Long-term Agronomic Performance and Animal Performance on Stockpiled Jessup Tall Fescue with Varying Endophyte Status.

Abstract

The objective of this study was two fold. The first objective was to evaluate the long term agronomic performance of endophyte-infected (E+), endophyte-free (E-) and novel endophyte-infected (EN) tall fescue when stockpiled and intensively grazed in the winter. The second objective was to evaluate the performance of growing cattle when intensively grazing stockpiled E+, E- and EN fescue. Stands were established in fall 1999. In August of each year plots (1 ha, 4 per trt) were harvested for hay and in early-September they were fertilized. Forage was allowed to accumulate from August until December. In December of each year, 48 Angus-cross tester cattle (4 per plot) were grazed on one of three treatments for 86 days (yr 1), 70 days (yr 2), 86 days (yr 3), 72 days (yr 4), and 56 days (yr 5). Steers were used the first year and heifers were used in subsequent years. Cattle were given a daily allotment of forage, under strip-grazing management, with a target residual height of 5cm. Total pre-graze forage mass was determined in mid-November using a falling plate meter. Forage samples were taken every two weeks. Pasture ADG of animals did not differ among the treatments (trt) (P = 0.13). Gains were 0.52, 0.59 and 0.56 kg⁄d for E+, E- and EN, respectively. Forage disappearance (DM Basis) did not differ among treatments and was 5.38, 4.41 and 4.63 kg •hd-1•d-1 (SE ± 0.24) in years 3 though 5, respectively. Endophyte-free had lower (P = 0.01) percent of total fescue (82.5%) in the sward than did the E+ (90.7%) or EN (88.4%) which did not differ (P = 0.16). Slight differences among the treatments in nutritive

composition of the sward were found. The IVTDMD of the total sward differed among treatments (P < 0.01) with having the lowest digestibility (70.7%), EN being intermediate (72.53%) and E+ being the highest (73.94%). Crude protein of the total sward was higher (P < 0.001) for the E- (11.81%) than E+ (10.86%) and EN ( 11.07%) which did not differ (P = 0.13). Endophyte status did not influence leaf senescence over the winter. Total forage mass of E- (3508 kg⁄ha) was lower than E+ (P < 0.01) and EN (P = 0.01). E+ (3979 kg⁄ha) and EN (3829 kg⁄ha) did not differ (P = 0.16). The gain per ha was higher (P = 0.01) on E+ (408.8 kg/ha) than E- (334.8 kg⁄ha). Gain per ha on EN (374.8 kg⁄ha) did not differ (P = 0.18; P = 0.12) from E+ or E-. Novel endophyte-infected fescue appears to have agronomic performance similar to E+ under these conditions. The use of stockpiled E+ as a source of low cost winter feed is a viable option for producers.