Feeding Damascus goats humic or fulvic acid alone or in combination: in vitro and in vivo investigations on impacts on feed intake, ruminal fermentation parameters, and apparent nutrients digestibility

In vitro and in vivo experiments were carried out to investigate the effects of the supplementation of different levels of humic and fulvic acids alone or their combination (2:1 ratio) on ruminal fermentation constituents, and nutrients digestibility in goats. The treatments in Exp. 1 were the following: (1) basal substrate (50% concentrate: 50% forage) was incubated humic at 0, 2, 4, and 6 g/kg DM; (2) fulvic at 0, 1, 2, and 3 g/kg DM; and (3) a combination of humic and fulvic (in a 2:1 ratio) at 0, 3, 6, and 9 g/kg DM" of treatments. The results of Exp. 1 revealed that methane (CH 4 ) production was linearly decreased ( P < 0.001) upon increasing humic doses. Whereas, the combination of fulvic acid with humic acid resulted in a quadratic decrease ( P < 0.001) in net CH 4 production. Supplementing humic and fulvic acids, either separately or in combination, resulted in reduced ( P < 0.05) ammonia nitrogen (NH 3 -N) and total volatile fatty acid (VFA) concentrations. In Exp. 2 to further examine the findings obtained in Exp. 1, forty Damascus non-lactating goats (2–3 years of age and body weight 29 ± 1.5 kg) were fed the same basal diet as in Exp. 1, plus one of four treatments. Treatments were the following: (1) control (no supplement); (2) basal diet plus 5 g humic alone; (3) basal diet plus 2.5 g fulvic alone, and (4) basal diet plus 7.5 g their combination. Goats fed diets supplemented with humic acid, fulvic acid, either alone or in combination, increased concentrations of butyrate ( P = 0.003), total VFA ( P < 0.001), and improved ( P < 0.001) digestibility of nutrients, but reduced ( P < 0.001) ruminal NH 3 -N concentrations. In conclusion, applying humic and fulvic acids alone or in combination attenuated in vitro CH 4 production, while improved intake and diet digestibility without adverse effect on rumen fermentation profiles in Damascus goats.