No Associative Effects Between Corn and Haycrop Silages Fed to Lactating Dairy Cows

Four first-lactation Holstein cows were used 65 to 177 days postpartum in a 4 × 4 Latin square trial to evaluate possible associative feeding effects between corn and haycrop silages. Nutrient digestibility and nitrogen and energy balances were studied. Diets were concentrate mixture, urea-treated corn silage, and early-cut, wilted haycrop silage in dry matter ratios of 55:45:0, 55:30:15, 55:15:30, and 55:0:45. Rations were offered just below energy balance in each 28-day period. Ration components were fed separately, concurrently, and twice daily. Crude protein in concentrate, corn silage, and hay crop silage dry matter was 16.9, 11.1, and 12.5%. Milk yield (18 to 19 kg) and ration dry matter intake (2.61% body weight) were not significantly different among diets. Apparent digestibility of gross energy, dry matter, protein, and fiber was not different among diets, but fat was more digestible in corn silage. Partition of ingested energy and nitrogen was not affected by treatments except that urine nitrogen was higher in corn silage. No associative feeding effects were significant. The two silages were equivalent in supporting milk production when fed in equal dry matter amounts.