Comparison of ruminal digestibility of Origanum onites L. leaves in dairy buffalo and cows

This experiment evaluated the ruminal digestibility of Turkish oregano leaves in dairy buffalo and cows. Ruminally cannulated, multiparous Brown Swiss cows ( n = 3) and water buffalo ( Bubalus bubalis ; n = 3) were used in the experiment. The ad libitum basal diet was balanced to NRC requirements for a dry, nonpregnant multiparous dairy cow (680 kg) and consuming 12.8 kg of DM/day. Air-dried, ground, weighed oregano leaves were inserted in the rumen of all animals before the morning feeding within heat-sealed nylon bags (4 replicates per treatment and time point). After incubation (4, 8, 24, 48, and 72 h), dry matter (DM), crude protein (CP), aNDFom, and ADFom concentrations were determined and compared to initial leaf chemical composition. The means for in situ disappearance (ISD, %) of DM, aNDFom, and ADFom did not differ between the species, but ISD of CP was greater in buffalo than the cows ( P = 0.05) after 72 h incubation. The lag time of kinetic degradation curves, the potentially degradable fraction ( b ), hourly degradation rate ( c ), and undegradable fraction were similar between species. The immediately degraded fraction ( a ) and effective digestibility (ED) of CP were greater in buffalo than the cows ( P = 0.04), but the a fraction and ED of other nutrients showed no differences between the species. In conclusion, CP of oregano leaves are degraded more rapidly in the rumen of dairy buffalo than cows, primarily due to a large difference in the rapidly soluble CP fraction in the buffalo.