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Twenty cows, including five fitted with rumen cannulae, were used to study the influence of corn processing and frequency of feeding on milk yield and ruminal fermentation characteristics. Cows were assigned to five treatments in a 5 x 5 Latin square experiment. Each period was 3 wk. Cows were fed 45% forage and 55% grain in a total mixed ration. Diets contained 35% corn either coarsely ground and fed once a day (1x), finely ground (FGC) fed 1x, steam-flaked (SFC) fed lx, FGC fed four times a day (4x), or SFC fed 4x. Processing of corn and frequency of feeding had no influence on dry matter intake. Digestibility of starch was increased 6 and 3 percentage units by feeding SFC corn compared with coarsely and finely ground corn, respectively. Cows fed SFC or FGC produced 4% more milk with lower fat content compared with coarsely ground corn. Increasing the feeding frequency did not improve milk fat content. The fat-corrected milk yield was not different among treatments. Feeding SFC resulted in a low acetate-to-propionate ratio in the rumen fluid than FGC. Cows fed SFC produced 45 and 115 g more milk protein per cow/d than cows fed FGC or coarse, respectively. With the value of increased milk protein observed in this study, it would be more economical to feed SFC or finely ground corn to dairy cows compared with coarse ground. The breakeven price of flaking corn in this study was 32 and 12/metric tonne compared with coarse and FGC, respectively. Based on a survey conducted by the authors, the price of flaking corn in the United States ranged between 7 to 22/metric tonne during year 2000.
Dhiman et al. (Tue,) studied this question.