Effect of Plant Extracts on Production, Nutrient Utilization, and Ruminal Fermentation in Dairy Cows
Posted: April 20, 2009
What can the active compounds cinnamaldahyde and eugenol found in essential oils do for your dairy cows? Currently, the cows at the Pennsylvania State dairy farm are experiencing first hand the addition of essential oils in their ration. Although the antimicrobial benefits of adding essential oils to the ration has been studied over the last several decades there are only a few animal studies that have been completed using essential oils to show the effects on digestion, rumen fermentation, milk composition, or milk production.
The need for research on essential oils stems from the increasing social concern over antibiotics use in animal agriculture. The first legal regulation of this issue occurred in the United Kingdom in January 2006 with the implementation of the growth-promoting antimicrobial feed additive ban (GPAFA). Since then there has been considerable attention toward natural alternatives to growth promotants across the globe.
Essential oils are being used in Europe and are being considered as possible feed additives in the US. Contrary to what the name suggests, essential oils are not oils. They consist solely of volatile, aromatic compounds that can be extracted from plants mainly by steam distillation. Structurally, they are variable mixtures of principally terpenoids, which are composed mainly of monoterpenes (C10) and sesquiterpenes (C15). These oils and extracts have a low molecular weight and significant antimicrobial activities.
How do they alter ruminal fermentation? After entering the rumen, essential oils have been shown to inhibit gram positive bacteria by interacting with the cell membrane and altering the membrane conformation. Overall, the reduction in gram positive bacteria reduces products such as methane and ammonia and increases gram negative bacteria products including the rumen volatile fatty acid propionate. There are other actions involving essential oils as antimicrobial mechanisms beyond the actions on the cell membrane. Another study reported the potential of essential oils to coagulate some cell constituents by denaturing proteins. Other studies have also reported the capacity of some phenolic and nonphenolic compounds of essential oils to interact with chemical groups of proteins and biologically active enzymes. The cows in Penn State’s Dairy Center are being used to evaluate the effects of certain essential oils. The current experiment will investigate the effects on milk yield, milk composition, rumen fermentation, urinary nitrogen losses, and total tract digestibility of nutrients.
Essential oils may offer a viable alternative to antibiotics, because they would not be exposed to the same consumer concerns as they are classified as generally recognized as safe (GRAS). The goal of the current research being conducted is to further deepen the knowledge and understanding of essential oils and their active compounds.
Jessica Tekippe, Graduate Assistant, Department of Dairy and Animal Science