Growth rate and physiology of steers grazing tall fescue inoculated with novel endophytes

Abstract

Cattle grazing tall fescue (Festuca arundinacea Schreb.) often develop fescue toxicosis. This condition is thought to be caused by ergot alkaloids produced by the endophyte Neotyphodium coenophialum. Endophytes from wild tall fescue plants, which do not produce ergot alkaloids, were transferred into the endophyte-free tall fescue germplasm, HiMag. The novel associations also lacked the ability to produce ergot alkaloids. Our objective was to determine whether cattle grazing these novel endophyte associations showed signs of fescue toxicosis. At the Fayetteville, Arkansas location, tester steers (n = 72) were assigned to one of four pasture treatments: endophyte-free HiMag tall fescue (HiMag-); 'Kentucky-31' tall fescue infected with its native, toxic endophyte (KY+); and two novel endophyte-infected tall fescue associations, HiMag4 and HiMag9. At the Mount Vernon, Missouri location, steers (n = 54) were used to test three of the four cultivars (HiMag9 was not tested). Ergot alkaloid concentrations in the forage of HiMag4 and HiMag9 were low or undetectable. Respiration rate, rectal temperature, ADG, and hair scores were measured during the grazing period. Blood was collected via jugular venipuncture and used for prolactin, aspartate aminotransferase, alkaline phosphatase (ALP), lactate dehydrogenase (LDH), cholesterol, triglyceride, and creatinine analysis. Weight gains by steers grazing HiMag4 and HiMag9 did not differ from those of steers grazing HiMag-, but were greater than gains (P < 0.05) by steers on the KY+ treatment. Steers grazing KY+ had higher (P < 0.05) respiration rates, rectal temperatures, and hair scores than did steers grazing novel endophyte and HiMag- pastures. Prolactin, ALP, cholesterol, LDH, and triglycerides all were suppressed (P < 0.05) in steers grazing KY+ compared with steers grazing novel endophyte and HiMag- pastures. Steers grazing the novel endophyte tall fescues did not suffer from the decreased weight gains and toxicities associated with fescue toxicosis, resulting in enhanced animal production.

Patterns of heat response and adaptation on summer pasture: A comparison of heat-sensitive (Angus) and -tolerant (Romosinuano) cattle

“…Instead, they were on a novel endophyte pasture (i.e., Max Q) where the expected gain would average 0.54 kg/day (Nihsen et al, 2004). This was confirmed by our study where for the approximately 100 day that they spent on pasture, both ANG and RO breeds gained 0.54 and 0.55 kg/day, respectively.…”

Relationships among ergot alkaloids, cytochrome P450 activity, and beef steer growth

“…Fourteen days after weaning, steers were randomly assigned to a pasture of either Kentucky 31 (K31; four pastures; n = 20 steers) or HiMag4 (HM4; four pastures; n = 19 steers) for a summer grazing trial. Pastures and tall fescue cultivars were as previously described (Nihsen et al, 2004). During the post-weaning grazing trial (105 days) steers received a daily supplement (1.8 kg/day; 80% ground corn: 20% soybean meal; 12% CP).…”

Fescue toxicosis and its influence on the rumen microbiome: mitigation of production losses through clover isoflavones

“…Cattle grazing novel endophyte-infected tall fescue experience increased growth rates and increased average daily gain without reduced prolactin, increased respiration rates and rectal temperatures (Nihsen et al 2004;Beck et al 2008;Hancock and Andrae 2009). While the novel endophyte proves useful in managing and reducing fescue toxicosis, it is not always the most economical solution.…”