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Abstract Two experimental feeding trials were conducted to visualize the response of cross - breeds buffalo calves to dietary supplementation of two levels (0.5 or 1 g/h/d) of Saccharomyces cerevisiae (commercially available SC product) with two different (F: C) forage to concentrate ratio diets. A total of sixty (60) apparent healthy intact male buffalo calves of 13 to 14 months age , of an average weight of (246.8±7.1 kg) were randomly divided and allocated into two major experimental groups (A, and B). group (A) were used in the 1st trial received diet contains (30:70) forage to concentrate ratio on DM basis, while group (B) were used in the 2nd trial and received diet contain 50:50 of (F:C) on DM basis. Animals of both groups (A, B) were sub- divided, and assigned into three experimental groups (10 calves/ group). In both trials the first (G1) was fed on basal total mixed ration (TMR without any supplementation and served as control group, the second (G2) was fed on the same ration of (G1) supplemented with 0.5 g/h/d SC product; meanwhile the third (G3) was fed on the same ration of (G1) supplemented with 1 g/h/d SC product in their ration. Calves in all the six groups were fed ad libitum and both feeding trails lasted for 180 days in addition to 14 days as acclimatization period.in the 1st experimental groups (A) the dietary supplementation of S. cerevisiae at both levels of supplementation (G2,G3) resulted in significant (p<0.05) increase in average daily gain compared to the control. DMI, total weight gain, and final body weight of (G3) were significantly (p<0.05) higher compared to both (G2) and the control groups. FCR of (G3) surpassed all groups in terms of FCR. Rumen juice pH, total N protein content and total ruminal ifusoria count and activities were significantly (p<0.05) higher in both supplemented groups compared by control whereas their lactate concentrations was significantly (p<0.05) lower. (G3) showed a significant (p< 0.05) increase in total volatile fatty acids(TVFs), acetate, propionate, and butyrate concentrations with (p< 0.05) decrease in ruminal NH3-N compared to the control. The response of the calves to supplemented dose regarding its effects on rumen parameters was different. Higher level of supplementation (G3) showed significant increase (p<0.05) of total N protein, total ruminal ifusoria count and activities, (TVFAs) and acetate level. In addition to significant (p<0.05) decrease of lactate concentration compared by the lower level (G2); a situation that indicated better impact of the higher level of supplementation. Serum glucose were significantly (p<0.05) higher in (S.C) supplemented groups, whereas, serum AST, ALT, and creatinine were not affected. Blood urea nitrogen was significantly (p<0.05) lower (G3) compared to the control. Quantitative and qualitative characteristics of the carcasses were similar in all groups. The cost of feed per /kg gain was lower in both treated groups. The higher dose was more cost effective and time saver than the lower dose level of supplementation. In the 2nd experimental groups (B) both levels of S. cerevisiae supplementation resulted in significant (p<0.05) increase in total weight gain, average daily gain, and DMI in comparison to control group. FCR of (G2) surpassed all groups in terms of FCR. Rumen juice total ifusoria count and activities were significantly (p<0.05) higher in both levels of (S.C) supplementation compared by the control. The low level (G2) showed significant (p< 0.05) increase in propionate, decrease (p<0.05), acetate to propionate ratio (A: P) compared to the control (G1). Meanwhile a higher level of (S.C) supplementation (G3) resulted in significant (p< 0.05) increase in total volatile fatty acids (TVFA), (A: P) compared to the control. The response of the calves to supplemented dose regarding its effects on VFA profile was different. Lower level (G2) showed significant increase of propionate and decrease in acetate levels in comparison to the higher level (G3) a situation that indicates better impact of lower level of supplementation. Serum glucose, and total serum protein were significantly (p<0.05) higher in (S.C) supplemented groups, whereas, serum AST, ALT, urea and creatinine were not affected. Quantitative and qualitative characteristics of the carcasses were similar in all groups. The cost of feed per /kg gain was lower in both supplemented groups. The lower dose of SC supplementation was more cost effective than the higher dose of supplementation. It could be concluded that dietary supplementation with (S.C) to beef buffalo calves fed on TMR with different level of (F:C) ratio resulted in positive impacts not only on growth performances, rumen ecology, selected serum parameters but also it was proved to be cost effective and economically feasible. |