摘要：A framework which permits estimation of economically optimal stocking rates for alternative economic parameters and alfalfa forage availability was developed and applied to a controlled grazing experiment conducted with Holstein steers (243 kg) placed on direct seeded alfalfa pastures in Central Michigan. Responses of ADG to alternative levels of forage availability per standard livestock unit (FA) were summarized by a quadratic function and the associated gains/ha were calculated. The ADG decreased as standard stocking rate (SSR; SLU/ha) increased except for the combination of the lowest observed SSR and highest FA, where ADG was curvilinear as SSR increased. The trend for gain/ha was curvilinear for all FA. The SSR which maximized gain/ha increased with FA and was greater than that which maximized ADG. Net returns to fixed resources(NRFR)/ha ($/ha)were calculated for alternative SSR and the economically optimal SSR were identified under various levels of herbage mass (kg/d). The SSR's which maximized NRFR were between the SSR's which maximized ADG and gain/ha. The magnitude of the sale price discount for heavier weight calves (slide) influenced the economically optimal SSR and the sensitivity of net return to SSR. The economically optimal SSR increased as slide increased because animals stocked under higher SSR weighed less off pasture and therefore received less price discount.
