CHICAGO, April 11 (Reuters) - Dairy farmers in the

United States are raising their defenses to try to contain the

spread of bird flu: banning visitors, cutting down trees to

discourage wild birds from landing, and disinfecting vehicles

coming onto their land.

North Carolina on Wednesday became the seventh state to

report an outbreak of highly pathogenic avian influenza (HPAI)

in a dairy herd, after the U.S. Department of Agriculture

confirmed infections in Texas, Kansas, Ohio, Michigan, Idaho and

New Mexico.

While the first cases appear to have been introduced to

herds in Texas and Kansas by wild birds, the USDA said

transmission among cattle was also possible. Agricultural

officials in Michigan and Ohio said infected herds in those

states received cattle from Texas.

Reuters spoke to seven dairy farmers in five states who said

they are reinforcing safety and cleaning procedures, with three

producers exceeding government recommendations.

"Think of our farm now as a gated community for cows," said

Karen Jordan, who raises about 200 dairy cattle in Siler City,

North Carolina. "Only the most essential person can get past the

gate."

Even before North Carolina's outbreak, Jordan, 64, said she

was limiting visitors who could unintentionally carry in

contaminated bird droppings on boots or vehicles. She also

started chopping down about 40 small trees to avoid attracting

wild birds during spring migration.

The first confirmed case in a dairy herd on March 25 and the

second human case in two years on April 1 have heightened

concerns in the U.S. about the spread of the virus to animals

and people. Bird flu has decimated poultry flocks globally since

2022 and infected mammals ranging from seals and foxes to

skunks.

The U.S. Centers for Disease Control and Prevention said

the risk to humans remains low, but has asked states for plans

to test and treat potentially impacted farm workers.

REDUCED MILK PRODUCTION

While bird flu is lethal to poultry, cows appear to recover.

The outbreaks in dairy herds primarily affect lactating cows,

the USDA said, reducing milk production and requiring farmers to

isolate sick animals while keeping their milk out of the food

supply.

U.S. milk production grew to nearly $60 billion in 2022.

Dairy farmers now fear a drop in demand for milk and cheese,

after the USDA reported bird flu in unpasteurized milk samples,

though agricultural officials say pasteurized milk is safe.

Futures prices for milk dropped as infections

expanded last week, before the market rebounded. Beef cattle

futures also plunged on fears of reduced demand, although there

have been no confirmed cases of the virus in cattle raised for

meat.

The USDA has not issued quarantine orders for infected dairy

herds but last week recommended minimizing the movement of

cattle and testing milk samples from lactating cows if they must

be moved. Producers were also urged to monitor livestock for

illnesses; isolate newly added cows; and keep wildlife and

domestic pets like cats away from farm buildings to reduce the

spread of the virus.

The agency advised farmers to pay "special attention to good

milking practices, such as equipment disinfection." In

interviews with Reuters, animal-health authorities raised the

possibility that milking machines may play a role in spreading

infections among cows, though that has not been confirmed.

"We cannot rule out other possible modes of HPAI

transmission, including equipment," the USDA said in an email to

Reuters.

Seven state and industry officials said farmers face

challenges because of uncertainty over how the virus is

spreading and the exposure of open-aired barns to wild birds.

Idaho, North Carolina and more than a dozen states that have

not confirmed cases in cattle imposed additional requirements on

shipments to protect their herds.

Nebraska, the second-biggest U.S. cattle producer after

Texas, on April 1 began requiring producers to obtain permits to

bring breeding dairy cows into the state so officials can better

track animal movement.

Texas advised producers to monitor their herds and keep

sick animals at home. Kansas recommended limiting the movement

of cattle but has not mandated extra restrictions, said Justin

Smith, the state's animal health commissioner.

"These dairies have got a lot at stake," Smith said in an

interview. "If they have concerns about that movement, they need

to reassess it, versus me mandating a reassessment."

Yogurt maker Danone said it is advising suppliers

to isolate cattle that may have been exposed to the virus and

report any cases to local officials.

DISINFECTING TIRES

In Fort Branch, Indiana, Steve Obert, 61, is requiring

drivers to spray truck wheels with disinfectant before he allows

them on his farm. He raises about 1,200 cows that produce milk

for Dairy Farmers of America, a cooperative of more than 6,000

farms.

Obert, who is also executive director of the industry group

Indiana Dairy Producers, said bigger farms face increased risks,

in part because they maintain large stocks of feed that attract

wild birds that could be carrying the virus.

Big dairies also often ship heifers, or female cows that

have not yet given birth, to other states to be impregnated

before returning to their home farms for milking, he said.

Obert, who ships cows to Kentucky, said he trusted Indiana's

decision not to impose new restrictions on cattle movement, but:

"As a producer, you sit at the edge of your seat thinking,

'Gosh, I hope we're not behind.'"

In Rockford, Illinois, 43-year-old farmer Brent Pollard, who

supplies milk to cooperative Prairie Farms, is keeping a calf he

bought for his daughter from Wisconsin in isolation for 21 days.

No cases have been reported in Wisconsin, but Shelly Mayer,

58, said she is watching for dead birds on her dairy outside

Milwaukee and working to keep water tanks clean of bird

droppings and other contaminants.

Farmers are also trying to keep wild birds away from

feed supplies but it is difficult.

"The dairy farm is like a giant bird feeder," said Jamie

Jonker, chief science officer for the National Milk Producers

Federation.