Effect of Astragalus mollissimus on Ruminal Fermentation, Methane Production and Performance of Sheep.

Recent studies have shown the anti-methanogenic capacity of Astragalus mollissimus (AM), a plant found in semiarid environments, which is known to produce 3-nitro-1-propionic acid (3NPA) and 3-nitropropanol (3NPOH). However, little is known about the effects of direct supplementation in basal diets, given that it is also known to cause cattle poisoning by nitro toxins in rangelands. In the present study, two experiments were carried out to determine CH₄ and volatile fatty acid production, animal performance and the presence of nitrocompounds in blood. In Experiment 1, four Pelibuey sheep (BW 52.8 ± 6.05 kg) were assigned to a 4 × 4 Latin square arrangement. In Experiment 2, 20 Dorper sheep were randomized to five treatments. In both experiments, AM was supplemented and fully homogenized into diets consisting of 67% oat hay and 33% concentrate. The supplementation with different amounts of AM reduces (p ≤ 0.05) the total gas and methane production. Methane was reduced by 60% when 1 g AM kg^-1 BW day^-1 was supplemented. No effects (p > 0.05) were observed in feed consumption and average daily gain. However, feed conversion was increased (p < 0.05) with AM supplementation. Finally, no differences (p > 0.05) were observed in nitrocompound concentration in plasma. These results demonstrate that 3NPA and 3NPOH from biological sources possess desirable anti-methanogenic properties to be considered supplementation alternatives.