Philip Larkin - Wires

The widest prairies have electric fences,
For though old cattle know they must not stray
Young steers are always scenting purer water
Not here but anywhere. Beyond the wires

Leads them to blunder up against the wires
Whose muscle-shredding violence gives no quarter.
Young steers become old cattle from that day,
Electric limits to their widest senses.

Philip Larkin

http://www.poemhunter.com/poem/wires/