SOFIA, Aug 6 (Reuters) - Shares in Bulgaria’s leading poultry producer Gradus opened at their issue price of 1.8 levs ($1.06) on their debut at the Bulgarian Stock Exchange on Monday, following the biggest initial public offering in the Balkan country in 10 years.

Gradus, one of Europe’s largest producer of hatching chicken eggs, raised 81 million levs in June valuing the company, at 438.5 million levs ($259.3 million).

The free float of the company is about 18 percent.