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Garlic is worth its salt for fly control

Horn flies swarming on a cow's shoulder.

Feeding a little garlic powder to cattle does keep flies away and there are finally numbers to show it.

Cows that received trace mineral (TM) salt fortified with garlic powder had 52 per cent and 56 per cent fewer flies on average than the two control groups that received TM salt alone during a summer-long demonstration project at Beacon Hill Community Pasture in the boreal forest fringe of northwestern Saskatchewan.

Regional livestock specialists with the Saskatchewan Ministry of Agriculture took advantage of an opportunity that came their way last summer to start gathering hard evidence on this controversial fly-control method as part of an ongoing stock management project. Pasture manager Ed Sarrazin happened to mention that one patron had supplied garlic powder to mix with TM salt for his cattle the summer before and it seemed to really work.

Obi Durunna, regional livestock specialist at Prince Albert. photo: Supplied

Obi Durunna, regional livestock specialist at Prince Albert, says he and his counterparts on the project, Jenifer Heyden at North Battleford and Naomi Paley at York­ton, came up almost empty-handed when they started looking for information on feeding garlic powder to repel flies.

They found only one study and it showed that garlic powder at a two per cent inclusion rate with salt didn’t reduce horn fly numbers. Those are the pesky flies seemingly attached to the backs and sides of cattle by a magnetic-like field. When disturbed, horn flies lift up, but never fly away coming right back to continue feeding on the animal’s blood, taking as many as 30 meals a day until mating when the females leave to lay eggs in fresh manure.

Producer testimonials on blogspots didn’t offer solid evidence for or against this practice. Some tout the merits of garlic powder for fly control and increasing mineral intake, while others say it makes no difference at all.

The only way to know for sure would be to count the flies on cows fed garlic and on those not fed garlic in nearby pastures during the same grazing season because overall fly pressure varies from location to location and season to season.

That’s exactly what they did for this project. The treatment group of 150 pairs received TM salt mixed with garlic powder at 2.1 per cent of the weight of the TM salt starting on arrival, May 25. Control-1 was a group of 115 pairs and control-2 was a group of 150 pairs that received TM salt without garlic powder. The herds grazed in separate pastures about three kilometres apart during the demonstration period ending September 13.

Average fly counts in different groups.

The Compass Minerals plant at Unity supplied 140 bags of SIFTO-Canadian Stockman Medi-boot Trace Mineralized Stock Salt. The patron whose cattle received the garlic treatment purchased bulk garlic powder from Masterfeeds and it was hand-mixed with the TM salt at the pasture. The garlic-TM-salt mix and the plain TM salt were fed in open tubs and delivered as needed to the respective pastures.

Videos of each group were taken between 10 a.m. and 3 p.m. on June 1, July 6 and 21, August 10 and 30, and September 13. Still photos of the faces and sides of cows sampled were pulled from the videos and the Adobe Photoshop count tool was used to count flies visible in the photos. The videos were reviewed to observe fly-avoidance behaviours including bunching, tail flicks, head throws, leg stomps and side licks.

Fly counts include face flies around the eyes, mouth and muzzle, horn flies clustered on the poll, back, sides and undersides, and stable flies sticking mainly to the legs. It was easy to see that face-fly pressure was light, whereas horn flies were out in full force.

The season-long average for the cows sampled in the garlic group was 75 flies per cow. The cows sampled in the two control groups that received TM salt alone had average fly counts of 156 and 171.

On June 1, there wasn’t much difference between average fly counts for the garlic and control-1 groups. The difference became quite striking 41 days into the trial with the garlic group averaging approximately 100 fewer flies per cow than control-1 on July 6. The fly load in the garlic group peaked at the July 21 count, averaging approximately 150 flies per cow. It then dropped by about half by August 10, which coincided with the highest average counts for both control groups.

The average fly count on the cows in control-1 hovered just under 200 per cow on July 21 and August 10.

The average fly count on the cows in control-2 was just over 200 per cow in July and neared 250 per cow on August 10.

The fly count on cows in all groups decreased as fly pressure declined after August 10 to the end of the trial on September 13.

The garlic group consistently had the lowest fly count and exhibited the fewest fly-avoidance behaviours throughout the trial period.

Overall, avoidance behaviours were observed in 35 per cent of the cows in the garlic group, 55 per cent of the cows in control-1, and 48 per cent of the cows in control-2. This resulted in a statistical difference between the garlic and control-1 groups, but not between the garlic and control-2 groups, nor between the two control groups.

The avoidance observations didn’t reflect the fly-count pattern. In fact, fly avoidance was by far the highest on June 1 when fly loads were the lowest. On August 10, the average fly count on cows in both control groups was the highest of all for the trial period and yet the cows in those groups showed fewer avoidance behaviours than on August 30 when fly counts had dropped off.

Average avoidance behaviours among the cows in the garlic group declined through July 21 to August 30, but popped up slightly on September 13 as these behaviours became less frequent in the control groups.

The cattle didn’t seem to mind the taste of garlic, but neither did they go for it in a big way. Daily consumption was within the expected range, averaging 0.12 pounds of TM salt per head (cows plus calves plus bulls). TM salt consumption was 0.18 pounds and 0.15 pounds per head per day for control-1 and control-2, respectively.

The cost of the 88 pounds of garlic powder fed from May 25 to September 13 worked out to $1.46 per head. Comparatively, the cost to treat each animal with the long-acting pour-on insecticide, Cylence, would have been $1.06 per application (averaged between three millimetres per calf and 10 millimetres per cow) with a second treatment recommended three to four weeks later.

Durunna says the trial hasn’t been without a fair share of light-hearted comments about pre-seasoned steaks; however, nothing is known about the effect of feeding garlic powder for summer fly control on meat or milk products.

The next question is whether feeding garlic powder could have negative implications for animal health or if garlic’s antibiotic properties reported in human studies might apply to cattle as well.

The insect-repelling properties of garlic are attributed to alliin. Physical disturbance or wetting activates the transformation of alliin into allicin (diallyl thiosulphate).

In this project, the allicin content of the garlic powder was 1.2 per cent and no adverse health effects were observed when incorporating garlic powder at 2.1 per cent of the TM-salt weight.

All-in-all, Durunna says this project demonstrated that garlic powder is easy to feed and didn’t discourage TM salt intake, while reducing fly loads throughout the grazing season.

The team will be collecting more data this summer with a trial set to get underway using Masterfeeds’ premixed garlic-TM salt product containing five per cent garlic powder by weight. The cows will also be weighed at take-in and take-out.

For more information, contact Durunna at 306-953-2772.

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