Utilization of marigold leaves (Tagetes erecta L.) in rations and their effect on rumen enzyme activity, fermentation parameters, methane emission, and nutrient digestibility in vitro.

Objective: This study evaluated the utilization of marigold leaves (MGLs) in rations and their impact on rumen enzyme activity, fermentation parameters, methane (CH₄) emission, and nutrient digestibility in vitro.

Materials and methods: The experimental diets comprised different proportions of MGL incorporated into the dry matter (DM) rations. Experimental design: The MGL treatments in diets include 0% (MGL-0), 7% (MGL-7), and 14% (MGL-14).

Results: Results indicated that MGL-14 substantially raised (p < 0.05) the rumen parameters, including NH₃-N and microbial protein, total volatile fatty acids, acetate (C₂), propionate (C₃), butyrate (C₄), and the C₂:C₃ ratio. In contrast, the MGL-7 and MGL-14 groups experienced a noteworthy reduction (p < 0.05) in the total protozoa population. The MGL-7 and MGL-14 treatments also led to a substantial increase in the digestibility of DM, organic matter (OM), and crude fiber (CF) in the rumen. However, they also resulted in a decline (p < 0.05) in crude protein (CP) digestibility. The DM and OM total digestibilities were higher (p < 0.05) in the MGL-14 and MGL-7 groups. The utilization of MGL did not influence (p > 0.05) the ruminal enzyme activities (carboxymethyl cellulase, amylase, protease), cumulative gas production, kinetics, ruminal pH value, CH₄ and CO₂ production, total CF, and CP digestibility.

Conclusion: The utilization of MGL until 14% DM in diets can enhance ruminal fermentation parameters and nutrient digestibility in vitro without negatively affecting gas production kinetics or ruminal enzyme activities. However, it did not have any impact on CH₄ production.