Rumen fermentation kinetics and nitrogen degradability of commonly used ruminant feedstuffs In vitro

The study was conducted to evaluate tropical feedstuffs used in feeding ruminants for rumen fermentation kinetics and N fractions. The feed samples selected for the study included 8 protein sources, 9 energy sources, 8 unconventional byproducts, 5 roughages and 6 complete diets. The D (potential gas production, ml/g DM), and k (h⁻¹) (rate of gas production) for protein sources varied from 141.0 to 296.5 and 0.0858 to 0.1562, for energy sources from 327.0 to 476.5 and 0.0544 to 0.1078, for unconventional byproducts from 46.3 to 495.9 and 0.0233 to 0.1117, for roughages from 245.9 to 303.8 and 0.0219 to 0.1092 and for the six diets it varied from 218.4 to 301.8 and 0.0553 to 0.0640. Total N content (g/kg DM, Mean±SD) for protein sources, energy sources, unconventional byproducts, roughages and complete diets was 54.4±14.6, 15.8±7.2, 11.1±6.7, 16.7±9.6 and 20.2±0.13, respectively. Potentially digestible N was more than 90 per cent for most of the feedstuffs with the exception of tapioca peel (82.3%), tapioca meal (76.4%), coarse wheat bran (83.9%), Bengal gram husk (82.9%), chicory bran powder (83.3%), poha bran (75.0%), ragi husk (78.1%), finger millet straw (71.1%), hybrid napier (76.1%) and rice straw (85.8%). However, among the protein sources, the N rapidly degraded in the rumen was maximum in ground nut meal (59.7%), followed by rapeseed meal (35.5%), gingelley cake (32.9%), ambadi cake (31.5%), cotton seed meal (24.4%), coconut meal (20.1%), soybean meal (17.2%) and sunflower meal (6.5%). The N solubility in buffer and detergent solutions and fermentation kinetics within one class of feedstuffs may be an indicator of variability in the degradation of protein and energy, respectively in rumen.