The growing concern for greenhouse gas emissions globally and the impact on climate change has necessitated the development of climate-smart goals to address the issue. One of such goals is the November 2021 Global Methane Pledge to reduce the 2020 methane emissions by 30% in 2030. The Innovation Center for US Dairy also indicated the target of the US dairy industry to achieve greenhouse gas neutrality as part of its 2050 environmental stewardship goals. To meet these goals, several efforts and resources are being expended with the aim of reducing the amount of greenhouse gases emitted from the different sources. One of the sources of methane (CH4), a potent greenhouse gas, is ruminant livestock production via enteric emissions and manure storage. Hence, the need for effective and sustainable strategies to reduce CH4 emissions from ruminant livestock production systems.
According to Fouts et al. (2022), some of the interventions that have been employed in enteric CH4 mitigation are reformulation of the diet by reducing the forage to concentrate ratio, improving the forage quality, increasing dietary fat content, the inclusion of feed additives like 3-Nitrooxypropanol (3-NOP), seaweeds (e.g. Asparagopsis sp), nitrate, essential oils, plant secondary metabolites like tannins, and the use of selective breeding methods like direct, indirect, and genomic selection. The selective breeding approach is a long-term intervention compared to dietary reformulation and inclusion of feed additives.
A recent study done at The Pennsylvania State University by Martins et al. (2024) evaluated the impact of including botanical feed additives in diets fed to lactating dairy cows, and the effect on their lactational performance, enteric CH4 emissions, and nutrient use efficiency. The botanicals used in this study were Capsicum oleoresin, with or without clove oil. The National Center for Biotechnology Information (2024) defines Capsicum oleoresin as an oily organic resin that is extracted from the fruit of plants like chili peppers which belong to the genus Capsicum, and it’s used as a cooking spice. The inclusion of Capsicum oleoresin in dairy and beef cattle diet has been attributed to its potential to modify rumen fermentation and increase intake based on the response of the animal’s body system to the additive (Oh et al., 2015). Clove oil contains eugenol which has wide-spectrum antimicrobial activity. The study by Martins et al. (2024) was a 10-week experiment, with 48 lactating Holstein cows (18 first lactation and 30 2+ lactation) which were assigned to 1 of 3 treatments- a basal diet (CON) without any botanicals, a basal diet supplemented with 300 mg/cow/day of Capsicum oleoresin (CAP), and a basal diet supplemented with 300 mg/cow/day of a combination of Capsicum oleoresin and clove oil (CAPCO). The botanicals (CAP and CAPCO) were included at 0.8% of the daily dry matter intake (DMI).
The results from this study showed that the CAP and CAPCO treatments had no effect on the DMI, milk yield, milk components, feed efficiency, daily CH4 emissions, blood energy markers (β-hydroxybutyrate, total fatty acids, and insulin), and total-tract apparent digestibility (apart from a tendency for a decrease in starch digestibility) of the cows that received the treatments. The authors, however, noted an increase in body weight of the cows during the last 2 weeks of the experiment. They also stated that the combination of Capsicum oleoresin and clove oil (CAPCO) decreased CH4 emission yield (CH4 per kg of DMI) and intensity (CH4 per kg of milk yield) up to 11% in the first lactation cows, while Capsicum oleoresin (CAP) increased blood haptoglobin concentration in the 2+ lactation cows (according to Naryzny & Legina 2021, the presence of haptoglobin in the blood shows the functionality of the liver and signals the onset of the destruction of red blood cells and other inflammatory processes in the body). It also improved the efficiency of energy utilization in all the cows, however, the available energy was not used for milk production or milk components but was channeled for body weight gain.
The authors noted that due to the diversity of botanicals, their impact on performance will be dependent on the type and productivity of the animal, composition of the diet, chemical composition of the botanical, inclusion rate in the diet, and the rumen environment. More research is needed to ascertain the efficacy of botanicals on rumen fermentation, CH4 emission, and lactational performance of dairy cows.
— Gift Omoruyi