Forage Nutritive Value, Yield, and Preference of Warm Season Grasses Grazed By Horses.

Warm season grasses have potential as alternative forages in Midwestern horse grazing systems when cool season grasses are less productive.  The objectives of this study were to determine the forage nutritive value, yield, and preference of warm season grasses under horse grazing.  Research was conducted during 2014 in Minnesota. Warm season grasses were established as monocultures in a randomized complete block design with six replicates on May 30. The varieties included ‘PCS 6010’ and ‘Summer Lovegrass’ teff, ‘Red’ Siberian millet, VNS Japanese millet, ‘PCS 2020’ sorghum sudangrass, and ‘PCS 3030’ sudangrass.  Grasses were grazed when vegetative and mature throughout July, August and September by mature horses. Horse preference was visually assessed on a scale of 0 (no grazing) to 100 (100% of grasses grazed).  Both varieties of teff had the lowest amount of NSC with 7% and 9% in the vegetative and mature stages, respectively (P ≤ 0.0059).  Grasses had similar CP (23%) when grazed at the vegetative stage.  At the mature stage, sorghum sudangrass had the greatest CP (20%), while sudangrass had the lowest (17%; P = 0.008).  Equine DE ranged from 2.1 to 2.2 Mcal/kg across maturities and grasses.  When vegetative, sudangrass and both varieties of teff had the greatest yield (≥ 5.3 t/ha), while Japanese and Siberian millet had the lowest yield (≤ 2.7 t/ha; P = 0.0001).  Sudangrass and ‘PSC 6010’ teff had the greatest yield (≥ 9.3 t/ha) while Siberian millet had the lowest yield (3.7 t/ha) when mature (P = 0.0012).   Across both maturities, sudangrass, sorghum sudangrass and teff were most preferred (≥ 44% removal) while Japanese and Siberian millet were least preferred (≤ 27%; P < 0.0001). Sudangrass and teff were high yielding and preferred and have potential to be summer forages in horse grazing systems in the Midwestern U.S.