Oregano oil supplementation in dairy cows increases milk production and reduces methane emissions

Key takeaway message: Supplementing oregano oil in the diet of dairy cows can improve milk production, reduce methane emissions, and maintain feed efficiency, providing a palatable alternative for improving the sustainability of livestock production.

Agricultural systems contribute to greenhouse gas (GHG) emissions, with ruminant livestock responsible for up to 14.5% of global GHG emissions, primarily via enteric methane (CH4). While carbon dioxide has a long-lasting impact on global warming, CH4 is a short-lived climate pollutant. Various methods measure CH4 emissions in cows, such as respiration chambers, face masks, and gas-flux quantification systems. Dairy cow CH4 production depends on diet composition, with higher fibre concentrations increasing emissions. Strategies to reduce enteric CH4 include seaweed, essential oils (e.g., oregano), and synthetic compounds. These approaches show promise in mitigating CH4 emissions while potentially enhancing animal health and milk quality. This study aimed to understand if adding oregano oil (OO) to cow diets can increase feed conversion efficiency, improve milk production, and reduce CH4 production.

Data collection occurred between December 2016 and August 2017. The study involved 52 dairy cows (primiparous, n=22; multiparous, n=30) to investigate the effects of adding OO to their diet. Cows were divided into three groups: one received none, one received OO for 60 days after calving, and the other received OO 21 days before calving until 60 days after calving. Factors including feed conversion efficiency, milk yield, milk composition, and CH4 emissions were measured to compare the three groups.

Key findings included:

1. Methane emissions:

Cows offered OO produced approximately 10% lower CH4 emissions per cow compared to those not offered OO. This reduction in CH4 was consistent with earlier in-vitro studies indicated that OO, and its component carvacrol, could reduce enteric methanogenesis, although differences were noted due to limitations in replicating the complex rumen microbiome in-vitro.

1. Rumen fluid and fatty acid concentrations:

Despite lower CH4 emissions, no significant differences were observed in rumen fluid composition, including volatile fatty acid levels and acetate-propionate ratios. This aligns with findings in other studies, indicating that OO supplementation does not alter rumen fermentation or microbial activity.

1. Milk yield and composition:

All milk-related parameters were greater in cows offered OO except concentrations of milk fat and milk protein, milk urea and somatic cell count. This is consistent with previous studies suggesting that OO positively influences milk production, fat synthesis, and lactose concentrations.

1. Feed conversion efficiency:

Feed intake and feed conversion efficiency did not differ between cows offered and not offered OO. Live weight and body condition score also showed no significant differences, indicating that OO supplementation is palatable and does not impact these parameters despite increased milk and protein yields during early lactation.

In summary, this study supports OO supplementation to mitigate CH4 production and increase milk yields in dairy cows without impacting feed intake, thus improving the environmental sustainability of livestock production. Further research is recommended to explore the long-term effects and practical applications of OO supplementation in dairy cow diets.

This study was carried out by Emily Hancock in fulfilment of her BSc in Agricultural and Livestock Sciences at the University of Nottingham. Emily is now working an agricultural labourer within the farming industry and has ambitions to build her career as a farm manager. Well done, Emily!

 

Summary by: Lucy Ross, Sustainability Consultant, Promar International