ST. PAUL (AP) — Several teams of teenagers competing in Minnesota's 4-H Science of Agriculture Challenge may be the next generation of agricultural scientists in a country facing a critical shortage.

One team is developing GPS ear tags so cattle farmers can track herds from afar. Another thinks drones can protect livestock from predators. Yet another is developing a rechargeable portable warmer to prevent vaccines from freezing when dairy producers inoculate their herds in the winter.

University of Minnesota Extension is developing the challenge, which is already attracting interest from other states' 4-H programs. Minnesota 4-H director Dorothy Freeman expects it will become a national program.

A study last year by the U.S. Department of Agriculture and Purdue University found nearly 60,000 high-skilled agriculture-related jobs open up annually, but there were only about 35,000 college graduates available to fill them.