Effect of Concentrate: Roughage Ratio and the Addition of Kefir on the Production Characteristics of Ruminant in vitro

The stability of the gut ecosystem, especially the rumen, is an important area of research that has an impact on the use of feed additives and is associated with a number of diseases. The current study aimed to survey the effect of concentrate: roughage (C: R) ratio and the addition of kefir on the production characteristics of in vitro ruminant fermentation. In a 5x6 factorial order, six ratios of C: R (100:0, 80:20, 60:40, 40:60, 20:80 and 0:100) and five doses of kefir (0, 0.8, 1.6, 2.4, and 3.2 ml) were used, respectively. Gas production during incubation was estimated at 0- 96 h. During inoculation, the rumen fluid was obtained at 0, 4, 8, 12, and 24 h of incubation. Cumulative gas production, GPDM, GPOM, and GPNDF at 24 h was highest at the C: R ratio of 100:0 (67.82 mL, 75.92 mL/ 200 mg, 1979.15 mL/200 mg, and 11.11 mL/ 200 mg, respectively). The kefir addition improved the kinetics and gas production significantly. The highest in vitro dry matter and organic matter digestibility (IVDMD and IVOMD) were obtained at the C: R ratio of 100:0 (9.26% and 182.2% higher than those in C: R ratio of 0:100, respectively). The increase of concentrate diet ratio improved the overall volatile fatty acids (TVFA). No interaction effect on the gas production was detected between the C: R ratio and kefir. The microorganism populations were influenced neither by the level of concentrate nor by the level of kefir. Consequently, the high concentrate-to-roughage ratio and the addition of 1.6 mL kefir to the overall dietary substrate could promote rumen fermentation and feed digestibility without affecting microbe counts.