Forty-four early lactation dairy cows were divided into four treatment groups to examine the effects of processed, urea-treated whole-crop wheat (pWCW), maize silage and carbohydrate supplement type to pWCW on dry matter (DM) intake and milk production. All cows received 8.5 kg/day of concentrate with cows fed the pWCW receiving an additional 2 kg/day of rolled wheat (W-pWCW) or 0.7 kg/day lactose and 1.3 kg/day rolled wheat (L-pWCW) or 2.3 kg/day of molasses (M-pWCW), whilst the maize silage (Maize) treatment received an additional 2 kg/day of rolled wheat. The pWCW or maize forages were mixed 2:1 on a DM basis with first cut grass silage and cows remained on the experimental treatments for 15 weeks. The pWCW and maize silage had a DM content of 823 and 310 g/kg, crude protein of 143 and 76 g/kg DM, and starch content of 350 and 308 g/kg DM respectively. Milk yield was similar across treatments averaging 34.3 kg/day. By contrast, milk protein concentration (g/kg) was higher (P<0.01) in cows fed M-pWCW compared with L-pWCW. There was no significant effect of treatment on milk fat content (g/kg) or fat and protein yield (kg/day). Cows fed the maize silage ate less forage than those receiving W-pWCW whilst within the pWCW treatments, those fed lactose ate less than those receiving molasses (mean values of 10.7, 13.3, 12.2 and 14.6 kg DM/day for Maize, W-pWCW, L-pWCW and M-pWCW respectively; P<0.001). There was no significant difference between treatments in average body condition score, live weight (kg) or live weight change (kg/day). There was also no significant effect of supplement to pWCW on plasma β-hydroxybutyrate concentration, whilst cows fed pWCW supplemented with molasses had the lowest plasma urea levels over the experimental period (P<0.05). In conclusion, cows fed processed, urea-treated WCW had a similar milk production to those fed good quality maize silage but consumed more forage, whilst supplementation of pWCW with lactose tended to increase milk yield and molasses increased milk protein concentration, with little effect on component yield.

Urea-treated whole-crop wheat harvested at growth stage (GS) 87 that was either unprocessed ( U) or processed ( P) by the forage harvester, and cut at one of two heights to produce a long straw ( L), or short straw ( S) forage, was offered to 44 Holstein-Friesian dairy cows for 14 weeks according to a 2 X 2 factorial design. Whole-crop wheat (WCW) was mixed 2 : 1 on a dry-matter (DM) basis with grass silage and all animals received 8.5 kg/day of concentrate and 2 kg/day of rapeseed meal. Increasing the cutting height at harvest increased the starch content in the forage from an average of 356 to 419 g/kg DM and decreased neutral-detergent fibre levels from 422 to 337 g/kg DM. Forage intake ( grass silage and WCW) was higher in cows given the unprocessed compared with the processed forages (13.7 v. 12.5 kg DM per day for treatments U v. P respectively; P < 0.05) and tended (P < 0.08) to be higher in cows given the long compared with the short straw forages. Neither processing, nor alteration of cutting height, had a significant effect on milk yield (kg/day). However, milk fat content decreased (P < 0.05) with increasing cutting height (41.9 v. 37.0 g/kg for the main effects of L v. S respectively) whilst body condition score was lower (P < 0.05) in cows given the long compared with the short straw forages (2.6 v. 2.8 respectively). Plasma glucose levels were higher (P < 0.05) in animals receiving the short compared with long straw forages (3.52 v. 3.34 mmol/l respectively) whereas beta-hydroxybutyrate decreased (P < 0.01) with increased cutting height. The average digestibility of starch in the total ration was higher (P < 0.001) in cows given the processed compared with the unprocessed WCW (0.96 v. 0.88 respectively). Assuming a constant apparent digestibility of starch in the other food components resulted in a WCW starch apparent digestibility of 0.87, 0.97, 0.80 and 0.96 for forages LU, LP, SU and SP respectively (P < 0.001). The results indicate that processing at harvest significantly increased the digestibility of starch in WCW and that cows responded to this higher nutrient content by decreasing forage intake. Increasing the cutting height at harvest decreased milk fat content (g/kg) and yield (kg/day) and increased body condition score.

It has previously been demonstrated that feeding urea treated whole crop wheat to dairy cows results in a significant increase in dry matter intake but has little effect on milk yield (Sutton et al, 1997). Part of the reason behind this lack of response has been attributed to a decrease in digestibility, particularly that of starch. A forage mill has recently been developed which allow the grains to be ground prior to ensiling and potentially increase their digestibility. An alternative way to increase the energy value of whole crop wheat is to increase cutting/stubble height. Work by Weller et al, (1995) demonstrated an increase in calculated ME from 10.6 to 11.2 MJ/kg DM by increasing stubble height from 10cm to 40cm. The objective of the current experiment was therefore to determine the effects of forage processing (grinding) and cutting height at harvest of urea-treated whole crop wheat on the intake, milk production and diet digestibility in dairy cows.