Effects of adding different levels of thyme powder and garlic cabbage powder in alfalfa, sainfoin and their mixture on digestibility and the amount of in vitro gas production

Introduction: Between 2 to 12% of a ruminant’s energy intake is typically lost through the enteric fermentation process. Ruminant production is associated with nitrogen loss especially in the form of ammonia from urine and manure management during composting. These contribute to greenhouse emission and environmental pollution in general. In the past few decades, feed additives such as antibiotics, ionophores, methane inhibitors, and anti-protozoa agents have been successfully used to reduce these rumen energy, nitrogen releases and metabolic disorders (Calsamiglia et al. 2007), though   increase production efficiency. Therefore, ruminants’ nutritionists try to use compounds that increase the efficiency of energy and protein intake by changing the population and activity of ruminal microorganisms (Fereydounpour et al. 2016).   These alternative compounds are probiotics, organic acids, and medicinal plants (Calsamiglia et al. 2007). The essential oils are secondary plant metabolites, which have antimicrobial properties and can be suitable substitutes for antibiotics to alter rumen microbial activity. Also, a research has shown that the essential oils and their constituents have the potential to improve nitrogen and energy utilization in ruminants (Patra et al. 2006). Talebzadeh et al (2012) reported that the essential oil of thyme at 150, 300, 450, and 600 micrograms per ml of culture medium was used only at concentrations above 450 mg decreased the real digestibility of organic matter. Adding powdered herbs such as thyme and garlic cabbage can affect the in vitro digestibility and the amount of in vitro gas production in sainfoin and alfalfa and their mixture. Thymol is a main phenolic component in thyme and carvacrol is also a minor component (Leung and Foster 1996). These compounds are involved in oxidation and reduction reactions. Thyroid has a large antimicrobial activity by preventing the bacteria growth. Researchers reported that active compounds in garlic containing allycine, diallylsulfide, and di-allylene sulfide, which can affect ruminal harmful bacteria. Considering the various compounds and effects of thyme and garlic and the need for further studies on medicinal plants, this study carried out to investigate the effects of adding levels of thyme powder and garlic on digestibility and fermentation parameters of sainfoin and alfalfa forage in laboratory conditions.
Material and methods: A study was conducted to investigate the effect of adding different levels   of thyme powder and garlic cabbage powder on digestibility and the amount of in vitro gas production at three levels of 0, 1.5, and 3% for alfalfa, sainfoin and mixed alfalfa and sainfoin based on a completely randomized design. Measurement of digestibility of alfalfa forage, sainfoin and mixture of 50% alfalfa and 50% sainfoin were carried out using thyme powder and garlic cabbage powder by Holden method (2000). In this method, the nylon bag was used instead of filtration and a daisy (rumen simulator) incubator was used instead of a hot water bath. Menke et al (1979) method was used to measure the amount of gas production. The amounts of short chain fatty acids, digestibility of dry matter, organic matter in dry matter, and metabolizable energy were estimated using related equations (Menke and Steinggass 1988). The data obtained from the method of gas production analyzed in a completely randomized design with repeated measurements. Data digestibility by Holden was investigated in a completely randomized design using SAS (2003) software.
Results and discussion: The results showed that adding 1.5% thyme and garlic to sainfoin forage improved digestibility of dry matter, organic matter digestibility, digestibility of organic matter in dry matter, and metabolizable energy compared with control group (P <0.05). Also, adding 3% garlic powder showed a significant increase in digestibility of organic matter in dry matter and metabolizable energy compared with the control group (P <0.05). But adding 1.5% and 3% thyme and garlic powder to alfalfa and mixed alfalfa and sainfoin had not a significant effect on dry matter digestibility, organic matter digestibility, digestibility of organic matter in dry matter and metabolizable energy compared with the control group. The results showed that adding 1.5 percent of garlic powder to sainfoin was reduced the amount of produced gas compared with the control group for 6, 24, 48 hours after incubation and also adding 3 percent of garlic powder to sainfoin was decreased the amount of produced gas compared with the control group for 6, 24, 48, 72, 96 and 120 hours after incubation (P <0.05). This trend was followed by the reduction of the amount of gas for treatment of 3% garlic + alfalfa at 3, 6, 12, 24, 48, 72, 120 times compared with the control group (P <0.05). Feeding 1.5% of garlic powder was increased the amount of produced gas at 3, 48, 72, and 120 hours of incubation compared with the control group (P <0.05). The results showed that adding 1.5 and 3% garlic powder to sainfoin forage had the lowest amount of digestible organic matter, short chain fatty acid, metabolizable energy, gas production potential and gas production rate compared with other treatments (P <0.05). Also, results showed that 3% of garlic powder in alfalfa had the lowest amount of digestible organic matter, short chain fatty acid, metabolizable energy, gas production potential compared with the control group (P <0.05). Adding plant additives had no significant effect on mixed of alfalfa and sainfoin compared with the control group. The essential oils that contain high levels of effective components (Fraser et al. 2007) or even low ones (Castillejos et al. 2006) can affect digestibility. This is due to the sensitivity of fibrolytic bacteria to the active components of all essential oils (Benchaar et al. 2007).
Conclusion: The effect of different levels of thyme and garlic on the nutritional value and digestibility of forage and sainfoin showed that addition of 1.5% of garlic and thyme improved the digestibility of forage by Holden method. Generally, adding thyme to forage at most of the times did not significantly improve the amount of gas produced compared with the control group, but at some times there was a numerical increase in the amount of produced gas. Adding 3% garlic at most of the times and 1.5% garlic at some of the times caused a significant reduction in the amount of produced gas compared with the control group. It can also be concluded that the use of 3% garlic reduced the fermentation parameters obtained from the gas test (total volatile fatty acid, metabolizable energy, and digestibility) in sainfoin and alfalfa. The results of this study suggest that the addition of thyme and garlic can change the fermentation parameters and the amount of gas production, which is different depending on their usage amount.