Garlic for Fly Control?

You’ve probably seen testimonials from fellow farmers and ranchers who claim that feeding garlic can keep flies off their cattle. Maybe like me, you’re a bit skeptical. Could that really work?

Well, actually yes. According to Canadian research in 2017, cows fed trace mineral salt fortified with garlic powder had 52 and 56 percent fewer flies on average than the two control groups fed plain trace mineral salt.

Obi Durunna, a Prince Albert livestock specialist and his colleagues, Jenifer Heyden and Naomi Paley first looked for other research on garlic’s effectiveness as a fly deterrent. All they found was one study that showed a mixture of salt and 2 percent garlic didn’t reduce horn fly numbers. (Horn flies sit on the backs and sides of cattle and feed on their blood until mating day when they females leave to lay eggs in fresh manure.) Meanwhile, they’d also read producer testimonials that said it did work, and just as many that said it did nothing at all. With no clear answer they decided they’d run a test to find out for themselves.

They started with two groups of 150 cow calf pairs and one group of 115 pairs. Their pastures were just 3 kilometers apart to ensure that overall fly pressure would be the same. One group was given trace mineral salt mixed with 2.1% garlic powder (by weight). The other two groups (one of 150 and one of 115) were given plain trace mineral salt. Both were fed in open tubs starting .on May 25

Next, they counted flies.  Researchers took videos of each group between 10 am and 3 pm on June 1, July 6 and 21, August 10 and 30 and September 13. Then they pulled still photos of the faces and sides of the cattle from the videos and used the Adobe Photoshop count tool to count the number of flies in each photo. They also looked for the different types of flies. Stable flies stick mainly to legs, and face flies, of course, are on the face. From the videos, they could see that there were few face flies, but that horn flies were out in force.

The first count showed little difference between garlic cattle and the control groups. But 41 days later, the garlic cattle averaged about 100 fewer flies per cow than Control-1.

The average fly count on the Control-1 group was about 200 per cow. Control-2 averaged 200 per cow in July and neared 250 per cow on the August 10 count. Fly counts in all groups decreased after August 10 to the end of the trial on September 13. The garlic group had the lowest fly count and showed the fewest fly avoidance behaviors (bunching, tail flicks, head throws, leg stomps and side licks). Interestingly, avoidance behaviors were highest at the beginning of the summer and decreased over time, even though fly loads increased. Perhaps the cattle just got used to the flies or they figured out that the flies wouldn’t leave no matter what.

Do cattle like the taste of garlic?

According to researchers, the cattle didn’t seem to mind the taste of garlic, but it didn’t encourage them to eat more salt. Daily consumption was within the expected range of .12 pounds per head per day for the garlic group and .18 pounds and .15 pounds for the two control groups. All told, the garlic group ate 88 pounds of garlic powder at at cost of $1.46 per head. In comparison, the cost to treat animals with a long-acting pour-on insecticide would have been $2.12 per head total for two treatments during the summer.

All in all, Durunna says that garlic powder was easy to feed and did reduce fly loads during the grazing season.