Publication Date
1989
Description
The factors on which the digestibility of organic matter (dMO) of forages depend are now well-known. In temperate forages, this digestibility depends mainly on the growth stage, the rank of the growth-cycle, and the botanical species. It is constantly decreasing with advancing age, especially during the first growth-cycle. In aftermath growth-cycles, high temperatures accelerate the decrease of digestibility with age. Tropical forages follow the same laws, but tropical grasses are less digestible than cool-season grasses, especially at young stages and in warm weather. This is partly due to the fact that high temperatures increase cell-wall contents and lignification, and also to tropical grasses being mainly C4-plants. Dehydration and silage making modify little or not at all the digestibility of organic matter, while hay-making decreases it to quite different extents, depending on the botanical family and, above all, on the weather conditions at harvest. The nitrogen value of forages depends on their nitrogen contents which decrease with age, but also on the degradability of protein in the rumen (Deg), on the digestibility in the small intestine of the protein not degraded in the rumen (dr), and on the amount of protein synthesized by micro-organisms per kg fermented organic matter in the rumen (N/kg MOF). The Deg, dr, and N/kg MOF values adopted in France for the Feed Value Tables (INRA, 1988 and 1989) require a more accurate determination, especially as regards conserved forages. The voluntary intake of forages also decreases with age, together with digestibility. The intake of legumes decreases however less with digestibility, than does the intake of grasses. For the same digestibility, the voluntary intake of legumes is greater than that of grasses, and, at the same age, the voluntary intake of cool-season grasses is greater than that of the less digestible tropical grasses, although there exist large differences between grass species. The amount ingested can be modified to a large extent by the conditions of conservation and processing of the forages. Especially in silages, the intake may vary considerably according to length of chops, dry matter content and quality of conservation. The prediction of digestibility by laboratory methods is much more accurate than that of voluntary intake. On the other hand, there is still a lack of adequate methods for the measurement of certain parameters that determine the protein value of forages.
These gaps in knowledge have been analysed, following a systematic that there are :
- a forage or other biomass with its composition,
- a man-made technology creating an environment for the conservation process,
- the microflora, responsible for acidification or deterioration,
- methods and experimental techniques.
Citation
Zimmer, E, "Forage Conservation and Physico-Chemical Conversion" (1989). IGC Proceedings (1985-2023). 4.
(URL: https://uknowledge.uky.edu/igc/1989/openingspeeches/4)
Included in
Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Forage Conservation and Physico-Chemical Conversion
The factors on which the digestibility of organic matter (dMO) of forages depend are now well-known. In temperate forages, this digestibility depends mainly on the growth stage, the rank of the growth-cycle, and the botanical species. It is constantly decreasing with advancing age, especially during the first growth-cycle. In aftermath growth-cycles, high temperatures accelerate the decrease of digestibility with age. Tropical forages follow the same laws, but tropical grasses are less digestible than cool-season grasses, especially at young stages and in warm weather. This is partly due to the fact that high temperatures increase cell-wall contents and lignification, and also to tropical grasses being mainly C4-plants. Dehydration and silage making modify little or not at all the digestibility of organic matter, while hay-making decreases it to quite different extents, depending on the botanical family and, above all, on the weather conditions at harvest. The nitrogen value of forages depends on their nitrogen contents which decrease with age, but also on the degradability of protein in the rumen (Deg), on the digestibility in the small intestine of the protein not degraded in the rumen (dr), and on the amount of protein synthesized by micro-organisms per kg fermented organic matter in the rumen (N/kg MOF). The Deg, dr, and N/kg MOF values adopted in France for the Feed Value Tables (INRA, 1988 and 1989) require a more accurate determination, especially as regards conserved forages. The voluntary intake of forages also decreases with age, together with digestibility. The intake of legumes decreases however less with digestibility, than does the intake of grasses. For the same digestibility, the voluntary intake of legumes is greater than that of grasses, and, at the same age, the voluntary intake of cool-season grasses is greater than that of the less digestible tropical grasses, although there exist large differences between grass species. The amount ingested can be modified to a large extent by the conditions of conservation and processing of the forages. Especially in silages, the intake may vary considerably according to length of chops, dry matter content and quality of conservation. The prediction of digestibility by laboratory methods is much more accurate than that of voluntary intake. On the other hand, there is still a lack of adequate methods for the measurement of certain parameters that determine the protein value of forages.
These gaps in knowledge have been analysed, following a systematic that there are :
- a forage or other biomass with its composition,
- a man-made technology creating an environment for the conservation process,
- the microflora, responsible for acidification or deterioration,
- methods and experimental techniques.
