Interaction between plant physiology and pasture feeding value: a review
2014
Chapman, D. F. | Lee, J. M. | Waghorn, G. C.
Plant–animal interactions impact on all elements of pasture and animal performance in grazing systems. The quality of pastures for animals can be described in terms of feeding value (FV), which is a combination of feed nutritive value (NV) and voluntary intake. There are numerous complex interactions between plant physiology and pasture FV and NV. This review focuses on these interactions in four key areas (plant growth strategies, phenological development, pasture regrowth, and response to environmental stress), extracting key principles and illustrating how plant breeding or management may be used to manipulate such interactions to improve FV. The FV is low in pastures with native species that have evolved in nutrient-poor environments, especially if there are greater proportions of C4 than C3 species in the sward. Reproductive development of grasses and long grazing intervals (which affect stage of regrowth) reduce the proportion of leaf and increase stem or dead matter content in the sward. This is exacerbated by environmental stresses such as warmer temperatures and water deficit. Management decisions provide a means of manipulating many of these interactions to improve the FV of pasture, especially by improving soil nutrient status, using irrigation where possible, introducing exotic perennial pasture species such as perennial ryegrass, phalaris and tall fescue, linking the timing of grazing to stage of regrowth, and carefully managing post-grazing residual sward state. Likewise, plant breeding has focused on altering the flowering date of grasses, reducing aftermath heading, and reducing lignification within the plant to improve the FV of pasture for livestock.
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