Animal and Pasture Responses to Grazing Management of Chemically Suppressed Tall Fescue in Mixed Pastures

Abstract

Treatment of toxic endophyte‐infected tall fescue [Lolium arundinaceum (Schreb.) Darbysh] with metsulfuran‐methyl {Methyl 2‐[[[[(4‐methoxyl‐6‐methyl‐1,3,5‐triazin‐2‐yl)‐amino]carbonyl]amino]sulfonyl] benzoate}, as delivered by Chaparral herbicide (Dow AgroSciences, Indianapolis, IN) can mitigate fescue toxicosis and enhance forage nutritive value by suppressing seedhead emergence. A grazing experiment was conducted with steers (2013) and heifers (2014) to evaluate animal and plant responses to grazing management of mixed cool‐season grass pastures treated with Chaparral. Continuous and rotational stocking treatments were assigned to six, 3.0‐ha pastures in a randomized complete block design with three replications in 2013 and two replications in 2014. Each pasture had six tester animals, and stocking rates were varied using put‐and‐take animals. Pastures were grazed from 16 April to 8 July 2013 and 20 May to 12 Aug. 2014. Pasture carrying capacity was 20% greater for rotational than continuous stocking. Calves on rotationally stocked pastures also had 26% greater average daily gain (ADG) and body weight (BW) gain per hectare than those on the continuous treatment. Pre‐grazed herbage had less neutral detergent fiber (NDF) and acid detergent fiber (ADF) than post‐grazed herbage and herbage from continuously stocked pastures in 2013, but they did not differ in 2014. Crude protein (CP) was lower in post‐graze rotational pasture than in continuous or pre‐graze rotational pasture. Fescue roots in rotationally stocked pastures had greater water soluble carbohydrates (WSC) and N concentrations than continuously stocked pastures following the second year of grazing. Results indicated that rotational stocking of Chaparral treated mixed pastures can improve animal performance and pasture productivity.

Effects of grazing different ergovaline concentrations on vasoactivity of bovine lateral saphenous vein1

“…Fifteen, Bos taurus, predominantly Angus crossbred steers were used at the conclusion of a larger grazing study that evaluated grazing management of toxic endophyte-infected tall fescue pastures chemically treated to suppress production (Williamson et al, 2016;Williamson and Aiken, 2017). This study used 3 pastures of either bermudagrass (n = 5 steers; BW = 340.3 ± 9.3 kg), toxic endophyteinfected Kentucky-31 tall fescue untreated (n = 5 steers; BW = 300.5 ± 6.5 kg), or toxic endophyteinfected Kentucky-31 tall fescue treated (n = 5 steers; BW = 294.1 ± 9.1 kg) with Chapparal herbicide mixture (Dow AgroSciences, Indianapolis, IN) to provide 87.1 g/ha of an aminopyralid (2-pyridine carboxylic acid, 4-amino-3,6-dichloro-) and 13.2 g/ ha of metsulfuran-methyl (methyl 2- [[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-amino]carbonyl] amino]sulfonyl]benzoate) that were divided into six 3.0-ha paddocks.…”

“…Fifteen of the steers (5 steers per pasture treatment randomly selected across paddocks) from the larger grazing study described by Williamson et al (2016) and Williamson and Aiken (2017) were held on their respective treatment pastures until day of biopsy. Tall fescue tiller samples were collected on day 1 relative to the initiation of the first biopsy day.…”

“…Although there were differences in the available pasture ergovaline concentrations for steers to graze at the time of the lateral saphenous vein biopsies, there were no differences in the levels of serum prolactin or vascular wall thickness to indicate a gradation in physiological effects associated with different pasture levels of ergovaline. This could be a consequence of the seedhead-suppressed pastures containing a higher concentration of ergovaline earlier in the grazing period (Williamson et al, 2016), and those residual effects could have carried over into this biopsy portion of the study (Aiken et al, 2013;Klotz et al, 2016).…”

Ecological, biophysical and production effects of incorporating rest into grazing regimes: A global meta‐analysis

“…Continuous grazing is often considered to lead to greater weight gain as livestock are able to selectively graze preferred plants (Briske et al, ; Ellison, ; Joseph, Molinar, Galt, Valdez, & Holechek, ). In contrast, smaller grazing units under SRG can lead to greater and more uniform herbage production and utilization with consequently greater animal production per hectare (Joseph et al, ; Norton et al, ; Williamson, Aiken, Flynn, & Barrett, ). Our meta‐analyses partially support these findings, as we found no significant difference in animal weight gain between SRG and CG and greater animal production per hectare under SRG than CG.…”

Stocking method and monensin supplementation effects on cow and calf performance and pasture productivity

“…(2011) reported rotational stocking increased forage production, decreased pasture waste, and improved pasture forage distribution and yield. Rotational stocking has also been reported to increase carrying capacity and stocking rates (Hull et al., 1967), as well as increase stocker cattle average daily gain (ADG; Walton et al., 1981; Williamson et al., 2016), but this response is not consistent in the literature. On the contrary, Briske et al.…”