Abstract
The aim of the study was to evaluate herbage dry matter intake in 16 beef cows which grazed continuously on permanent pastures within the “The Warta Estuary” National Park (Poland), using the minimally invasive method based on <em>n</em>-alkanes as markers (C<sub>29</sub>, C<sub>31</sub>, C<sub>33</sub>). Significant differences were observed in the nutritive value of herbage collected for analyses by cutting or nipping. The calculated content of energy and protein in the nipped herbage was higher: UFL by 58.1% and PDI by 50%, with a higher digestibility of nutrients. The values obtained for DM intake in pasture herbage by cows were closest to the standards when calculations were based on the C<sub>29</sub>/C<sub>32</sub> pair of <em>n</em>-alkanes. However, the best prediction of DM intake estimation from creeping bentgrass (<em>Agrostis stolonifera</em>) pasture, in agreement with the accepted energy and protein standards, was based on the proportions between alkanes C<sub>31</sub>/C<sub>32</sub>.
Highlights
The estimation of pasture herbage intake can be based on direct or indirect methods
The natural indicators occurring in feeds or added to the diet include lignin, chromogene stains, SiO2, including acid-insoluble ash (AIA), indigestible acid detergent fiber (IADF), or long-chain n-alkanes
The highest digestibility (%) of herbage DM was obtained when calculations were based on alkane
Summary
The direct method consists of weighing animals before and after grazing, determining the quantity of feed consumed and feces by weight [1] Another method is based on the use of a rising plate meter (RPM) for a determination of the height and weight of the herbage on pasture [2]. The estimation of herbage intake is based on collection of excreted feces after an indigestible marker is added to the feed or directly to the rumen. Such a marker should mix with the feed, pass through the digestive tract at the same rate as the feed, and be easy to analyze. Chemical indicators can be added to the diet, e.g. Cr2O3, Cr marked fiber, Cr-EDTA, Co-EDTA, polyethylene glycol (PEG), elements such as La, Yb, and Ce [3]
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