Effects of Varying Dietary Particle Size on Feeding Behavior and Digestive Function of Dairy Cattle
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Varying the particle size of feed in a dairy cow's diet has different effects on the biological function of the dairy cow, particularly feed and water intake and rumen function. Four nonpregnant, nonlactating Holstein dairy cows were fed four different dietary treatments that varied in particle size. A 4 x 4 Latin Square design was utilized to compare four different dietary treatments: long alfalfa hay, chopped alfalfa hay, corn silage, and alfalfa haylage/dry shelled cracked corn (50:50, 100% dry basis). The dietary treatments were offered ad Ii hitum for the first week (Trial I) and restricted the second week by 50% of the ad libitum intake (Trial II) in each experimental period. The variables observed and measured throughout the experiment were: particle size, daily feed intake, rumen contraction rates, activity measures, and water consumption. Statistical analyses of Trial I and Trial II were performed separately with significance declared at P< 0.1. All dietary treatments differed in average particle size distribution (P< 0.0001). Feed intake for the ad libitum and restricted periods was not affected by treatment. There was no significant effect of treatment on rumination rates in either Trial. Dietary treatment did affect free water (drinking) consumption during both the ad libitum (P< 0.002) and restricted periods (P< 0.07). Therefore, the results of this experiment show that particle size of feed does affect the dairy cow, and that particle size should be seriously considered when preparing a dairy cow's ration so that optimal performance and health will be achieved and maintained.