Substitution of human edible feeds with integrated use of reduced fat wheat distillers and high-quality forages in a diet for high production lactating dairy cows

This study has investigated the effect of the integration of wheat distillers, without solubles, after lipid extraction (RF-DDG) in a diet based on high-quality forages in partial substitution of human-edible feeds, i.e. corn and soybean meal (SBM), on milk production and quality, feed conversion efficiency and on the human-edible feed conversion efficiency of high producing dairy cows. The experiment was conducted on a commercial dairy farm for an 8-wk period, split into 2 periods, lasting 28 d each (2-wk adaptation and 2-wk experimental period with data collection) on 180 Holstein cows (averaging 130 DIM and 42.0kg of milk/d at the start of the trial), randomly assigned to 4 pens (45 cows each). The cows, stratified by DIM, were split in two groups assigned two diets that differed according to the human edible feed inclusion: (1) a control diet (CON), based on alfalfa silage, grass silage, high moisture ear corn silage, and soybean meal (SBM) as a protein supplement, 2) a treatment diet (TREAT), in which the control diet was modified using RF-DDG at 13.0% (dry matter basis) to totally replace soybean meal (SBM).The dry matter intake was similar across treatments, whereas the milk yield was 2.06kg/d lower for the TREAT diet. The inclusion of wheat RF-DDG increased the milk fat concentrations (3.74 vs 3.54%) and decreased the milk protein concentration (3.02 vs 3.18%), milk protein yield (1.19 vs 1.31kg/d), and milk urea nitrogen (3.63 vs 7.61mg/dL). Cows fed the TREAT diet showed an increased aNDFom, ADF ADL, NDIN and ADIN intake compared with those fed the CON diet. The TREAT diet resulted in a reduced milk yield as well as a reduced milk protein concentration and yield, which were likely caused by a reduction in the apparent digestibility of the protein and by different essential AA and RDP contents in the TREAT diet compared to the control DIET. The TREAT diet also decreased serum glucose, albumin, as well as the urea nitrogen and total protein in the blood, compared with the CON diet. Furthermore, the TREAT diet led to a reduction in the milk production feed conversion efficiency (in terms of milk yield/DMI and FPCM/DMI) and in the nitrogen utilization of the milk production (28.3 vs 31.0%). The inclusion of RF-DDG led to a substantial increase in the human-edible feed conversion index for the protein (1.19 vs. 0.74) and for energy (1.66 vs 1.39), thereby improving the net protein and energy food balance. It has been concluded that further research is needed to find an economical process to extract oil from DDG without causing any further thermal stress that could compromise the protein components and amino acid supply of RF-DDG.