Influence of supplementation method on forage use and grazing behavior by beef cattle grazing bluestem range.

Two 25-d trials (late summer and early winter) were conducted to determine the influence of supplementation method on forage use and grazing behavior. Fifteen ruminally and 12 esophageally fistulated steers (316 and 400 kg, respectively) were blocked by weight and assigned randomly to one of three treatments: 1) self-feeding supplement (via Calan gates) with salt as a limiting agent; 2) daily hand-feeding supplement plus salt; and 3) daily hand-feeding supplement without salt. Supplement intake was restricted to .95 kg.steer-1.d-1 with .23 and .40 kg of salt.steer-1.d-1 during summer and winter, respectively. Neither season nor supplementation method affected forage (1.64% of BW) or total (1.89% of BW) OM intake (P greater than .10). Total OM digestibility was greater (P less than .05) in the summer, in salt-supplemented steers, and when steers were self-fed supplement. Digestibility of NDF was greater (P less than .05) in the summer than in early winter, but did not differ among treatments (P greater than .10). Fluid dilution rate was greater (P less than .05) for salt-fed and self-fed steers during the summer but similar among treatments (P greater than .10) during the winter. Total VFA concentrations did not differ among treatments during summer, but were slightly greater (P = .07) in hand-fed steers during the winter. Steers fed supplements containing salt consistently displayed lower (P less than .01) acetate:propionate ratios, and self-fed steers had lower (P less than .01) acetate:propionate ratios during the summer. Ruminal ammonia concentrations did not differ (P greater than .10) among treatments and between periods.(ABSTRACT TRUNCATED AT 250 WORDS)