WESTBROOK — Idexx Laboratories Inc, which makes diagnostic tests for livestock and poultry and tests for milk and water safety, said second-quarter profits increased 10 percent but it cut its growth outlook for the year due to currency fluctuations.

The company said earnings totaled $51.3 million, or 91 cents a share, compared with $48.7 million, or 83 cents a share a year ago. Revenue increased to $335.6 million, up from $317.9 million.

Revenues in the pet sector rose to $278.3 million, up from $259.7 million a year ago. Idexx attributed the increase to growth in its instrument and consumables business and in its reference laboratory diagnostic and consulting services business.

Revenues for water testing products in the second quarter were $22.0 million compared to $21.5 million a year ago. In the livestock and poultry diagnostics sector, revenue fell to $23.1 million compared to $25.4 million for the second quarter a year ago. Idexx said the drop in the sector’s revenues were due to lower sales of tests for Bovine Spongiform Encephalopathy, or mad cow disease, due to changes in European Union testing requirements.

For the full-year 2012, Idexx cut its outlook due to the unfavorable impact of changes in foreign currency exchange rates. It now expects full-year earnings to be in the range of $3.05 a share to $3.10 a share, down from its previous guidance in the range of $3.07 a share to $3.12 a share.

Shares of Idexx fell 4 percent to $88.85 in morning trading on Nasdaq.