Feed Processing. III. Effects of Ground, Steam Heated, and Pelleted Hay, with and Without Pelleted Grain, on Milk Composition and Rumen Volatile Fatty Acid Ratios

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Abstract
In a 1st experiment, hay was ground to 3 different degrees of fineness and fed to lactating dairy cows. The per cent hay retained on Tyler sieves of Size 16 or larger was coarse, 66.9; medium, 39.8; and fine, 0.9. Only finely ground hay depressed milk fat content (4.6 to 3.9%), decreased the percentage of rumen acetic acid (68.3 to 59.2), and increased the percentage of propionic acid (16.2 to 24.6). These changes occurred within the 1st 7 weeks. In a 2nd experiment, steam heating or pelleting the medium ground hay used in Experiment I did not influence milk yield, milk composition, or rumen volatile fatty acid concentration. In a 3rd experiment, pelleted concentrates fed with pelleted medium ground hay depressed milk fat content only slightly when compared with unpelleted concentrates fed with the same hay.