Description
Fescue toxicosis presents serious challenges and huge economic losses to the beef industry in the U.S. Replacing tall fescue (TF) infected by wild-type endophyte (WE) with TF infected by novel endophyte can eliminate this problem but adoption of this technology has been limited. We aimed at demonstrating the physiological and behavioral responses of heifers that grazed either WE or NE TF using relatively non-invasive techniques. Angus or Angus cross heifers (n = 24) were assigned to either WE or NE pastures for a 56-d grazing period during the summers of 2020 and 2021. Heifer ADG and hair retention scores were recorded once every 4 weeks and intravaginal temperatures were recorded for two consecutive days at this interval. Extremity temperatures were determined using thermographic imaging and hair was collected from the left rump for cortisol analysis. Animal behavior was detected using time-lapse trail cameras. The overall ADG of heifers that grazed NE was greater (p = 0.0160) compared to heifers that grazed WE in 2020, but not in 2021 (p = 0.9623). Hair retention was greater for heifers that grazed WE compared to heifers that grazed NE (p = 0.0029). Heifers that grazed WE TF had lower (p ≤ 0.0075) temperatures at ears, tails, and hooves and 0.3-0.9 °C greater intravaginal temperatures than heifers that grazed NE, especially during daytime. Hair cortisol levels of heifers that grazed WE were greater (p < 0.0001) compared to heifers that grazed NE. From 1200h-1700h each day, heifers on WE pasture spent 1.5 more (p = 0.0003) hours loafing and 0.9 fewer (p = 0.0402) hours lying down than heifers on NE pastures. These results suggest that heat stress and other physiological changes in heifers grazing WE could be mitigated by renovating pastures with NE TF.
Included in
Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Physiological and Behavioral Responses of Heifers that Graze Tall Fescue Infected by Wild-type or Novel Endophytes
Fescue toxicosis presents serious challenges and huge economic losses to the beef industry in the U.S. Replacing tall fescue (TF) infected by wild-type endophyte (WE) with TF infected by novel endophyte can eliminate this problem but adoption of this technology has been limited. We aimed at demonstrating the physiological and behavioral responses of heifers that grazed either WE or NE TF using relatively non-invasive techniques. Angus or Angus cross heifers (n = 24) were assigned to either WE or NE pastures for a 56-d grazing period during the summers of 2020 and 2021. Heifer ADG and hair retention scores were recorded once every 4 weeks and intravaginal temperatures were recorded for two consecutive days at this interval. Extremity temperatures were determined using thermographic imaging and hair was collected from the left rump for cortisol analysis. Animal behavior was detected using time-lapse trail cameras. The overall ADG of heifers that grazed NE was greater (p = 0.0160) compared to heifers that grazed WE in 2020, but not in 2021 (p = 0.9623). Hair retention was greater for heifers that grazed WE compared to heifers that grazed NE (p = 0.0029). Heifers that grazed WE TF had lower (p ≤ 0.0075) temperatures at ears, tails, and hooves and 0.3-0.9 °C greater intravaginal temperatures than heifers that grazed NE, especially during daytime. Hair cortisol levels of heifers that grazed WE were greater (p < 0.0001) compared to heifers that grazed NE. From 1200h-1700h each day, heifers on WE pasture spent 1.5 more (p = 0.0003) hours loafing and 0.9 fewer (p = 0.0402) hours lying down than heifers on NE pastures. These results suggest that heat stress and other physiological changes in heifers grazing WE could be mitigated by renovating pastures with NE TF.
