Effects of Grinding Versus Steam-Flaking on Feeding Value of Blending Barley and Corn in Low-Forage Diets Fed to Dairy Cows

This study was carried out to evaluate the effects of processing method (grinding vs. steam-flaking) on DM intake (DMI), ruminal pH and fermentation characteristics, total digestibility of DM, and milk production of dairy cows fed blended barley and corn-based diets. Eight multiparous mid-lactation Holstein cows (88 ± 12 DIM and 44.0 ± 1.5 kg milk/d) were used in a replicated 4 × 4 Latin square design with 21-d long of each period. Cows were fed ad libitum total mixed diet consisting of 25% corn silage, 15% alfalfa hay, and 60% concentrate with equal portion of barley and corn (DM basis). Treatments were: 1) ground barley and corn (GBGC), 2) steam-flaked barley and corn (SBSC), 3) ground barley and steam-flaked corn (GBSC), and 4) steam-flaked barley and ground corn (SBGC). Data were analysed using the MIXED procedure of SAS with model including treatment as fixed effect and the random effects of square, period within square and cow within square. The PDIFF option adjusted by the Tukey method was included in the LSMEANS statement to account for multiple comparisons among treatments. Intake of DM (kg/d) tended (P < 0.06) to be less with SBSC (23.1) than other treatments (averaged 24.2). Digestibility of DM (% of intake) in the total digestive tract was greater (P < 0.04) with SBSC (73.9) and GBSC (73.4) than GBGC (70.3) and tended (P < 0.10) to be greater than SBGC (71.5). However, yield of actual milk (averaged 44.7 kg/d) and 3.5% fat corrected milk (FCM; 39.9 kg/d) as well as milk composition did not differ among treatments. Milk efficiency (milk yield/DMI) tended (P < 0.09) to be improved with SBSC (1.93) vs. GBGC (1.85) or SBGC (1.84). Ruminal pH (averaged 6.45), total VFA (averaged 125 mM), and molar proportions of individual VFA were not affected except that molar proportion of acetate tended (P < 0.06) to be greater with SBGC (58.8%) than other treatments (averaged 56.0%). Cows fed GBGC diet had sorting index below 100 for the particles retained on 19- and 8-mm sieves, indicated that cows sorted for these particles. In contrast, cows fed SBSC diet had sorting index superior to 100 for the particles retained on 19 and 8-mm sieves, thus, cows sorted against these particles. These results suggest that feeding cows with blend of steam-flaked barley and corn is beneficial to improve DM digestibility and milk efficiency.