Nutritive Evaluation of Summer Range Forage with Cattle

Abstract

Rumen-fistulated cattle were used to sample forage on desert shrub and sagebrush-grass type ranges. Cattle showed a marked preference for grass in comparison to browse. However, the chemical composition of the diet remained relatively constant during the period studied. Apparent digestibility of the forage for grazing cattle and feed intake was determined on each of the ranges during 3 summer months. Chromogens and lignin were used as digestion indicators. The chromogen technique appeared more reliable for studying the digestibility of summer range forage selected by cattle. Metabolizable, as well as digestible energy was determined. Urinary energy losses were small. Fistulated cattle digested some nutrients significantly less efficiently than intact animals. Digestibility and fecal excretion calculated from fecal grab samples were essentially identical to those based on total fecal collections when used with chromic oxide as an external indicator.