Pasture Studies XVI the Nutritive Values of Kentucky Blue Grass, Red Top and Brome Grass

Abstract

Evidence is presented that in addition to differences in the nutritive value of different species of grasses commonly found in the pastures of Eastern Canada, the feeding value of the herbage of any single species changes during the growing season. Herbage grown during spring and fall, when plant growing conditions are favorable, is of excellent feeding value. On the contrary, herbage grown during mid-summer is of lower nutritive value, due apparently to a reduction in the availability to the animal of the carbohydrate fractions. Statistical examination of the data indicates that simple correlations between growth of the animals and the fractions of the usual feeding stuffs analysis may frequently point to erroneous conclusions when interpreted in the sense of cause and effect. Partial correlation changes not only the magnitude but also the sign of some of the coefficients. In particular it may be noted that variations in crude fiber, which under simple correlations appear important, probably actually have only minor effects on live weight gains. Also ether extract and ash are highly negatively correlated with gain. Protein content is highly correlated with gain in weight of animal. However, there is no evidence that protein as such is a limiting factor in the growth promoting value of immature pasture herbage, but rather that increases in protein probably represent merely increases in available energy.