The effect of lemon seed essential oil on composition, chemical characteristics, and gas production parameters of alfalfa silage

Alfalfa is one of the most important forage plants, which is used in livestock feeding as hay in Iran. However, significant amounts of alfalfa nutrients are lost due to mechanical treatments during drying and storage process. The production of alfalfa silage in recent years has attracted more attention for feeding ruminants. Alfalfa is one of the forages that is difficult to ensiling, because of its high protein level and buffering capacity and low water soluble carbohydrate content, which require silage additives during ensilage. Additives with protective properties (based on organic acids) have been used to prevent mold and yeast growth in silage and increase aerobic stability. Recently, the use of aromatic plants and their products has increased due to their antifungal, antibacterial, and antioxidant effects.

This experiment was performed to investigate the effects of lemon seed essential oil (LSEO) on chemical properties and aerobic stability of alfalfa silage.

Alfalfa were harvested at flowering stage and chopped with a forage harvester to a theoretical length of 3 to 5 cm and wilted in the laboratory at 24 h. After the wilting period, a large sample of harvested alfalfa was randomly divided into three subsamples. Experimental treatments were: alfalfa without additive (control), alfalfa with 60 mg LSEO/kg (LSEO60), and alfalfa with 120 mg LSEO/kg (LSEO120). At the end of 60 days ensiling, silos were opened and immediately pH and dry matter of samples were measured and the remaining samples were stored for measuring Ash, ADF, NDF, CP and in vitro gas tests at -20o C. After opening the silos, gas production was measured by in vitro method with five replications at 2, 4, 6, 8, 12, 16, 24, 36, 48, 72, 96, and 120 hours. The data were analyzed based on a completely randomized design.

Results showed that adding the essential oil (at both levels) to alfalfa silage reduced the pH of the silage (p<0.05). Addition of LSEO to alfalfa silage (120 mg/kg) increased water soluble carbohydrate concentration (4.91%; p<0.05). Crude protein content was increased in treatments supplemented with LSEO120 (12.95%) compared with control (P<0.05). Aerobic stability was increased in LSEO treated groups compared with control(P<0.05). Adding 60 mg LSEO/kg alfalfa reduced the gas production volume compared with control (P<0.05). Overall, the obtained data indicate a positive effect of LSEO on the quality of alfalfa silage and its fermentation properties.

The results of this study showed that the addition of lemon seed essential oil to alfalfa silage increased aerobic stability of silage compared with control. Lemon seed essential oil had a significant effect on ammonia nitrogen and crude protein. Different levels of lemon essential oil decreased the pH significantly. Addition of lemon seed essential oil at high level of 120 mg/kg increased the amount of gas production and fermentation parameters of gas production.