标题：Evaluation of dietary supplementation of B vitamins and HMBi on fermentation kinetics, ruminal or post-ruminal diet digestibility using modified in vitro techniques
摘要：The effects of dietary supplementation of HMBi, alone or in combination with B
vitamins were investigated on fermentation characteristics and in vitro ruminal and
post-ruminal digestion using three modified techniques. A total-mixed ration was
formulated using the assumptive animal information by CPM-Dairy software and
used as a substrate. Eight dietary treatments arranged in a 2×2×2 factorial design
with factors of HMBi (0 and 0.13% DM), folic acid (0 and 0.012% DM), and
vitamin B12 (0 and 0.0021% DM). In the first experiment, fermentation
characteristics and parameters were evaluated for dietary supplements’ effects using
in vitro gas measuring technique. In the second experiment, an in vitro modified
batch culture technique was performed to study on in vitro digestion and
fermentation end products. Finally, ruminal and post-ruminal digestibility of crude
protein was investigated by a modified three-step technique. In comparison with
control, supplementation of HMBi declined cumulative gas production (P < 0.001)
and fermentation parameters (P < 0.01) all over the incubation times. Interaction
effects between B9 and B12 were identified (P ≤ 0.01) that were associated with the
decreased cumulative gas production (P ≤ 0.01), A fraction (P = 0.01) and C fraction
(P = 0.02). Digestion of CP declined at first incubation time by alone
supplementation of HMBi, folic acid and B12 but it was improved after that.
Supplementation of folic acid alone or in combination with HMBi increased
(P≤0.05) NDF digestion for 4 and 24 h of incubation. Ammonia-N was decreased
significantly with supplementation compared to intact diet. Total VFA was also
enhanced (13 to 46%) by dietary supplementation of B12 compared to
unsupplemented diet. Highest VFA was associated with HMBi from 24 h and
thereafter. Addition of HMBi individually or with B9 and B12 increased post-ruminal
CP while B vitamins had not the same effect of supplementing individually. Results
suggest that supplementation of diet with HMBi and B vitamins, modify rumen
fermentation by decreasing gas production, enhancing production of VFA and
increasing utilization of ammonia-N in the rumen.
关键词：folic acid; vitamin B12; HMBi; post;ruminal digestion; in vitro
