(Recasts, adds details, share movement)

April 23 (Reuters) - Retail farm and ranch supplies retailer Tractor Supply Co (TSCO.O: Quote, Profile, Research) posted a surprise quarterly loss due to poor sales of its expensive and seasonal items, and forecast lackluster 2008 results, sending its shares down about 7 percent.

Challenging economic conditions and a late start to spring contributed to the difficult selling environment, Chief Executive Jim Wright said in a statement.

For the first quarter, Tractor Supply posted a net loss of $1.2 million, or 3 cents a share, compared with a net profit of $5.0 million, or 12 cents a share, a year earlier.

Analysts on average had expected the company to earn 1 cent a share, before special items, according to Reuters Estimates.

Net sales rose 3 percent to $576.2 million for the quarter ended March 29. Analysts expected $610.9 million.

The company sells pet and animal products, maintenance products for agricultural and rural use and seasonal products, such as lawn and garden power equipment.

Same-store sales fell 6.5 percent partly due to one less selling day in the quarter related to the shift of the Easter holiday.

Easter fell on March 23 this year compared with April 8 last year making it the earliest Easter since 1913, according to the National Retail Federation.