THE PERFORMANCE OF DAIRY-COWS OFFERED ENSILED WHOLE-CROP WHEAT, UREA-TREATED WHOLE-CROP WHEAT OR SODIUM HYDROXIDE-TREATED WHEAT-GRAIN AND WHEAT-STRAW IN A MIXTURE WITH GRASS-SILAGE

Twenty-four Holstein Friesian cows in experiment 1 and 40 cows in experiment 2 were used over 12 weeks in continuous designs, to evaluate winter wheat as a forage for daily cows. In experiment 2, whole-crop wheat was ensiled at 350 g dry mattter (DM) per kg (EW) or harvested later and stored at 550 g DM per kg following treatment with 40 g urea per kg DM (40W). In addition to these treatments in experiment 2, whole-crop wheat of 550 g DM per kg treated with 20 g urea per kg DM (20W), and combine harvested wheat grain plus wheat straw (40:60 ratio) treated with sodium hydroxide (SG) were also included. These whole-crop wheat forages were incorporated into the diet at a level of 400 g/kg of the forage DM in experiment 1, and 330 g/kg in experiment 2, with the remainder of the forage being grass silage. A control treatment of grass silage (GS) offered as the sole forage teas also included. The forages were mixed in a mixer wagon and offered ad libitum. A fixed level of 8 kg/day of concentrates was offered in experiment 1 and 7 kg/day in experiment 2. Total DM intake was significantly greater for EW and 40W than for GS in experiment 7, but not in experiment 2. Milk yield was not significant ly affected by diets (mean 28.8 kg/day in experiment 1 and 29.6 kg/day in experiment 2). Milk fat, protein and lactose contents and yields were also not significantly affected by diets. The additional fetal metabolizable energy (ME) intake of the whole-crop diets compared with GS was partitioned to live weight. There was no evidence of ME intakes being substantially greater than ME requirements as found in previous studies. A 5 X 5 Latin square digestibility experiment was carried out with Holstein-Friesian heifers offered the individual forages used in experiment 2. In take was significantly greater for the urea-treated whole-crop wheat forages than for grass silage and for sodium hydroxide-treated grain and straw. The digestible organic matter in the dry matter (DOMD) of grass silage was 692 g/kg and the whole-crop wheat diets ranged from 626 g/kg for ensiled whole-crop wheat to 682 g/kg for the sodium hydroxide-treated grain plus straw (40:60 ratio), with the DOMD of urea-treated whole-crop being intermediate. The results indicated that whole-crop wheat had higher intake characteristics than grass silage in spite of its lower digestibility.