When talking about bovine livestock, it is impossible not to think about pastures, since the main food that nature has provided, but it is curious for those who are not related to this activity to know how these plants are constituted and what they contribute to animals.
In that sense, Reyes (2007), points out that pastures are constituted by different components that are necessary for a good development and production of ruminants, among which are the following:
- Water: It is estimated that green forages are the ones that provide the highest percentage of water to the organism reaching 85 to 90% and haymade (dehydrated) and silaged forages have values between 10 to 20%. This element is fundamental in the transport of nutrients within the digestive tract to the excretions, in addition to making it possible for the animal to lose heat in hot climates through the mechanism of perspiration.
- Dry matter: it is where the nutritious elements of the fodder are concentrated, elements that the animal requires to nourish and produce; it is of vital importance for the animal's organism since it is necessary for metabolism.
- Proteins: they are the sources of amino acids and intervene in the formation of antibodies, hormones etc. In forages this varies depending on the species of grass that is in the production unit,
- Carbohydrates: they are those nutrients that provide the animal with the necessary energy, they are commonly known as sugars. Structural (cell wall) and non-structural (cell content) carbohydrates exist in grasslands.
In the same vein, Combellas (1998) explained that the quality of pastures is reflected in the contribution of nutrients necessary for the growth and development of ruminants. On the other hand, Bernal (1994), indicated that the nutritional value of forage can be evaluated by laboratory analysis or through the animal, laboratory analysis being that study of the chemical composition of the grass and the other technique used to determine the nutritional value by measuring the amount of forage consumed by the animal, excreted and used and thus determine the digestibility of the grass in the bovine.
Among the indispensable elements that grasses provide are protein and fiber, which are found in these plant species in appropriate proportions depending on the phenological state of the plant. According to Van Soest (1994), the value of 7% crude protein is the crucial point and is determined by the protein requirements of rumen microorganisms. The real value that rumen microorganisms need in terms of protein is 12%, but recycled saliva adds about 5%, so a grass with a protein content of 7% is already enough to meet the requirements. Consequently, it can be inferred that the minimum objective that should be considered is to maintain pastures with more than 7% protein in order not to affect the dry matter consumption of the animals and not thereby alter the fermentation of that forage inside the rumen.
On the other hand, when referring to Calsamiglia fiber (1997), he considered that the protein content of pastures is a determining factor in the quality of forages; but, its deficit can be solved with protein-rich supplementation such as soy. For this reason, the nutritional values of grasslands depend mainly on the consumption capacity and fiber digestibility.
It is necessary to mention that some authors point out that the quality of the pasture usually focuses on the amount of fiber that the grass has, what is fiber? fiber is the cell wall that plants have and that gives rigidity to their structures, in the composition of the cell wall there are cellulose, hemicellulose, pectin among others, in addition to lignin that is intertwined with said structural carbohydrates.
Said structural carbohydrates (Cellulose, Hemicellulose and Pectin) have significant functions in the bovine stimulating rumination (regurgitation, remastication, rensalivation and redeglution), in said process the animal produces saliva. Another substance present is lignin that, although it is useful for the plant, it has no nutritional value for the animal since it is indigestible, it limits the use of cellulose and hemicellulose when its content increases, preventing the microorganisms of the rumen from degrading it easily.
Dear readers the amount of fiber and the degree of lignification determine the nutritional value of grasses in addition to influencing the voluntary consumption of the animal, since a plant with high fiber contents affects the ruminant's ability to ingest (the animal with a few bites will begin to perform the rumination), in addition to this, if the material is lignified it will take a long time to degrade part of the forage consumed.
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| Bibliographic references |
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Reyes, J. (2007). Determination of the yield and nutritional value of grasses throughout the year for ruminant consumption in the central area of the state of Veracruz. Unpublished undergraduate work, Universidad Veracruzana, Veracruz.
Combellas, J. (1998). Alimentación de la vaca doble propósito y de sus crías. Venezuela: Fundación Inlaca.
Bernal, J. (1994). Pastures and forages. (3rd ed.). Santafé de Bogotá: Publications department of Banco ganadero.
Van soest, P. (1994). Ecological nutrition of the rumen (2nd ed). Cornell University prees.
Calsamiglia, S. (1997). New bases for the use of fiber in ruminant diets. Madrid, Spain: XIII FEDNA specialization course. Autonomous University of Barcelona.
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