1693
Effect of Grain Type (Corn versus Milo), Particle Size (600 versus 1000 microns) and Steam-flaked Corn on Productive and Metabolite Responses of Early Lactating Holstein Cows
Ten early lactation Holstein dairy cows (5 multiparous and 5 primiparous) were used in a duplicated Latin square design to evaluate diets that differed in grain type (corn vs. milo) and grain particle size (fine vs. coarse roller-milled); a steam-flaked corn (SF-C) diet was also included for comparison. Periods were 21 d with 17 d for adaptation and 4 d for data collection, and data were subjected to mixed model analysis with contrasts used to evaluate effects of grain type, particle size, and processing method. Mean particle size of fine and coarse rolled corn, fine and coarse rolled milo and SF-C was 724, 1087, 636, 980, and 3356 microns, respectively. Daily dry matter intake was not influenced (P>0.05) by treatment (26.6, 26.6, 27.8, 26.6 and 26.4 ± 1.7 kg, respectively) nor was milk yield (41.5, 41.5, 40.5, 40.9 and 41.6 ± 3.2 kg, respectively). Treatment did not affect (P>0.05) milk component concentrations or yields except that when fed corn, cows yielded greater (P=0.03) amounts of milk protein due to numerically greater milk yield and milk protein concentration. Efficiencies of milk production, energy correct production and fat corrected production were not impacted by treatment. However, feeding corn resulted in a trend for greater (P=0.06) milk production efficiency when compared to milo. Milk urea nitrogen (MUN) was decreased (P=0.05) when feeding corn compared to milo. Similar blood glucose levels were observed pre and post feeding for all treatments. Circulating NEFA was higher (P<0.05) for rolled corn diets versus SF-C and milo diets. Period changes in body weight and body condition score were unaffected by treatment (P>0.05). Data demonstrates that rolling corn or milo to 600 or 1000 microns resulted in similar milk production and milk production efficiency as compared to SF-C. Processing corn or milo to a particle size smaller than 1000 microns did not result in increased milk production or efficiency of production suggesting that it is not necessary to reduce particle size of corn or milo below 1000 microns when included in a total mixed ration (TMR) resulting in reduced processing expense. Similar milk production and production efficiency for milo versus corn suggests that relative pricing should be utilized to determine if corn or milo should be included in lactating dairy cow diets when corn or milo is processed to a similar particle size and fed in a TMR.
Keywords: Grain processing, Particle size, Sorghum