Let's talk about defoliation of grasses
Dear readers, the productive response of a bovine to grazing is closely related to the consumption of nutrients, which is determined by the biomass concentration and the quality of the pasture, since the nutritional requirements that should be supplied daily to the animal according to Rodríguez Gutiérrez and Rodríguez (2010), are proteins, carbohydrates, fats, minerals and vitamins.
In Venezuela, there are a wide variety of introduced forage species, among which stands out for example the Guinea grass (Megathyrsus maximus) which is a promising species for tropical areas, this guinea grass is a grass that by the way it regrows, by the size of the leaf blade and the leaf-stem ratio, is a species that can produce a considerable amount of edible biomass.
In this sense, in order to ensure that pastures such as guinea obtain optimal yields, it is necessary that they receive adequate agronomic and zootechnical management, since according to Perozo, González and Ortega (2009), production and productivity levels on livestock farms are directly related to the degree of technology applied in the production of pastures and forage crops, this with the purpose of achieving a balance in dry matter yield throughout their productive cycles.
Among the managements that should be considered is the frequency and height of defoliation of grasses, since, in addition to feeding the animal, their leaves have as their main function to intercept solar radiation, but apart from that, they must create mechanisms to adapt to the effect of severe defoliations, because growth tissue and carbohydrate reserves can be lost to help regrowth.
In this regard, Chacón (2013), pointed out that the impact of defoliation is determined by the amount and type of tissue removed, remaining leaf area, harvest frequency and physiological state of the pasture, likewise the author mentions that the immediate effect of a defoliation is reflected in the reduction of the leaf area and therefore less amount of intercepted light which influences the accumulation of carbohydrate reserves and root growth.
In this sense, Herrera (2006), states that some symptoms have been observed such as a decrease in the accumulation of forage in wooded species such as Megathyrsus maximus, referring to the density and growth of the stem, stating that the accumulation of biomass will depend on the cutting height. Taking into account that in the wooded species the biomass production could be affected by the cutting height, it is necessary to highlight that among the predominant grasses of the Southern Zone of Lake Maracaibo of erect and overgrown bearing is the Megathyrsus maximus as reported by (Rodríguez, 2013).
Therefore, from agrotecnia we consider that defoliation is an important disturbance factor in forage grass species, especially in those with erect-tillered growth, therefore it is important to establish height and frequency of cutting in order to prevent their growth and development from being affected, since severe defoliation results in a decrease in biomass yield.
| Final considerations |
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Dear readers, this type of pasture management can contribute from the technical point of view to the zootechnical management of tufted pastures, since different heights and frequencies of defoliation could be evaluated on any established pasture and observe whether or not changes occur on the growth, development and biomass yield variables, depending on the intensity of defoliation that the pasture is subjected.
| Bibliographic references |
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- Rodríguez, J.; Gutiérrez, R. and Rodríguez, H. (2010). Dynamics of grazing systems. Mexico: Trillas.
- Perozo, A.; González, B. and Ortega A. (2009). Effect of grazing pressure and strategic supplementation on the dry matter composition of tanner grass (Brachiaria arrecta) before and after grazing. Rev. Fac. Agron LUZ, 26, 39-58.
- Chacón, E. (2013). Principles of management and use of tropical pastures for the production of milk and grazing meat. In F. GIRARZ, Management of tropical grasses and forages (pp. 21-31). Maracaibo: Astro Data S.A.
- Herrera, R. (2006). Growth and development. In Institute of animal science, Physiology, biomass production and silvopastoral systems in tropical pastures (pp. 53-70). Havana: Institute of Animal science.
- RodrÍguez, Á. (2013). Grassland management practices and milk productivity in the Lake Maracaibo basin. In F. GIRARZ, Management of tropical grasses and forages (pp.105-115). Maracaibo: Astro Data S.A.
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