DOUBLECROPPED TEMPERATE AND TROPICAL CORN SILAGES FOR GROWING BEEF STEERS

Doublecropping corn (Zea mays L.) for silage will maximize forage prod uction per acre in the Coastal Plain of the southeastern USA. The prod uction and feeding value of doublecropped temperate and tropical corn hybrids were evaluated with growing beef steers. Temperate corn was ha rvested for silage on 20 July at 36.4% dry matter (DM) at 110 d after planting and the tropical corn at 23.8% DM on 11 November at 100 d aft er planting. The tropical corn produced 14% more DM/acre than did the temperate corn, Grain comprised 43.7% of the harvested DM in the tempe rate corn and 27.1% in the tropical corn. Ensiling fermentation charac teristics of the two corn hybrids were typical of well-preserved silag e. Tropical corn silage was 7.6% higher in crude protein (CP) but 20% lower in ether extract. Crude fiber, acid detergent fiber (ADF), and n eutral detergent fiber (NDF) were 29%, 31%, and 20% greater, respectiv ely, for tropical corn silage. Both silages were fed to 36 growing bee f steer calves (average initial weight 500 lb) during an 84-d feeding period. Apparent digestibilities of ADF, NDF, DM, and organic matter ( OM) were all greater for the tropical corn silage diet. Total mean ret ention time of the particulate matter in the digestive tract was longe r for steers fed the tropical corn silage, Steers fed the temperate co rn silage diet consumed 16.9% more DM/d and gained 17.6% faster (P < 0 .01) than steers fed tropical corn silage. However, DM required per un it of gain was similar for the two silage diets. Temperate and tropica l corn hybrids can be successfully doublecropped and harvested for sil age in the Coastal Plain of the USA to provide increased production pe r acre and promote expected animal body weight gains.