Equine relative preferences regarding selected cool-season grass hays

Horse preferences for cool season grass cultivars under grazing has been described. However, preference for cool-season grass cultivars as hays has not been widely evaluated in horses, particularly the new varieties of Tall Fescue with novel endophytes designed to produce less ergovaline, the compound to which fescue toxicosis is attributed. First cutting hay was harvested in 2019 and 2020 from seven cool season grasses: Tall Fescue v. KY 31; Tall Fescue v. Bronson, endophyte free; Tall Fescue v. Texoma MaxQ, novel/non-toxic endophyte; Meadow Fescue v. Preval; Festulolium v. Spring Green; Perennial Ryegrass v. Elgon; and Orchardgrass v. Crown Royal. First cutting yield was determined on a dry weight basis. Sub-samples were analyzed for forage quality parameters and ergovaline concentrations. The effect of cultivar on mean hay yields was analyzed using a one-way ANOVA, and since the F-Value was significant (< 0.001) the least significant differences were further determined to compare yield differences among the cultivars. All three Tall Fescue cultivars, Meadow Fescue, and Festulolium had significantly greater yields than the Perennial Ryegrass and Orchardgrass (P < 0.05). All samples tested for ergovaline were below the reporting threshold of the laboratory. Subsequently, tillers of the Tall Fescue cultivars were evaluated for endophyte presence. Endophyte was detected in only 3.3 % and 16.7 % of v Bronson and Texoma MaxQ tillers, respectively. No endophyte was detected in v KY 31. To evaluate preference four mature idle horses (6 ± 1.08 yrs) were fasted 30 min prior to being in the test stalls for 30 min. First choice and weight consumed were recorded. Preference testing occurred within harvest year. Equine preference data were analyzed within year using a one-way ANOVA pairwise comparison with the Tukey-Kramer adjustment for multiple comparisons. Both forward and backward stepwise regression modelling were used to investigate proximate analyses values as potential predictors of cultivar consumption by the horses during the preference tests. The best performing model explained 36 % of the variation in cultivar consumption. Based on amounts consumed horses had similar preferences each year; the overall rank of the cultivars was very similar with only the two least preferred cultivars transposed from 2019 to 2020. Horses most preferred the lowest yielding cultivars (Perennial Ryegrass and Orchardgrass). Despite low ergovaline and endophyte content in the Tall Fescue varieties, adult horses preferred hay of other cultivars. Festulolium is an option for hay producers that balances both yield and horse preference.