DIGESTIBILITY, APPARENT MINERAL ABSORPTION, AND VOLUNTARY INTAKE BY HORSES FED ALFALFA, TALL FESCUE, AND CAUCASIAN BLUESTEM

Alfalfa (Medicago sativa L.), low-endophyte (< 5%) tall fescue (Festuc a arundinacea Schreb.), and caucasian bluestem (Bothriochloa caucasica [Trin.] C.E. Hubbard) were fed as chopped hay to six Arabian geldings (BW 441 kg; SE 2) in intake and digestibility experiments to determin e nutritional value for horses at maintenance. Each experimental desig n was a replicated Latin square. Alfalfa was higher in DM and CP diges tibility, IVDMD, apparent absorption of Ca, K, and S, and voluntary in take than the grasses (P < .05). Caucasian bluestem was higher in Zn b ut was lower in CP, TNC, Mg, P, K, S, and Cu concentrations than tall fescue. Crude protein digestibility and apparent absorption of Mg, K, and S were higher (P < .05) for tall fescue than for caucasian blueste m. Geldings fed alfalfa for ad libitum intake had higher serum concent rations of vitamin A, blood urea nitrogen, P, S, and Cu than geldings fed grass hays. Serum Zn was higher (P < .05), whole blood Se tended t o be higher (P < .06), and BUN was lower (P < .05) in geldings fed cau casian bluestem than in those fed tall fescue. All forages met require ments for CP, Ca, Mg, K, and Fe when fed for ad libitum intake but wer e deficient in Cu for horses at maintenance. Caucasian bluestem was bo rderline in CP and was deficient in P but was the only forage that met the Zn requirement for the horses. Based on these results, caucasian bluestem could be a useful hay for horses but may require supplementat ion of CP and P.