Westbrook-based Idexx Laboratories has posted higher first-quarter earnings and raised financial guidance for the year.

The company, which provides diagnostic tests and information for livestock and poultry and tests for the quality and safety of water and milk, also announced changes to its product distribution strategy to avoid litigation with the Federal Trade Commission.

Under the revised plan, at least one of its three national distributors of veterinary products will sell rivals’ products as well.

Idexx said in 2010 that the FTC was looking at its marketing and pricing practices.

“We believe this revised distribution arrangement satisfies the FTC concerns as we understand them,” said Idexx Chairman Jonathan Ayers in a conference call with analysts. “We believe this plan makes a lot of sense for our business and our veterinary customers and also helps us to avoid litigation with the FTC.”

First-quarter net income totaled $40.7 million, 72 cents a share, up from $36.6 million, 62 cents a share, in the first quarter of 2011. Revenue rose more than 10 percent, to $322.7 million, compared with $292.7 million a year ago.

The revenue growth was driven by higher sales of laboratory diagnostic and consulting services in the companion animal — or pet — group, which contributes most of Idexx’s sales. Idexx said it added customers with a geographical expansion.

The company had lower sales in the livestock and poultry diagnostics sector due, in part, to lower sales of mad cow disease tests.

For the full year, the company expects revenue to be in the range of $1.31 billion to $1.32 billion. Earnings are expected to be in the range of $3.07 a share to $3.12 a share, up from previous guidance of $3.04 a share to $3.10 a share.

Staff Writer Jessica Hall can be contacted at 791-6316 or at:

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