Siede Caroline, Juch Alina, Pohlmann Wiebke, Hamidi Dina, Isselstein Johannes, Komainda Martin
Department of Crop Sciences, Grassland Science, University of Goettingen, Goettingen 37075, Gerrmany.
Center of Biodiversity and Sustainable Land Use, University of Goettingen, Goettingen 37075, Germany.
Transl Anim Sci. 2025 Apr 18;9:txaf053. doi: 10.1093/tas/txaf053. eCollection 2025.
Heterogeneous extensive grassland offers herbivores a variation of potential bite items (BI) from which they can select. But there is a lack of knowledge on the relationship between the actually available (BI) and the grazed (BI) BI diversity albeit this information is essential to understand grass sward composition. We assessed the BI in the sward and the BI to evaluate the BI diversity under two grazing intensities in two seasons in the replicated long-term grazing experiment Forbioben. The BI diversity was measured pre-grazing using a modified sward stick (200 measurement points per 1-ha paddock) whereby at each point the botanical composition, phenological stage, color and height were recorded and consequently structured into BI. Herbage samples were taken for each BI and analyzed via near-infrared-reflectance spectroscopy for the concentration of crude protein (CP), acid-detergent fiber in the organic matter (ADF), in vitro digestibility of the organic matter (ivdOM) and metabolizable energy (ME) and labeled as grazed and non-grazed. For the BI diversity each cow was observed in the morning and afternoon four times, 2 min each on 1 d each season using an app for counting the bites and following video analysis to determine the composition of the BI. A reduction in growth rates during the hot and dry summer might have caused the decline of BI diversity of 25% under moderate and 22% under lenient grazing towards autumn (p < 0.0001). This also influenced the BI as in spring 50% and 53% of the BI diversity were grazed under moderate and lenient grazing, respectively. In autumn only 36% and 28% were grazed, respectively corresponding well to the generally lower herbage nutritive value of BI in autumn as the offered grassland resource changed over time and provided greater ivdOM and ME in spring compared to autumn (p < 0.0001). This shows a greater selectivity from the limited choice in autumn. All cows were able to maintain a good quality diet irrespective of grazing intensity which is underlined by the fact that the digestibility of ingested herbage was the same among the grazing intensities but greater in spring than in autumn.
异质性广阔的草原为食草动物提供了多种潜在的采食对象（BI）供其选择。然而，尽管了解草地组成的这一信息至关重要，但对于实际可利用的BI与采食的BI多样性之间的关系，我们仍缺乏认识。在重复进行的长期放牧试验Forbioben中，我们评估了两个季节、两种放牧强度下草皮中的BI以及采食的BI，以评估BI多样性。在放牧前，使用改良的草皮棒（每1公顷围场设置200个测量点）测量BI多样性，在每个测量点记录植物组成、物候期、颜色和高度，进而将其分类为BI。采集每个BI的牧草样本，通过近红外反射光谱分析粗蛋白（CP）浓度、有机物质中的酸性洗涤纤维（ADF）、有机物质的体外消化率（ivdOM）和代谢能（ME），并标记为采食和未采食。对于BI多样性，在每个季节的1天中，每天上午和下午对每头奶牛进行4次观察，每次观察2分钟，使用一款应用程序记录采食次数，并通过后续的视频分析确定BI的组成。炎热干燥的夏季生长率下降，可能导致秋季中度放牧下BI多样性下降25%，轻度放牧下下降22%（p < 0.0001）。这也影响了BI，春季中度和轻度放牧下分别有50%和53%的BI多样性被采食。秋季分别只有36%和28%被采食，这与秋季BI的牧草营养价值普遍较低相吻合，因为随着时间推移，提供的草地资源发生了变化，春季的ivdOM和ME比秋季更高（p < 0.0001）。这表明秋季奶牛在有限的选择中表现出更高的选择性。所有奶牛无论放牧强度如何都能够维持高质量的饮食，这一点体现在采食牧草的消化率在不同放牧强度下相同，但春季高于秋季这一事实上。
