Regional differences in the fescue toxicosis response of Bos taurus cattle

Abstract

Cattle of the same breed from different regions of the USA may have altered responses to heat stress and fescue toxicosis. Angus steers from Missouri (MO ANG, n = 10, 513.6 ± 13.6 kg BW) and Oklahoma (OK ANG, n = 10, 552.8 ± 12.0 kg BW) were fed a diet containing either endophyte-infected (E+, 30 μg ergovaline/kg BW/day) or endophyte-uninfected (E-, 0 μg ergovaline/kg BW/day) tall fescue seed for 23 days. Diet treatment began on day 2. Animals were maintained at thermoneutrality (TN, 19-22 °C, days 1-8) and then exposed to heat stress (HS, cycling 26-36 °C, days 9-22). On day 23, ambient temperature was returned to TN and used as a recovery day. Feed intake (FI) was measured daily, with rectal and skin temperatures determined six times daily. Feed intake reduction from pretreatment levels was greater (P < 0.01) for E + (13.9 ± 0.9 versus 11.9 ± 0.3 kg/day) compared to E - (12.6 ± 0.9 versus 12.4 ± 0.3 kg/day) steers over the entire TN period, regardless of Angus group. During HS, E + cattle had reduced FI (P < 0.02; 6.9 ± 0.2 versus 8.4 ± 0.2 kg/day) compared to E - animals, independent of region of origin. A greater decrease in FI (P < 0.01) was observed for OK (12.1 ± 0.3 versus 6.2 ± 0.2 kg/day) compared to MO ANG (12.2 ± 0.3 versus 7.9 ± 0.2 kg/day) when ambient temperature was increased from TN to HS. On day 13 and days 15-22, OK ANG (E+) had reduced FI (P < 0.01, -2.21 kg) compared to OK ANG (E-), while there was no effect on MO ANG. From day 12 to day 22 of HS, daily minimum temperatures for ear, rump, and tail skin were less for E + (P < 0.05) when compared with E-treated steers, signifying peripheral vasoconstriction in E + animals. This was supported by reduced shoulder and lower tail temperatures (P < 0.01) for E + compared to E-treated OK ANG on the recovery day. In summary, regional differences in the response to fescue toxicosis exist, with peripheral vasomotor effects becoming most evident when animals are subjected to rapid changes in their environment.

Physiological response, function of sweat glands, and hair follicle cycling in cattle in response to fescue toxicosis and hair genotype

“…(Poole et al, 2019), heifers in the present study fed the EI diet consumed approximately 3.0 mg/d of ergovaline (approximately 7.5 µg/kg BW). Johnson et al (2015) did not observe an effect of EI (30 µg ergovaline/kg BW) on rectal temperature or maximal ST, whereas EI (5.6 µg/kg BW) increased rectal temperature, respiration rate, and ST (Eisemann et al, 2014) during heat stress in Angus steers. Al-Haidary et al (2001) observed increased rectal temperature, but no increase in ST in Herefords maintained at 31 °C and fed EI (5 µg/kg BW).…”

Alkaloid Contents in Epichloë Endophyte-Infected Elymus tangutorum Sampled along an Elevation Gradient on the Qinghai-Tibetan Plateau

“…The production of ergot alkaloids in a number of Epichloë-infected grass species, throughout the world, is responsible for mammalian toxicoses [26]. In China, endophytic fungus-infected drunken horse grass (Achnatherum inebrians) can produce ergonovine and ergine, which can lead to livestock toxicity.…”

“…The ergot alkaloid, ergovaline is responsible for "fescue toxicosis" in livestock [24,25]. The main symptoms of fescue toxicosis are reduced feed intake, excessive salivation, reduced reproductive performance, tissue necroses of the feet and tail, and high mortality [26][27][28]. The presence of peramine is a significant deterrent to feeding for the Argentine stem weevil (Listronotus bonariensis), and is viewed as a desirable alkaloid due to its insect-resistance activity.…”