| Three simmental crossed steers (600±100kg body weight) fitted with permanent ruminal cannulas were used in two 3× 3 Latin square designs to study the effect of yeast culture on rumen fermentation and fiber digestibility. The basal diets of two designs consisted of corn, soybean meal and straw to formulate low, middle and high concentration diets with three forge I concentrate ratio of 30 ∶ 70,50 ∶ 50 and 70 ∶ 30 (air-dry basis) , and three diets were satisfied to 1.0, 1.5 and 2.0 times above maintenance level of intake respectively, which were pointed LC, MC and HC. Two designs is divided into control and treatment which supplemented the same yeast culture with equal dose. In order to decrease the unfavorable effect for diets' change, two designs were mixed three periods to implement. Each period was 28 days and was divided into two phages (control and treatment). The steers were fed the same diet in each period. Control (from 1st to 14th) and treatment (from 15th to 28th) were comprised by a 10-day adaptation and 4-day sample collection. The trial is aimed to study the effect of different concentration diets supplemented yeast culture on rumen pH, NH3-N, VFA (including acetate, propionate, butyrate, total VFA and the ratio of acetate/propionate), four main relative fibrolytic enzymes (xylanase, CMCase, salicinase and cellulase) and dynamic degradability and degraded parameters of DM, OM, NDF and ADF of straw. The results indicated that:1 On the values of pH in rumenThere were no significant effect on the values of pH in the same diet with different treatments (P>0.05). However, the mean pH values of steers fed low, middle and high concentration diets in treatments were increased 0.13, 0.07 and 0.04 respectively, compared with three diets in control. In different diets with the same treatment, there were significant effect between LC-YC and HC-YC (P<0.05). The values of pH decreased in control and treatment with the increased concentration of diets.2 On the concentrations of ammonia-N in rumenThere were no significant effect on the concentrations of ammonia-N in all trials(P>0.05). The concentration of MC-YC was lower than that of MC-CT, but LC-YC and HC-YC increased respectively, compared with LC-CT and HC-CT. The concentrations of ammonia-N reduced in treatments with the increased concentration of diets.3 On the concentrations of VFA in rumenThere were no significant effect on the concentrations of acetate, propionate and total VFA in all trials (P>0.05). However, the concentrations of acetate, propionate and total VFA in three diets in treatments were higher than those in control. In the same diet with different treatments, the concentration of butyrate in HC and the ratio of acetate/propionate in MC were significant effect between control and treatment (P<0.05). In different diets with the same treatment, the concentrations of butyrate between LC-CT and MC-CT, LC-CT and HC-CT, LC-YC and HC-YC, and MC-YC and HC-YC, and the ratio of acetate/propionate between LC-CT and HC-CT, MC-CT and HC-CT, LC-YC and MC-YC, and LC-YC and HC-YC were significant effect (P<0.05). With the increased concentration of diets, the acetate concentration and the ratio of acetate/propionate reduced in treatments, but the propionate and butyrate concentration increased in control.4 On the dynamic degraded parameters of DM, OM, NDF and ADF of straw in rumenThere was no significant effect on the dynamic degraded parameters a, b, c, EDPj and EDP2 of DM, OM and NDF in all trials(P>0.05). The "a" values of ADF in HC-YC were significant effect between control and treatment (PO.05), and the "a" value of HC-YC increased by 34.62% than that of HC-CT.5 On the activities of relative fibrolytic enzymes in rumenIn the same diet with different treatments, there were significant effect on xylanase activities between LC-CT and LC-YC and HC-CT and HC-YC, on CMCase activities between control and treatment in three diets, on salicinase activities between MC-CT and MC-YC and HC-CT and HC-YC, on cellulase activities be... |
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