Influence of Level of Intake upon the Apparent Digestibility of Forages and Mixed Diets by Ruminants

A series of 33 digestion experiments was conducted in which the effect of level of intake upon the digestibility of forages and mixed diets was studied. Within the ranges of intake examined, the digestibility of fresh, green forages by wethers and of hays by steers was not affected by the level of intake. In two experiments with steers the digestibility of mixed diets markedly decreased as the level of consumption increased. However, the digestibility by steers of one of the same and two other mixed diets was not affected by the level of intake. Although the data obtained do not provide an explanation for the difference in the responses obtained, it was noted that the experiments in which digestibility was depressed by increasing intakes were those in which older animals were employed. However, the depression in digestibility of one ration was greater for younger than for older steers. Further evidence is presented to demonstrate the marked decline in the digestible energy value of first-growth forages as growth approaches maturity. Also, it was found that the very best aftermath forage has a lower digestible energy value than early-spring, first-growth forage. Limited data are presented which suggest that the TDN value of concentrates is greater when concentrates are fed with late-cut forage than with early-cut forage.