Garlic: A potential alternative for monensin as a rumen modifier

The effects of supplementing a basal diet (CTR) with raw garlic (GAR) or garlic oil (GO) on rumen fermentation were evaluated. Monensin (MON, 33 mg/kg DM) was used as positive control. Four ruminally fistulated sheep were used in three experiments arranged as 4 × 4 Latin squares with a 28-day period. Experiments 1 and 2 differed in the dose of GAR (75 versus 100 g/kg DM) and GO (500 versus 750 mg/kg DM) included in the basal diet while experiment 3 was designed to compare the two doses of each additive. The results revealed that dry matter intake and rumen fluid pH were not affected by additives although organic matter (OM), neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility were slightly depressed by GO but not by GAR supplementation. MON had a similar depressing effect but was restricted mainly to ADF digestibility. Ruminal protozoa population was reduced by MON supplementation and to lesser extent by GAR100 and GO in a dose-independent manner. This effect was reflected in a lower rumen ammonia concentration. Total volatile fatty acid concentrations were not affected by any of the additives. However, individual VFAs were significantly altered by MON and to lesser extent by GAR and GO (P < 0.05), enhancing the concentration of propionate and the propionate to acetate ratio (P < 0.05). Although the capability of GAR and GO is lower than MON in decreasing the acetate to propionate ratio, they can be considered as potential alternatives to MON.