The U.S. Department of Trans­portation (DOT) last week granted a two-year waiver of the hours-of-service rule for certain drivers hauling livestock.

The rule, issued in mid-2013 by the DOT’s Federal Motor Carrier Safety Administration (FMCSA), requires truck drivers to take a 30-minute rest break for every eight hours of service. It would have prohibited drivers hauling livestock and poultry from caring for animals...