The Influence of Level of Feeding and Physical Form of the Feed on the Reticulo-Rumen Fermentation in Dairy Cows Fed 12 Times Daily

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Abstract
The experiment was planned to show the effect of the physical form of the feed and the level of feeding on reticulo-rumen fermentation. The experiment followed a split-split-plot design with 8 dairy cows in the period from 6 weeks prepartum to 8 weeks post-partum. All cows were fed on 3 energy levels: 1.4, 2.8 and 4 times maintenance. The rations consisted of 57% concentrate and 43% ammonia-treated barley straw. Four of the cows were given all the straw in a long form and the other four were given half of the straw in a long and half in a ground and pelleted physical form. The composition of the concentrate was the same throughout the experiment. The cows were fed every 2 hours using an automatic feeder. Rumen fluid samples were taken at 08.00, 12.00 and 18.00 hours for determination of volatile fatty acids (VFA) content. No significant daily variations in the fermentation in the reticulo-rumen and no effect of the physical form of the feed were found, but a clear significant effect of the level of feeding was observed. The concentration of the total VFA, acetate, propionate, butyrate, valerate and ammonia increased linearly (p 0.65%), while the percentage of acetate, isobutyrate, acetate/propionate, and non-glycogenic-ratio (NGR) decreased linearly (p 0.14%) when the level of feeding increased from 1.4 to 4 times maintenance level. At the same time, the percentage of propionate increased linearly from 17 to 20% (p 0.01%) and pH decreased linearly from 6.7 to 6.0 (p 0.01%).