This study was aimed to evaluate correlation between in vitro gas production and in situ nylon bag technique for various sources of Dried Citrus Pulp (DCP). In vivo experiments to determine organic matter degradability (OMD) values of forages are expensive and laborious, impair animal welfare and are not suited for routine analysis. Therefore alternative in vitro techniques to predict OMD were developed in the past 40 years, such as the in vitro gas production technique. The method of sample preparation to measure DM degradability with the in situ nylon bag method was used as described by Dulphy et al. (1999). Samples were incubated in the rumen of 3 fistulated steers. The bags were removed following 0, 2, 4, 8, 12, 24, 36, 48, 72 and 96 h after incubation. In vitro gas production for the same components, with rumen liquor of same animals at same times, was measure. Regression model was made among the data of in situ and in vitro measurements for DM with the best r2 calculated by SAS 9.1 program. Correlations for DM degradability measured by two methods were 0.94, 0.94, 0.92, 0.88, 0.95, 0.94, 0.96, 0.94, 0.96 and 0.91 for C. Sinensis cul. Tamson, C. Sinensis cul.siahvaras, C. Sinensis cul. Brohen, Citrus unchiu, C.reticulata cul. Page, C.reticulata cul. Celemantin, C.reticulata cul.younesi, Citrus aurantifolia, Citrus aurantium and Citrus paradisi respectively. R2 between gas production and in situ DM degradability are high and indicated that both techniques can apply for determination of fermentation potential in the rumen. Observed DM values of degradability quite agree with gas production data during different time of incubation. According to the regression models, in vitro gas production for the DM contents of various sources of DCP could be used instead of the in situ technique at lower cost in shorter time.

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