Cultivar and Environment Effects on Annual Ryegrass Forage Yield, Yield Distribution, and Nutritive Value

Differences among annual ryegrass (Lolium multiflorum Lam.) cultivars for weight gain of grazing steers have been reported, even though plot experiments suggest that forage dry matter yield among cultivars should not be a limiting factor. Likewise, forage nutritive value differences among cultivars have not been assessed. The objectives of this research were to evaluate differences in cumulative forage yield, yield distribution, and nutritive value among 'Gulf', 'Jackson', 'Marshall', 'Rio', 'Rustmaster', and 'Surrey' annual ryegrass. Plots were harvested six times beginning in December at approximate 30-d intervals during the 1997-1998 and 1998-1999 growing seasons. Nutritive value measurements included crude protein (CP), neutral detergent fiber (NDF), in vitro true digestibility (IVTD), and digestible NDF (DNDF). There were no differences among cultivars for cumulative forage yield (P = 0.99). However, for the January harvest, Surrey and Gulf averaged 1030 (±65) kg DM ha -1 , whereas Marshall yielded only 672 (±79) kg DM ha -1 . For the March harvest, yields of all varieties were similar and averaged 1350 (±95) kg DM ha -1 . At the May harvest, Marshall and Jackson yielded 1232 (±123) kg DM ha -1 , whereas Gulf yielded only 929 (±74) kg DM ha -1 . Crude protein concentration differed significantly among harvests with a general decrease from 260 to 120 g CP kg -1 as the growing season progressed. Similar declines in nutritive value occurred for NDF, IVTD, and DNDF. Trends in yield distribution and forage quality may indicate a need for cultivar specific recommendations based on intended forage need and season of use.