Essential Oils as Dietary Supplements for Dairy Cattle

Essential oils are not required by dairy animals, but rather are compounds that have an aroma or “essence”. Some examples are allicin from garlic, thymol from thyme and oregano, capsaicin from hot peppers, eugenol from cloves, pinene from Juniper berries, limonene from dill, and cinnamonaldehyde from cinnamon, to mention a few common oils (see table). These compounds are usually an oily substance that is recovered by a steam distillation process. The most common and important activities of these compounds have been as antimicrobials and antiseptics. Medicinal properties of plants have been known for thousands of years. In recent years, many of the essential oils have been studied for these antimicrobial properties.

Essential oils are also being considered as a way to improve or alter rumen fermentation with a naturally occurring compounds rather than commercial additives or antibiotics. The objective in altering rumen fermentation is to reduce methane gas production and increase propionate and butyrate production, resulting in more efficient growth and reducing greenhouse gases. Like monensin, essential oils may affect the cell membranes of gram negative bacteria or others can act within the cell of gram positive bacteria.

Much of the research with essential oils has been done in-vitro in a controlled lab setting. The effects of oils seem to be diet and pH dependent with certain oils working better with a particular diet. There are limited data available from trials with lactating cows feeding essential oils. Whether or not the effects observed in-vitro carry over to a much larger and diverse ecosystem as a rumen is under investigation.

Tassoul and Shaver from the University of Wisconsin recently completed a trial with dairy cows pre-calving to 15 weeks into lactation. In this trial, 40 cows were used with 20 cows as control and 20 cows receiving 1.2 g of an essential oil product called CRINA. CRINA is a blend of several oils. There was not an observed benefit to the cows receiving the product prepartum. However, there was a benefit of increased fat corrected milk and dry matter intake the longer cows received the oils. It is unfortunate that the trial was discontinued after 100 days. It has been speculated that there is an adaptation time required for the oils in the rumen.

Two previous trials with lactating cows were run with the same CRINA product.

The first trial was completed in 1997 involving 33 cows with older cows in mid-lactation. The supplemented cows showed increased milk production, increased components and increased fat corrected milk yields. Cows were fed a common 50:50 forage to concentrate diet with corn silage and alfalfa as the forage. Varga and co-workers at Penn State did a production field trial involving 170 cows fed a 42:58 forage to concentrate diet where corn silage made up over 2/3 of the forage and the diet contained a fair amount of by-products. Similar results were seen in this trial with cows receiving the essential oil blend producing more milk and more fat corrected milk. Components in milk were similar but slightly higher in the treatment cows.

Is the use of essential oils recommended or justified? At the current price of about six cents per cow per day and current feed prices, we could expect about a 4 or 5:1 return if we got similar results. However, there is still a limited amount of data with controlled studies to recommend which oil or combination of oils will work with different diets. We do not fully understand their actions and mechanisms or if there are any affects on the milk that could result in wrong or inappropriate use of essential oils. We will continue to watch for further research.

Essential oils with antimicrobial activity, their main active components, and susceptible microorganisms.

Essential Oil Of	Name	Active Components	Susceptible Microorganisms	Reference
Allium sativum	Garlic	Allicin, diallyl sulfite	Enteropathogenic bacteria	Ross et al., 2001
Anethum graveolens	Dill	Limonene, carvone	Gram-positive and gram-negative bacteria	Deans and Ritchie, 1987
Capsicum annum	Paprika	Capsaicin	Gram-positive and gram-negative bacteria	Deans and Ritchie, 1987
Cynnamomum cassia	Cassia	Cinnamaldehyde	Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Salmonella enteritidis	Ouattara et al., 1997; Mahmoud, 1994; Smith-Palmer et al., 1998
Juniperus oxycedrus	Juniper	Cadinene, pinene	Aeromonas sobria, Enterococcus fecalis, Staphylococcus aureus	Hammer et al., 1999
Melaleuca alternifolia	Tea tree	Terpinen-4-ol	Staphylococcus aureus, Escherichia coli, gram-positive and gram-negative bacteria	Chao and Young, 2000; Cox et al., 2001
Origanum vulgare	Oregano	Carvacrol, thymol	Gram-positive and gram-negative bacteria	Sivropoulou et al., 1996; Dorman and Deans, 2000
Pimpinella anisum	Anise	Anethol	Aeromonas hydrophila, Brevibacterium linens, Brochothrics thermosphacta	Deans and Ritchie, 1987
Rosmarinus officinalis	Rosemary	1,8-Cineole	Staphylococcus aureus, Listeria monocytogenes, Campylobacter jejuni	Ouattara et al., 1997; Smith-Palmer et al., 1998
Syzygium aromaticum	Clove	Eugenol	Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Salmonella enteritidis, Campylobacter jejuni	Ouattara et al., 1997; Smith-Palmer et al., 1998
Thymus vulgaris	Thyme	Thymol, carvacrol	Salmonella typhimurium, Staphylococcus aureus, Aspergillus flavus	Juven et al., 1994; Ouattara et al., 1997; Mahmoud, 1994
Zingiber officinale	Ginger	Zingiberene, zingerone	Gram-positive and gram-negative bacteria	Chao and Young, 2000

By Jim Paulson, Extension Educator-Dairy
Dairy Connection Articles - University of Minnesota Dairy Extension