The occurrence of the toxic endophyte in tall fescue is frequently associated with reduced nutritive value. However, the nutritive value of tall fescue was not altered by the presence of the toxic endophyte regardless of method of preservation, cultivar used, maturity at harvest, or location where grown (Table 11-1). In addition, no difference in CP concentrations resulted between endophyte free (E-) and endophyte infected (E+) tall fescue over a range of concentrations from about 100 to 172 g/kg. Moreover, when comparing rate of DMD between E- and E+ tall fescues [mean of ‘Kentucky 31' (KY-31) and ‘Kenhy'] the disappearance rate constants were both 0.056/h, with similar respective lag times of 10.0 and 9.9 h and similar NDF disappearance averaging 671 g/kg after 72 h (Fritz and Collins, 1991). The recent incorporation of novel endophytes into ‘Jesup' tall fescue (marketed as MaxQ; trademarked by Pennington Seed Co., Madison, GA, USA) and into ‘HiMag' (cultivar ArkPlus) has been evaluated in comparison with Jesup or HiMag that was E- or contained the E+ wild endophyte.1 Whether managed as pasture, hay, or stockpile, the differences in DMD, CP, and fiber fractions for Jesup (Table 11-1) generally were similar, and differences among the HiMag types when stockpiled also were similar for CP and fiber fractions. Only means for the three HiMag types were presented, averaging 133 g/kg for CP, 549 g/kg for NDF, and 311 g/kg for ADF (Kallenbach et al., 2003). Consequently, the presence or absence of the toxic or novel endophytes had little influence on estimates of nutritive value, rendering the endophyte status a moot point in that regard. Endophyte status, however, is involved in the apparent paradox between nutritive value and animal response, which is addressed below.
|Click Link to Expand|