Digestibility and apparent mineral utilization by Arabian geldings fed alfalfa, tall fescue, and Caucasian bluestem

Three palatability and digestion trials were conducted with six Arabian geldings fed alfalfa (Medicago sativa L.), endophyte-free tall fescue (Festuca arundinacea Schreb.), and Caucasian bluestem (Bothriochloa caucasica (Trin.) C.E. Hubbard) as hay to determine nutritional value of the hays for horses at maintenance in a Latin Square designed experiment. Alfalfa had higher (P < .01) dry matter digestibility, and voluntary intake, compared to grasses. Tall fescue and Caucasian bluestem did not differ in dry matter digestibility and voluntary intake. Feeding alfalfa resulted in higher (P < .05) intake and digestibility of CP and higher (P < .05) apparent absorption of Ca, P, K, and S, compared to the grass hays. Tall fescue was higher (P < .01) in CP concentration and digestibility, total nonstructural carbohydrate concentration, and apparent absorption of Mg and S, compared to Caucasian bluestem. Caucasian bluestem was higher (P < .05) in Zn compared to tall fescue. At the end of the palatability trials, horses fed alfalfa had higher serum concentrations of blood urea nitrogen, vitamin A, and serum P, S, and Cu, compared to horses fed grasses. Serum Zn was higher (P < .05) and Se tended to be higher (P < .06) in horses fed Caucasian bluestem, compared to tall fescue. All forages were below the recommended dietary Cu and P concentration but only Caucasian bluestem resulted in negative apparent P absorption. Caucasian bluestem would meet most nutrient requirements for horses at maintenance. Alfalfa supplied more crude protein, Ca, Mg, and K than was required by horses at maintenance.