Effect of herbage mass on the selection and use by cattle of fine‐scale locations in a progressively grazed tropical grass pasture

Abstract

AbstractThis study quantified herbage mass and feeding behavior by animals at a fine spatial scale, in a 1.1‐ha bahiagrass (Paspalum notatum Flügge) pasture progressively (4 or 5 days) grazed by a herd of 32–33 beef cows and 8–13 calves in three seasons (spring, summer and autumn). Herbage mass was nondestructively estimated every day, using an electronic capacitance probe, at 91 fixed locations (50 cm × 50 cm; approximating a feeding station scale) along a permanent line transect. At the same time, selection and use of the individual locations by cows were measured every day, in terms of the number of visits, number of bites and residence time. Vegetation of the pasture created a trade‐off between availability (herbage mass) and quality (nitrogen concentration, dry matter digestibility) in summer and autumn but not in spring. There were always considerable location‐to‐location variations in the feeding behavior of animals; that is, some locations were not visited and bitten at all or were visited infrequently (once or twice daily) and grazed only for a short time (<10 s daily) receiving relatively few bites (<10 bites daily), whereas some locations were frequently visited (5–10 times daily) and utilized for a long period (>30 s daily) receiving many bites (>30 bites daily). Although regression analysis showed a tendency for animals to select and use locations with higher herbage mass in spring and those with lower or intermediate herbage mass in autumn as a result of the seasonally different availability–quality relationships, neither herbage mass nor herbage quality was an absolute factor determining the choice and use of locations by animals. The results show that the choice and use of fine‐scale locations by animals foraging in actual grasslands are not fully explained by major forage factors such as mass, nitrogen and digestibility.