Effect of sorghum ergot (Claviceps africana) on the performance of steers (Bos taurus) in a feedlot

Abstract

The effect of ergot (Claviceps africana) in naturally infected sorghum was assessed in feedlot rations. Thirty-two Hereford steers (Bos taurus) in individual pens with access to shade were adapted to feedlot conditions and then offered one of four rations containing 0, 4.4, 8.8 or 17.6 mg/kg of ergot alkaloids (84% dihydroergosine, 10% dihydroelymoclavine and 6% festuclavine), equivalent to ~0, 10, 20 or 40 g/kg ergot (sclerotia/sphacelia) in the rations. These rations were withdrawn at noon on the second day because of severe hyperthermia and almost complete feed refusal in ergot-fed steers. After recovery on ergot-free rations for 5 days, treatment groups were incrementally introduced, over a further 3–12 days, to rations containing 0, 1.1, 2.2 or 4.4 mg/kg of alkaloids (~0, 2.5, 5 or 10 g/kg ergot, respectively). Relative exposure to ergot was maintained, so that the zero- (control), low-, medium- and high-ergot groups remained so. Steers were individually fed ad libitum, and water was freely available. Steers in all ergot-fed groups had significantly elevated rectal temperatures at 0800–1000 hours, even when the temperature–humidity index was only moderate (~70), and displayed other signs of hyperthermia (increased respiration rate, mouth breathing, excessive salivation and urination), as the temperature–humidity index increased to 73–79 during the day. Plasma prolactin was significantly reduced in ergot-fed groups. Voluntary feed intakes (liveweight basis) of the ergot-fed groups were significantly reduced, averaging 94, 86 and 86%, respectively, of the feed intakes of the control group. Hair coats were rough. While the control steers grew from a mean initial liveweight of 275 kg to a suitable slaughter weight of 455 kg in 17 weeks (growth rate 1.45 kg/day), ergot-fed groups gained only 0.77–1.10 kg/day and took at least 5 weeks longer to reach the slaughter weight, despite removal of ergot at the same time as control steers were sent to slaughter. Sorghum ergot, even at low concentrations (1.1 mg alkaloids/kg feed) is severely detrimental to the performance of steers in the feedlot.

Activities and Effects of Ergot Alkaloids on Livestock Physiology and Production

“…The geographic scope of this impact ranges from countries such as the United States [ 1 ], New Zealand [ 2 ], and Australia [ 3 ] that have a heavy reliance on grazing for aspects of livestock production. This impact also extends to countries such as Japan [ 4 , 5 ], Korea [ 6 ], and the United Arab Emirates [ 7 ] that import hay as a feedstuff for livestock production and maintenance and countries such as Australia that use ergot-contaminated feeds in intensive livestock production settings [ 8 , 9 ]. A substantial challenge in the elucidation of ergot alkaloid-induced effects is the highly variable individual animal response to exposure.…”

A Bird's-Eye View of Veterinary Medicine

“…Blaney et al (2009) indentified ergotamine as the dominant ergopeptine produced by Claviceps purpurea sclerotia, which is the ergot that infects Australian rye. Blaney et al (2011) reported severe hyperthermia in steers fed feedyard rations containing sorghum infected with Claviceps Africana, as compared to steers consuming non-infected sorghum.…”

Risks for animal health related to the presence of ergot alkaloids in feed

“…The CONTAM Panel derived an RP for adverse animal health effects of 0.1 mg T-EAs/kg complete feed for bovines. Blaney et al (2011) demonstrated adverse effects at 1.1 mg EAs/kg feed DM. Applying an uncertainty factor of 3 17 to deduce a NOAEL from a LOAEL, a NOAEL of 0.4 mg EAs/kg feed DM was derived.…”