摘要：Two Iranian corn hybrids, Single Cross 704TM (S.C.704) and Three Way Cross 647TM (T.W.C.647) were used to evaluate the effects of hybrid and maturity on intake, milk yield and composition when corn was fed as silage in the diet of Holstein cows. Corn hybrid S.C.704 harvested at one-third milk-line and black layer (BL) while harvesting times for hybrid T.W.C.647 were at one-third and two-third milk-line maturity stages. Eight multiparous cows were used in a replicated experiment with a 4x4 Latin square design with 21-d periods. Diets containing 50% forage (67% corn silage and 33% chopped alfalfa hay) and 50%concentrate (DM basis) were fed as total mixed rations. Milk, 3.5% FCM and ECM, fat yield, protein percentage and production did not differ among treatments. Dietary treatments affected milk fat, lactose and total solids concentrations. Milk fat concentration differed among treatments and decreased with advancing stage of maturity which was significant for T.W.C.647. Dry matter intake, silage and nutrients intake were affected by treatment (P dry matter , but they produced milk more efficiently (1.43 vs. 1.28 to 1.31). Hybrid effect was only observed for lactose and total solids and no hybrid effect was observed for milk production, fat and protein content and yield. Corn silage hybrids at 37% of dietary dry matter intake did not have any major impact on dairy cattle performance and nutritive value of the hybrids harvested at one-third milk-line.
