Effects of Supplementing Aqueous Direct-Fed Microbials on In Vitro Fermentation and Fibrolytic Enzyme Activity in the Ruminant Nutrition

반추가축영양에 있어서 액상미생물제제의 첨가가 In Vitro 발효성상과 섬유소분해효소활성에 미치는 영향

This study was conducted to determine effects of supplementation levels of aqueous direct-fed microbials (DFM; Bacillus spp.) to TMR(exp. 1.) and aqueous DFM addition under the various ratios of starch and cellulose(exp. 2.) on ruminal fermentation and fibrolytic enzyme activity. In experiment 1, ruminal fluids taken from rumen-cannulated Holstein cows were incubated during 24 hr by using TMR as substrates. Aqueous DFM was applied at a rate of 0, 0.025 and 0.05%, respectively. The pH of 0.025% treatment was not significantly different from that of control at 6 and 9 hr, but it was significantly lower (P<0.05) than 0.05% treatment. Concentrations of ammonia-N and VFAs were not affected by supplementing aqueous DFM. The A:P ratio of 0.05% treatment was significantly increased(P<0.05) by supplementation of aqueous DFM as compared with that of control at 24 hr. Although overall fibrolytic enzyme activities were not significantly affected by supplementing aqueous DFM, CMCase(carboxymethylcellulase) activity showed significant increase(P<0.05) compared to control at 6hr. However, the xylanase activity of 0.05% treatment significantly decreased(P<0.05) at 12 hr due to the application of aqueous DFM. There was no significant difference for in vitro dry matter disappearance among treatments. In experiment 2, ruminal fluids were incubated under the condition of various ratios of starch to cellulose(90:10, 70:30, 50:50, 30:70 and 10:90) with or without aqueous DFM(0.025%). Ruminal pH was unaffected by the addition of aqueous DFM, however, as increased level of starch, ruminal pH partially showed significant decrease(P<0.05). Ammonia-N concentration was not affected by aqueous DFM and ratio of starch and cellulose. On 9 hr incubation, DFM addition at a ratio of 70:30 showed significantly (P<0.05) lower value of ammonia-N(35.65 mg/dL) than that(65.05 mg/dL) of control. Concentrations of VFAs were significantly increased(P<0.05) by aqueous DFM addition compared with control at the same ratio on 6 hr incubation. The overall CMCase activity was not affected by aqueous DFM addition. However, the xylanase activity by aqueous DFM partially showed significant differences at the ratios of 90:10, 30:70 and 10:90. Our results indicated that supplementation of aqueous DFM did not significantly improve in vitro fermentation and fibrolytic enzyme activity. In addition, the DFM utilized in this study did not show consistent results by having various effects on ruminal fermentation under different feeding regimens.

본 연구는 액상 DFM(Bacillus spp.)을 완전혼합사료(실험 1) 및 다양한 비율의 starch와 cellulose에 적용(실험 2) 하였을 때, 반추위내 발효와 섬유소분해효소활성에 미치는 영향을 평가하기 위해 in vitro 배양을 24시간동안 실시하였다. 실험 1의 처리구는 완전혼합사료에 액상 DFM 0%(대조구), 0.025%, 0.05%로 각각 첨가하였다. 실험 1에서, 0.025%구는 배양 6, 9시간에서 대조구와는 유의한 차이가 없었으나, 0.05%구보다는 유의하게 낮은 결과를 보였다(P<0.05). 암모니아질소농도와 휘발성지방산농도는 액상 DFM에 의하여 영향을 받지 않았다. 하지만, A:P비율은 DFM의 적용으로 배양 24시간에 대조구에 비하여 0.05%구에서 유의한 증가를 나타내었다(P<0.05). 액상 DFM적용에 의한 섬유소분해효소활력은 전반적으로 유의한 효과가 나타나지 않았지만, CMCase는 배양 6시간에 대조구에 비하여 유의한 증가를 나타내었다(P<0.05). 하지만, xylanase는 배양 12시간의 0.05%구에서 오히려 액상 DFM의 적용으로 유의하게 감소하였다(P<0.05). 반추위내 건물소실율은 액상 DFM의 첨가수준에 의해 유의한 차이가 나타나지 않았다. 실험 2는 다양한 비율(90:10, 70:30, 50:50, 30:70, 10:90)의 starch와 cellulose에 액상 DFM을 각 비율에 대하여 대조구(0%)와 첨가구(0.025%)로 나누어 반추위액을 이용하여 배양하였다. 반추위내 pH는 액상 DFM의 첨가로 유의한 영향을 받지 않았고, starch의 비율이 증가함에 따라 부분적으로 유의하게 감소하였다(P<0.05). 암모니아질소농도는 액상 DFM의 첨가와 starch 및 cellulose의 비율에 의하여 유의한 영향을 받지 않았다. 하지만, 배양 9시간의 70:30비율에서 액상 DFM첨가구가 35.65mg/dL의 암모니아질소농도를 나타내어 대조구의 65.05mg/dL에 비하여 유의하게 감소하였다(P<0.05). 휘발성지방산농도는 70:30비율의 6시간 배양에서 액상 DFM구가 대조구에 비하여 유의한 증가를 나타내었다(P<0.05). 액상 DFM의 첨가는 CMCase에는 전반적으로 유의한 영향을 미치지 않았다. 그러나 xylanase에는 90:10, 30:70 및 10:90구에서 부분적인 유의성이 인정되었다. 본 연구결과로부터, 액상 DFM의 적용은 in vitro 발효성상과 섬유소분해효소활성을 유의적으로 향상시키지 않았고, 사료의 조성에 따라 그 효과는 다양하게 나타나 일관성이 없는 것으로 평가되었다.