LDL concentrations in yeast and yeast culture-treated lambs tended to be insignificantly lower(P≤0.05)than that in control lambs throughout the period of the experiment.
• Blood serum urea and creatinine values tended to be lower in probiotic-treated lambs (Y and YC groups) comparing with those in control group (C), almost over the time of the experiment.
• Serum calcium and phosphorus levels tended to be insignificantly fluctuated (P≤0.05) among the groups of lambs throughout the period of the study.
(D) Bodyweight and bodyweight gain:
• Bodyweights and bodyweight gains were insignificantly increased in treated lambs throughout the study period, except in the late period of the study (at 75th and 90th days), significant increases (P≤0.05) were observed in treated groups.
Conclusions
Probiotics including yeast and yeast culture products appear as promising feed additives, they are of natural origin and generally regarded as safe for animals. Moreover, they may have the potential to improve production performance and health status of small ruminants.
This study has highlighted the possibility of using the yeast or yeast culture probiotics as a safe growth promoter in lambs during the fattening period, as both yeast and yeast culture administrations had some positive effects on lambs including:
• Stimulating the energy metabolism.
• Protecting the renal functions.
• Increasing the levels of immunoglobulins (IgA, IgG and IgM), which may increase the resistance of the animals to the diseases.
• Stabilizing the rumen ecosystem.
• Increasing the rumen protozoal counts that will enhance the feed digestibility and increase the rumen total volatile fatty acids.
• Enhancing the bodyweights and bodyweight gains without any adverse effect on health status, as well asno residual effect on animalnproducts.