Zebra stripes reduce fly attacks

By painting zebra-like stripes on cattle, feedlot owners and dairy operators may be able to reduce the effects of biting insects on their animals.

Biting flies can have dire consequences on cattle health, seriously affecting beef and milk production.

Irritation caused by biting flies reduces grazing, feeding, and bedding down time for cattle, while increasing behaviours such as head throwing, foot stamping, skin twitching and tail flicking.

As well, cattle will bunch together, which increases heat stress and risk of injury as dominant animals push for better positions in the group to avoid the flies.

The raised level of energy-wasting activity can lead to reduced weight gains in beef cattle and milk yields in dairy cattle.

At the Aichi Agricultural Research Center in Nagakute, Japan, researchers hypothesized that cows actually painted with black and white stripes could avoid biting fly attacks and show fewer fly-repelling behaviours.

Six pregnant Japanese Black cows were selected for paint treatments and included black-and-white painted stripes, black-painted stripes and no stripes. The cows were loosely tied side-by-side and the research team recorded all fly-repelling behaviours such as head throws, ear beating, leg stamping, skin twitching and tail flicking. Photos were taken on the right side of each cow at every observation of a biting fly on the body or legs.

To identify the species of flies, plastic boards covered with transparent, odourless, and colourless glue were placed on the ground around the experimental cows. The most frequent insects were stable flies, horn flies and horse flies. All of those trapped were counted from the digital photo images.

Results showed that the number of biting flies on the body and legs of the cows painted black-and-white was almost half compared to those on the cows painted with black stripes or those that received no striping at all.

In addition, there were no significant differences in the number of biting flies observed between those painted black and those not painted at all. The frequency of fly-repelling behaviours on the black-and-white cows was also lower than the agitated behaviours of the black-painted cows and the non-painted ones.

The width of the stripes was critical, and the report stated that stripes narrower than five centimetres can deter biting flies from landing. Further research also showed that spotted surfaces with a threshold diameter of 10 cm also prevented flies from landing.

The stripes were hand-painted to widths of four to five cm and were painted on the morning of each observation day.

Past studies have shown that biting flies respond strongly to linearly polarized light, but light and dark stripes on animals such as zebras and painted on the study cows reflect different polarizations of light in a way that disrupts the attractiveness of the animal to the flies.

As demonstrated by the study in Japan, flies land less often on animals as stripe width decreases. The striping of zebras’ coats are in a range where the pattern is the most disruptive to horse flies. Stripes may attract flies from a distance, but the confusion generated by the striping can lead to flies not decelerating in the terminal stages of flight and therefore not landing successfully.

The research suggested that the application of striping on cows in feedlots may be an environmentally friendly and practical way of controlling flies without the use of pesticides. The Japanese study results suggest that zebra-like stripes can reduce fly bites for both cattle and horses regardless whether the stripes are painted on or are designed on cloth clothing such as horse rugs.

The research report, “Cows painted with zebra-like striping can avoid biting fly attack,” was carried out by Kojima T., et al and published in PLOS ONE, October 2019.

The experiments were conducted in August and September 2017 and October 2018 on natural pasture at the Aichi Agricultural Research Center in Nagakute, Japan.

All painting was approved by the animal use and care committee of the research centre and each cow received all three treatments.

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