High-moisture corn was treated with a propionic acid preservative and stored in a 40,000 bushel steel bin. This corn heated and spoiled in storage and subsequently was retreated with the preservative. The out-of-condition corn was used as an ingredient in the ration for a dairy herd of cows and replacement heifers. The finished feed was cultured for fungi and assayed for mycotoxins. Results were 750,000 Fusarium spp colonies/g of feed, and 1.5 mg zearaleonone and 1.0 mg deoxynivalenol/kg of feed. Frequent episodes of behavioral estrus of 2 to 5 d duration, that were not synchronized with the ovarian cycle, were observed. Cows in the second and third trimester of pregnancy also has episodes of behavioral estrus. Idiopathic vaginitis was diagnosed. Mammary development occurred in the prepubertal heifers. Cows bred in true estrus were found in true estrus 35 to 55 d later. All of the heifers with precocious mammary development were subsequently culled from the herd because of sterility.