Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2006
Publication Date: 9/20/2006
Citation: Burns, J.C., Fisher, D.S. 2006. Grazing influences on yield, nutritive value, and resistence of stockpiled jesup tall fescue without and with novel and wild type fungal endophytes. Crop Science. 46:1898-1912. Interpretive Summary: The presence of the wild type, or toxic, endophyte in tall fescue has given it stress tolerance which aids plant persistence. The wild type endophyte, however, produces alkaloids which can negatively influence daily animal responses. Recently a new tall fescue cultivar, 'Jesup' was released with greater tolerance to temperature and drought stresses. Further, a novel endophyte, that benefit the plant but does not produce toxic alkaloids, was inserted into Jesup and marketed as 'MaxQ'. This study examine the potential of MaxQ in terms of yield, nutritive value and persistence when stockpiled in the fall and initially grazed after differing periods of fall accumulation. The MaxQ tall fescue was compared to Jesup with the wild type (toxic) endophyte or with Jesup without any endophyte. In general MaxQ gave similar responses in dry matter yields and in the proportion of leaf, stem and dead tissue as did endophyte free Jesup or Jesup with the toxic endophyte. In term of nutritive value, MaxQ was similar to Jesup when free of endophyte but gave similar persistence to Jesup with the toxic endophyte. The results from this study indicate that MaxQ tall fescue would be a good choice for producers to use when establishing new tall fescue stands. Both yields and stand survival of MaxQ were as good as the toxic fescue, but nutritive value as good as Jesup without an endophyte. MaxQ appears to combine the best of both aspects without negative plant or animal consequences.
Technical Abstract: Introduction of novel endophytes in tall fescue that do not produce ergot alkaloids could potentially prevent the negative impacts of alkaloids on animal daily performance while improving plant persistence frequently associated with the presence of an endophyte. The objective of this 3-yr study was to evaluate 'Jesup' tall fescue when endophyte free, when containing a novel endophyte that does not produce ergot alkaloids, or when containing a wild type endophyte capable of producing ergot alkaloids for differences in dry matter yield, nutritive value, and stand persistence. Small paddocks were grazed to evaluate five stockpile treatments with each endophyte status after accumulating herbage from mid-August to treatment defoliation date. The treatments consisted of 1) a control (grazed each time forage reached 8-10 cm in height) or forage accumulated and grazed 2) mid-November, 3) mid-December, 4) mid-January and 5) mid-February. The endophyte status of Jesup tall fescue had no influence on total herbage mass yield, herbage mass removed when grazed, proportion of leaf, stem and dead fractions or on the nutritive value of the forage or the quantity of nutrients removed in the forage. Tall fescue stands declined for all endophyte conditions during the study with losses similar (P = 0.37) for wild type and novel endophyte stands (29.1 vs. 41.6) but were greater for the fescue without an endophyte (29.1 vs. 75.3; P = 0.01 and 41.6 vs. 75.3; P = 0.04). The length of the stockpile altered dry matter yield and nutrient components of the forage. Tall fescue yields declined linearly (from 5893 kg ha-1 for the control to 3,534 kg ha-1 by mid-February) as did in vitro true dry matter disappearance (IVTD) (from 769 to 675 g kg-1) and crude protein (from 173 to 118 g kg-1) whereas NDF increased (from 572 to 620 g kg-1). Total nonstructural carbohydrates increased and then decreased in a quadratic relationship that increased from the control (153 g kg-1) to mid-November (220 g kg-1) then declined to mid-February (107 g kg-1). Green leaf tissue averaged 62% of the tall fescue dry matter in the control and decreased linearly to 31% by the mid-February stockpiled grazing. A quadratic response occurred for green stem tissue averaging 14.3% in the control, changing little through mid-December, and then decreasing to 7.5% by mid-February, whereas dead tissue increased linearly from 24.5% to 61.4%. Green tissue (leaf and stem) IVTD was maintained and actually increased as grazing was delayed until mid-February (from 830 to 836% g kg-1 in the control to 883 to 886 by mid-February). Dead tissue had least IVTD and changed little in any of the stockpile treatments (mean = 562 g kg-1). The reduction in the nutritive value of the whole-plant tall fescue as grazing was delayed into the winter by stockpiling is attributed mainly to the large increase in dead tissue with its inherently low nutritive value. Forage with the novel endophyte present was similar in nutritive value to forage that was endophyte free and gave similar stand survival as forage that contained the wild type endophyte. These data support the use of novel endophytes in tall fescue for use in animal production systems and caution against the use of endophyte free tall fescue.