Cattle Grazing Preference among Eight Endophyte‐Free Tall Fescue Cultivars

Abstract

Abstract‘HiMag’ tall fescue (Festuca arundinacea Schreb.) was selected for high Mg concentration to reduce grass tetany risk to ruminants, but neither animal preference nor consumption of HiMag were known. The objectives were to evaluate methods of quantifying preference and to determine intake and preference by cattle (Bos taurus L.) of HiMag relative to seven other tall fescues. All entries were free of a fungal endophyte [Neotyphodium coenophialum (Morgan‐Jones & Gams) Glen, Bacon & Hanlin] that reduces cattle performance. The experimental design was a randomized complete block with three replications of eight cultivars nested within each of three test pastures. Six heifers grazed the vegetative to boot‐stage pastures for 48 h in May, June, August, and September of 1993 and 1994. The pastures, located at 1200 m elevation, were furrow irrigated. Pre‐ and postgrazed forage were clipped and weighed to determine yield and utilization (48‐h utilization< 50%) Preferencsec oringo f 0 to 10 (0 to 100% of forage eaten) was done by four trained observers at 24, 30, and 48 h. The heifers quickly learned to distinguish between cultivars, and their order of preference was Kenhy > KY 31 > HiMa=g Barcel= C1= Stargrazer > MO96 = Mozark. The cultivar × trial(year) interaction for preference indicated that cultivars responded differently to weather conditions, which in turn affected animal preference. Preference scoring had high repeatability and ranked cultivars similarly to the clip‐and‐weigh method of measuring utilization. Preference scoring was accomplished with 27% of the experimental error and only 6% of the time required for clip‐and‐weigh. Only 44% of the variation in preference score(PS) was explained by the model: PS = 8.8 ‐ 1.1(Mg DM yield ha−1). Estimated dry matter (DM) intake of HiMag was 6.4 kg (animal unit day)−1. Consumption and preference HiMag by cattle are satisfactory relative to other tall fescue cultivars.