New Auburn University Experimental Annual Ryegrass Cultivar Increases ADG in Steers

Forage availability in the Southeastern USA is limited during winter and supplemental feeding increases management cost. Therefore, development of a suitable cultivar with increased winter productivity would be a valuable contribution to animal agriculture. A breeding program was initiated in 2005 to improve the winter productivity of annual ryegrass. A random-mating base population was subjected to two cycles of phenotypic recurrent selection for increased biomass accumulation during winter. Cycle 2 (C₂) produced higher DM yield in winter than C₀ and C₁ in a two-year, five-location study. We conducted a grazing trial for two years in Central Alabama at Beef Cattle Unit of the E.V. Smith Research Center in Milstead, AL. Cycle 2 was compared to cvs. Gulf and Marshall at stocking rates of 1.5, 2.0, and 2.5 animals per acre, where the intermediate stocking rate is close to the optimum in the southeastern United States.  Beginning in mid January of each year, stocker weight gain, pasture productivity and forage quality were measured for four consecutive 28-day grazing periods. Due to the large number of samples, near infrared reflectance spectroscopy (NIRS) was used to predict forage quality. Cycle 2 (1.37 Kg d^-1) supported higher ADG (P=0.107) compared to Gulf (1.26 Kg d^-1) and was consistently better than Gulf and Marshall in ADG at all SR in year 2011 but there was no statistically significant difference in ADG among cultivars and cultivars × SR interaction in 2012. The higher ADG on C₂ compared to Gulf was significant (P ≤ 0.085) in January/February and February/March grazing period in 2011, showing better winter performance. The overall average ADG was higher in 2011 (1.32 Kg d^-1) than in 2012 (1.20 Kg d^-1). Gain ha^-1 for C₂ was more than Gulf and Marshall at all SR but was significantly greater (P ≤ 0.046) by 64 and 38 Kg ha^-1, respectively, at the lowest stocking rate. Available forage mass was higher (P ≤ 0.009) in C₂ than Gulf in February and March of 2011. Forage mass was greater (P ≤ 0.002) for C₂ than Gulf and Marshall by 593 and 731 Kg DM ha ^-1, respectively, at the intermediate stocking rate 2011. There were no differences in nutrient content (Protein, TNC and NDF) among cultivars and cultivar × SR interactions in any year. Cycle 2 appears to have higher ADG than Gulf and Marshall during winter months, which may be associated with higher biomass yield of C₂ during those months. Further grazing evaluations will focus on early seeding and grazing during the low forage availability months (December – February).