Deters vampires and... flies?

Written by Darian Livingstone | Ceres Industries
(306) 653-7258 | This email address is being protected from spambots. You need JavaScript enabled to view it.

Garlic: Nature's Superfood

Garlic is becoming an increasingly trendy ingredient in livestock feed due to its acclaimed ability to deter a number of pests. By reducing the insect load on an animal, you can significantly reduce the stress that hinders the animal’s performance. Aside from being an organic pesticide, there are other benefits that garlic can have when included in your livestock diets.

A team of ruminant nutritionists working for Coop’s Agro division decided to test the theory that garlic has a minimizing effect on the number of insects that are bothering an animal. They found that not only did the garlic deter pests, but it also showed evidence of increased mineral intake. The hypothesis for the high intake is perhaps the garlic additive increases the palatability of the mineral.

So, what is it about garlic that insects don’t like?

Garlic contains an ingredient called allicin, which is released when garlic is crushed to make powder or oil. This compound, while short-lived, quickly converts to organosulphur compounds. These compounds are what exhibit the deterring effect for insects. One study suggests that garlic causes insect mortality through acetylcholinesterase inhibition. In much smaller words, this means that garlic prevents an essential enzyme from functioning in the insect’s cells. The lack of this important enzyme causes never-ending nerve impulses, resulting in rigid paralysis.

Insects will take numerous meals a day from an animal. Horn flies will take anywhere between 24 to 38. When you consider there can be up to 200 flies on a cow’s back at any given time, that is 4800 to 7600 bites a cow will endure per day. That can be a significant loss of blood over the course of a grazing season and a cow will need to partition some of her energy to make more.

A study published in the Canadian Cattlemen (2017) performed fly counts on three groups of cattle, two control groups and one fed garlic powder. The study found that fly counts were similar between all groups on June 1. Yet, the number of flies significantly declined throughout the summer in the group that was fed garlic (see Figure 1). Additionally, the garlic-fed cattle showed fewer fly avoidance behaviours – tail swishing, skin twitching – than the groups absent of garlic. These avoidance tactics distract animals and create further economic losses by disrupting grazing patterns and expending energy to avoid flies.

Average Fly Counts in Different Groups

Figure 1. The results of a study looking at the fly counts in two control groups of cattle compared to another that was supplied with bulk garlic powder mixed into common salt. The bars indicate that there was a statistical significance between the number of flies fed the garlic and the two control groups.

There have been more extensive studies surrounding the use of garlic as a pesticide conducted in the United Kingdom. Their stringent regulations pose numerous restrictions on what they can use in their agriculture practices. One of these studies has also focused on the use of garlic in crop production.

Mirzaei-Aghsaghali and his team (2012) studied effects that garlic may have on ruminants, aside from being a pest deterrent. The intention of the study was to determine how plant extracts, specifically garlic, can substitute commercial treatments in cattle such as ionophores. They also state that garlic and its extracts protect cells against free radical damage with their antioxidant properties (see Vitamin E in Equine Diets). In other studies, garlic has shown to improve cardiovascular health and immune function because of the organosulphur compounds that are released when garlic is crushed.

The primary objective of a ruminant nutritionist is to manipulate the bacteria in the rumen in a positive direction. This role has led to studies being done on the beneficial properties of garlic in the rumen as well. One characteristic that has the potential to be an excellent marketing point is garlic's ability to reduce methane gas. Pretty well everyone directly involved in agriculture understands that the impact our cattle have on the environment is minimal. In fact, the Food and Agriculture Organization has stated only 18% of total greenhouse gases (GHG) relate to livestock, directly or indirectly – indirectly being machinery use. Other sources have estimated as low as 3%.

Methanogenesis – the production of methane in the rumen – contributes to anywhere between 2 – 12% of energy losses during digestion. Sulphur compounds present in garlic inhibit methanogenesis. It also manipulates the production of certain volatile fatty acids (VFAs). Specifically, it increases the proportion of propionate and butyrate in relation to acetate. The former molecule is an essential VFA needed for the production of glucose, the primary source of energy. This shift in VFA production occurs because garlic's organosulphur compounds have an antimicrobial effect. Monensin demonstrates a very similar antimicrobial effect when fed to ruminants. Both garlic and monensin alter the microbes living within the rumen by reducing the population of bacteria that produce methane gas. Methane gas production is inefficient and leads to energy losses. So, by decreasing methanogenesis, garlic has the potential to increase feed efficiency.

Garlic can be used in all species to help to mitigate economic losses and maintain animal welfare. An article published in the Journal of Dairy Science found that the addition of garlic to feedstuffs had no influence on milk yield or cheese-making characteristics, or the yield of cheese. They found that the addition of 400 g/day of garlic did have a strong influence on the sensory attributes of milk and cheese. However, this is an incredibly high dose of garlic.

Providing livestock with Saltec Gar-lick Guard products is an economical alternative to traditional fly deterrents – ear tags or oilers – or Insect Growth Regulators (IGR) such as Altosid®. Protecting livestock from pesky, blood-sucking insects with garlic has other benefits such as better feed efficiencies. Look for the Gar-Lick Guard symbol for available products in our Saltec lineup.


Coop Agro. 2018. What’s the buzz about garlic? Agro Advisor. [blog] www.coopag.ca/wps/portal/crs/coop/ag/feed/detail/whats-the-buzz-about-garlic

Butts, M.S., Sultan, M.T., Iqbal, J.. 2009. Garlic: nature’s protection against physiological threats. Crit Rev Food Sci Nutr. 49(6): 538-551.

Eicher, S.D., Dailey, J.W.. 2002. Indicators of Acute Pain and Fly Avoidance Behaviours in Holstein Calves Following Tail-docking. J. Dairy Sci. 85: 2850-2858

EXTOXNET. 1993. Toxicology Information Brief; Cholinesterase Inhibition. A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and University of California at Davis. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program. [memo] http://pmep.cce.cornell.edu/profiles/extoxnet/TIB/cholinesterase.html accessed March 27, 2020

Furber, D. 2017. Garlic is worth its salt for fly control. Canadian Cattlemen. [blog] www.canadiancattleman.ca/2017/06/30/garlic-is-worth-its-salt-for-fly-control/

Ly, Chung. 2006. The antioxidant properties of garlic compounds: allyl cysteine, alliin, allicin, and allyl disulfide. J. Med. Food. Summer 9(2): 205-213.

Mirzaei-Aghsaghali, A. Syadati S.A., Fathi H., Rasouli S., Sadaghian M., Tarahomi M. 2012. Garlic in Ruminants Feeding. Asian J. of Bio. Sci. 5: 328-340.

Prowse, G.M. 2003. The insecticidal properties of garlic oil, with special reference to its use against two dipteran pests. University of Plymouth. Doctoral Thesis.

Rossi, G., Schiavon, S., Lomolino, G., Cupolat-Gotet, C., Simonetto, A., Bittante, G., Tagliapietra, F.. 2017. Garlic (Allium sativum L.) fed to dairy cows does not modify the cheese-making properties of milk but affects the colour, texture, and flavour of riped cheese. J. Dairy. Sci. 101: 2015-2015.