The Impact of Humic Substances as Feed Additive on Ruminal Fermentation

Abstract

The rumen is settled with a complex microbial ecosystem where feeds consumed by animals are digested with the help of rumen microorganisms, which play an important role in contributing nutrients to the host animal. This study focused on investigating the effect of humic substances (HS) dietary inclusion on the protozoal community in the rumen and qualitative parameters of the ruminal fluid. In the presented research, three cannulated beef cows were housed in individual pens and were fed with the basal diet enriched with the organic feed additive Humac®Natur AFM (comprise: 65 % humic and 5 % fulvic acids, Ca 42.28, Mg 5.11, Fe 19.05 g/kg, Cu 15, Zn 37, Mn 142, Co 1.24, Se 1.67, Mo 2.7 mg/kg of DM) in 3 different concentrations: 60 g/day (4,8 g/kg of DM) and 110 g/day (8,9 g/kg of DM) and 200 g/day (16,1 g/kg of DM). The rumen liquor of each animal was collected two times per week via a rumen cannula with a probe connected to a vacuum pump for further laboratory analyses. Test of rumen fluid included: measurement of pH, physical characteristics, the concentration of nitrogenic compounds and ammonia, determination of rumen protozoa activity, and counting of the total number of protozoal ciliates; the motility of ruminal ciliates was also observed. The rumen pH level was affected by the sampling period, but diet treatment had no significant impact on rumen pH. The pH values in rumen fluid samples were within the normal range, the same as physical characteristics (color, odor, consistency, and sedimentation time). In conclusion, dietary HS supplementation significantly reduced protozoal activity in the rumen in all tested concentrations, which was also in correlation with lower protozoal motility and ammonia concentrations.