Off-highway manufacturers reap good news.

Grain stock prices are low, construction activity is up, and the outlook remains bright for makers of agricultural and construction equipment.

The "off-highway" industry's bellwether companies - Case Corp., Caterpillar Inc. and Deere & Co. - all reported higher profits in first-quarter 1997. That's good news for the firms' Milwaukee-area suppliers, who aren't expecting business to slow down anytime soon.

"We're having an excellent year," said Jim Mitchell, chief executive officer and president of Interstate Forging Industries Inc., Milwaukee, a subsidiary of Citation Corp. of Birmingham, Ala.

Sales are up 30 percent over last year at Interstate, which forges metal for Peoria-based Caterpillar, Moline, Ill.-based Deere, and Case, which has its headquarters in Racine. And future business "looks solid in all sectors," Mitchell said.

The strength in the off-highway equipment …