Mob and rotational grazing influence pasture biomass, nutritive value, and species composition

Mob grazing, which uses very high stocking densities for short durations followed by a relatively long rest period, was designed to mimic bison (Bison bison) grazing in western U.S. grassland. This project assessed the suitability of mob grazing for livestock production in the Northeast. Objectives were to compare the effects of mob and rotational grazing on dry matter (DM) mass, nutritive value, and botanical composition across four grazing seasons. Eight, 0.10-ha paddocks were established in 2014 as a randomized complete block with four replications, and seeded with alfalfa (Medicago sativa L.), white clover (Trifolium repens L.), orchardgrass (Dactylis glomerata L.), narrowleaf plantain (Plantago lanceolata L.), and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort]. Mob-grazed (MOB) paddocks were grazed by yearling beef cattle twice each year, (70–90–day interval), and rotationally grazed (ROT) paddocks were grazed four to six times each year (when sward height reached 25 cm). Cumulative pre-grazing forage biomass (PGFM) of ROT was greater than MOB in three of four years. At the final grazing, the PGFM of ROT exceeded MOB by 2,500 kg ha⁻¹. Within year, PGFM of ROT was more consistent, varying by only 1,000–1,400 kg DM ha⁻¹ compared with 1,800–2,800 kg DM ha⁻¹ for MOB. Grazing strategy altered botanical composition; ROT favored grasses while MOB favored alfalfa. Forage fiber content was consistently lower in ROT than MOB paddocks, indicating superior nutritive value. Results suggest rotational grazing is likely suitable for more consistent forage production of greater nutritive value in temperate, cool-season grass-legume pastures of the northeastern United States.