Effect of selective consumption on voluntary intake and digestibility of tropical forages
1980
Zemmelink, G.
A review of the literature showed that levels of excess feed in intake and digestibility trials were quite variable. Nineteen forages of the species Stylosanthes guianensis, Desmodium distortum, Centrosema pubescens, Brachiaria mutica and B. decumbens were offered in diverse amounts to study the effect of level of excess feed on intake, and digestibility and digestible crude protein content of the consumed dry matter. Also intake of morphological components was measured. A discussion of statistical methods showed that the effect of level of excess feed on intake was underestimated by direct regression of intake on excess. To arrive at a correct estimate, intake should be related to the amount offered. A number of restrictions were imposed on the regression model for this relationship. For most forages, large effects were found of level of excess feed on intake. The response curves for various forages intersected so that the ranking order of forages varied with the level of excess feed. This behaviour was largely explained by selection between morphological components and stem parts. The pattern of selection was similar to that by grazing animals. It is recommended that intake of tropical forages should be measured not at one but at various levels of excess feed.
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