Yield, Preference, and Forage Nutritive Value of Fall-Planted Annual Grasses Under Horse Grazing at Two Maturities.

Fall-planted annual grasses can serve as alternative forage, but have not been evaluated under horse grazing.  The objectives were to evaluate annual grasses for yield, preference, and forage nutritive value under horse grazing at two maturities.  Grasses were planted August 1, 2013 and August 5, 2014 in a randomized complete block with six replicates and included spring oat, spring wheat, winter wheat, spring barley, annual ryegrass, winter rye, winter barley, and a forage variety of spring oat.  Before grazing, samples were harvested to determine yield and forage nutritive value.  Adult horses grazed three replicates for four hours at the onset of stem elongation and three replicates for four hours at the boot stage.  After grazing, horse preference was determined by visually assessing the percentage of available forage removal on a scale of 0 (no grazing) to 100 (100% grazed).  Plots were mowed and grazing was repeated when forages regrew to the target maturity.  When vegetative, winter barley, annual ryegrass, and spring forage oat yielded the most (≥4.7 t/ha), while spring barley and spring wheat yielded the least (≤3.4 t/ha; P ≤ 0.0210).  Annual ryegrass and spring wheat were the most preferred grasses with ≥69% removal, while winter barley, both spring oats, and winter rye were least preferred (≤23%; P ≤ 0.0356).  When mature, spring forage oat had a greater yield (6.5 t/ha) compared to spring wheat, winter wheat, and winter rye (≤4.2 t/ha; P ≤ 0.0357).  Spring wheat, annual ryegrass, and winter wheat were the most preferred grasses with ≥62% removal, while winter barley, spring forage oat, and winter rye were least preferred (≤20%; P ≤ 0.0498).  Although differences were observed, all annual grasses had ≤59% NDF, ≥17% CP, and ≤16% NSC.  Annual ryegrass is high yielding and highly preferred and appears to be a viable option for horse pasture.