The effect of licorice extract on growth performance of fattening lambs, fermentation parameters and rumen protozoan population

In order to investigate the effect of licorice extract (LE) on growth performance, fermentation parameters, and rumen protozoan population in fattening lambs, 28 male lambs weighing 36.45 ± 1.75 kg in a completely randomized design with four treatments and seven replicates were used. Experimental treatmeشnts included: control, basic diet without licorice extract, and treatments one to three included basic diet plus five, 10 and 25 mg of LE per kilogram of DM. The ratio of forage to concentrate was 30:70, which was given to the animals as per their appetite. Adding 25 mg of the extract to the diet increased the daily gain and improved the feed conversion ratio (P<0.05). The pH of rumen fluid and gas production increased at the level of 25 mg of extract (P<0.05). Methane production was not affected by adding LE to the diet. The changes in metabolizable energy, degraded organic matter and concentration of volatile fatty acids in diets containing 5 and 25 mg of LE were more than other groups (P<0.05). The total population of protozoa as well as the number of Entodinia decreased by feeding diets containing LE (P<0.05) but the number of Isotrichida increased, significantly. Based on the results of this research, adding 25 mg/kg of licorice extract to the diet improves the rumen metabolism and the performance of fattening lambs, but it had no effect on the amount of energy loss in the form of methane.