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Yield, Forage Nutritive Value, and Preference of Spring Planted Annual Grasses under Horse Grazing
Spring planted annual grasses can serve as emergency forage, but have yet to be evaluated under horse grazing. The objectives of this study were to evaluate annual grasses for yield, forage nutritive value, and preference under horse grazing. On May 8, 2013, winter wheat, annual ryegrass, barley, spring wheat, and oat were planted at 101, 39, 95, 135, and 90 kg/ha, respectively, in a completely randomized block design with eight replicates. Plot size was 1.8 x 6.7 meters. Yield and forage nutritive value was determined by hand-harvesting duplicate 51 cm2 areas to an 8 cm height. Three adult horses grazed four replicates at a time for four hours on June 18 (onset of stem elongation) and June 25, 2013 (boot stage). Horse preference was determined by visually assessing percentage of forage removal on a scale of 0 (no grazing activity) to 100 (100% of vegetation grazed). After grazing was completed, manure was removed and all plots were mowed to an 8 cm height. Time was allowed for re-growth and grazing was repeated when forages reached onset of stem elongation and boot stage on July 9 and July 11, 2013, respectively. Yield is presented as the sum of both grazing events. Oat and spring wheat yielded the highest with ≥ 3.91 t ha-1 while winter wheat yielded the least at 1.91 t ha-1 (P< 0.001). Only the preference of spring wheat was affected by plant maturity with less mature forage resulting in greater horse preference (P< 0.001). On average, winter wheat was the most preferred grass with a visual removal of 93% while oat was least preferred with a visual removal of 22%. Maturity did not affect ADF content. Spring wheat had the highest amount of ADF at 32% while winter wheat was lowest at 25% (P< 0.001). Maturity affected the CP content of all species with less mature forage resulting in greater amounts of CP (P< 0.001). On average, winter wheat had the greatest amount of CP at 24% while oat was lowest at 16%. With the exception of barley, NSC content was not affected by maturity (P< 0.001). On average, annual ryegrass had the greatest amount of NSC at 18% while spring wheat had the least at 11%. Spring wheat grazed at the onset of stem elongation appears to present a viable option for horse owners in need of emergency pasture forage.
Keywords: horse, grazing, forage