They may do so to protect their legs from biting stable flies that have their highest numbers in May and early June, according to Alberto Broce, Kansas State University livestock insect entomologist, who spoke at a beef cattle and forage program on May 3.

Stable flies are a problem not only in dairies and other confined animal feeding operations, but also reduce weight gains in pastured beef cattle, Broce said.

To avoid stable flies, cattle stomp their feet, swish tails, stand in water, rest with their legs tucked under them or bunch at corners of pastures.

Chemical controls can be applied on cattle legs but that brings only temporary relief because it is removed as cattle walk through pastures, he said.

Studies show the best control is to eliminate stable fly breeding areas. A prime site is the area where round hay bales are fed in the winter.

Cattle waste a lot of hay when eating at round-bale hay feeders, he said. This, blended with manure, moisture and mild temperatures, generates a lot of stable flies, he said.

Studies also show few stable flies originate close to the feeders that have hay and little manure.

Stable fly numbers can be cut sharply by continually moving the hay feeder, unrolling hay in different locations throughout the pasture, not unrolling poor quality or rotted hay bales that will not be eaten and avoiding feeding too much hay that promotes waste.

Source: Joplin Globe