الفهرس 
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Abstract
This experiment was carried out at the Advanced Laboratory of Animal Nutrition, Animal and Fish Production Department, Faculty of Agriculture, Alexandria University, Egypt. The aims of this experiment were to asses the effects of inclusion various levels of HA, FA and their mix HFmix on gas and CH4 production, rumen degradability and fermentation characteristics in vitro.Rumen contents were collected freshly from adult slaughtered of three Egyptian buffalo steers at the slaughter-house of the Faculty of Agriculture, Alexandria University. Basal substrate (50:50) was incubated without additives (control) and with different levels of HA (2, 4 and 6 g/ kg DM), FA (1, 2 and 3 g/kg DM) and HFmix (2+1), (4+2), (6+3) g humic: fulvic /kg DM for the in vitro assay using semi-automatic system of GP for 24 h. The obtained results were as follow:
❖ Humic acid (HA) supplementation: The net GP (ml/g DM), CH4 (ml/g DM) and net CH4 (ml/g TDOM) were decreased linearly (P <0.001) with the various levels of HA supplementation groups. The different levels of HA supplementation deactivate the TDOM, TDDM, net GP (ml/g TDOM) and PF compared to the control. The NH3-N concentrations were decreased (P = 0.046) quadratically (P = 0.021) with the supplementation of different levels of HA compared to the control group. Similarly, both total and individual VFA quadratically decreased with the HA treatment levels. The different levels of HA had no effects on rumen pH, acetate to propionate ratio (C2:C3) and protozoa count (105cell/ml) compared with the control.
❖ Fulvic acid (FA) supplementation: The net GP (ml/ g DM), CH4 (ml/ g DM), net GP (ml/ g TDOM) and net CH4 (ml/ g TDDM) were decreased (P < 0.05) compared with control and this decrease had quadratic (P < 0.05). No affects were observed with the different levels of FA supplementation to the diet on TDOM, TDDM and PF compared to the control. The NH3-N was decreased (P > 0.05) with the supplementation of different doses of FA to the diet compared with the control and this decrease was linear (P = 0.015) and quadratic (P = 0.008). in contrast the FA treatment levels had not affected both total and individual SCFA, except the C2:C3 ratio that quadratically decreased (P = 0.006).