Deer play on fenced land near Spring above a huge underground reservoir holding the natural gas supply keeping Houstonians warm this winter. The large herd also allows Houston Pipe Line Co. to receive a special agricultural valuation on its property, saving the company $400,000 in taxes it otherwise would owe Spring Independent School District. In suburban Austin, a 1,757-acre ranch owned by Michael Dell has what Travis County appraisers call a "well-managed deer herd" that reduces the ranch's market value of $74.8 million to an agriculture value of $290,000. Dell, founder of the computer company that made him the second-richest...