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Ergot alkaloids produced by the endophyte [Neofyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon, and Hanlin] of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] are a common problem faced by livestock producers. These toxins are concentrated within seedheads of tall fescue, which cattle were observed to selectively graze. There appears to be little research showing the extent to which alkaloids are released from developing seedheads during digestion. Therefore, the objectives of this study were to determine the amount at which tall fescue seedheads were removed by cattle and to estimate the amount of ergovaline that is released from these tissues. Seedheads from tall fescue pastures were monitored for consumption by steers during summer 2010. Samples were digested with a two-stage procedure, and ergovaline concentrations were determined using high-performance liquid chromatography. By mean stage count 3.91 (Day of Year 155), 60.7 ± 2.87% of seedheads within the pastures had been grazed, and 2 wk later increased to nearly 78.8 ± 0.82%. Ergovaline concentrations of seedheads increased throughout the season and were highest in mid-June. The percentage of ergovaline released from seedheads collected in mid-June was lower than earlier dates, but the difference was small. Results of this study indicate that high concentrations of ergovaline are released from tall fescue seedheads during the growing season, and management strategies should be aimed at controlling reproductive growth of the grass. [ABSTRACT FROM AUTHOR]

Chaparral herbicide has been shown to suppress seedhead emergence in tall fescue [Lolium arundinaceum (Schreb.) Darbysh] and potentially mitigate the effects of fescue toxicosis. A two-year grazing experiment evaluated steers grazed on endophyte- infected fescue-Kentucky bluegrass (Poa pratensis L.) pastures either treated or untreated with Chaparral herbicide to determine if seedhead suppression alleviates fescue toxicosis and increases average daily gain (ADG). Treatments were assigned to six, 3.0-ha fescue-bluegrass pastures in a randomized complete block design with three replications. Pastures were grazed with 48 steers (2.7 steers ha-1) from 9 A pr. to 1 July 2009 and 6 Apr. to 7 July 2010. Reproductive tiller densities in treated pastures were low in both years (<7 m-2) in comparison with untreated pastures (113 and 69 tillers m-2 in 2009 and 2010, respectively). Ergovaline and ergovalinine concentrations were three- to sixfold greater in seeds than in leaf blades and sheaths of vegetative and reproductive tillers. Crude protein, water soluble carbohydrates, and in vitro digestible dry matter concentrations of tillers declined over time at a greater rate in untreated than in treated pastures. Steers on treated pastures had greater (P < 0.01) ADG, lower (P < 0.10) rectal temperatures, and greater (P < 0.01) serum prolactin concentrations. Results indicated that Chaparral herbicide can suppress reproductive development of fescue to increase ADG and reduce the severity of toxicosis. [ABSTRACT FROM AUTHOR]

Nitrogen fertilizer use is generally restricted in bermudagrass [Cynodon dactylon (L.) Pers.]-white clover (Trifolium repens L.) forage systems because it stimulates grass growth and increases competition with the clover, compromising forage nutritive value and prospective forage accumulation. Enhanced efficiency fertilizer nitrogen (N) products hold potential to improve white clover persistence in bermudagrass- clover pastures while providing supplemental N required by the grass. This study evaluated the effect of different enhanced efficiency N formulations (Environmentally Smart Nitrogen [ESN]; methylene urea; SuperU; and 75% ESN, 25% urea blend) and untreated urea on forage accumulation, nutritive value, and legume persistence in a 'Wrangler' bermudagrass and 'Durana' white clover mixture. Nitrogen was applied at four rates (0, 112, 224, and 448 kg N ha-1) in two equal applications each year. By the second year, white clover stands were lesser at the greatest N rates. All enhanced efficiency N sources maintained white clover similar to the unfertilized grass-clover control, but only ESN improved white clover persistence over urea. Total season forage accumulation increased linearly with increasing N rates within all three growing seasons, but dry weather conditions in the last 2 yr resulted in less forage accumulation. Nutritive value decreased with maturity throughout the growing season, but ESN maintained clover in the pasture resulted in overall less fiber components and greater digestibility. Although there was no effect of N source on forage accumulation, the ability of ESN to maintain clover could make it a viable option for fertilization in bermudagrass-white clover mixtures. [ABSTRACT FROM AUTHOR]

Red clover (Trifolium pratense L.) is an important forage legume in the United States. Improving forage quality and biomass yield is an important goal of forage breeding programs. Plant development, particularly the transition from vegetative to reproductive growth, is an important factor affecting biomass accumulation and forage quality. Thus, genetic manipulation of genes that regulate the transition from the vegetative to reproductive phase can be an efficient strategy for genetic improvement of red clover. One such gene is miR156, a microRNA gene that serves as a master regulator of vegetative phase change in land plants. We report here the development of transgenic red clover plants overexpressing the maize Corngrass1 gene encoding two tandem miR156s. The transgenic plants displayed striking phenotypic changes compared with the wild-type plants, including the increased number of shoots, delayed flowering, enhanced forage yield, and improved forage quality. These results suggest that manipulating miR156 or its target genes is a potential tool for genetic improvement of forage legumes. [ABSTRACT FROM AUTHOR]

Previous research has indicated that serotonergic and α-adrenergic receptors in peripheral vasculature are affected by exposure of cattle grazing toxic endophyte-infected (E+; Epichlöe coenophialia) tall fescue (Lolium arundinaceum). The objective of this experiment was to determine the period of time necessary for the vascular effects of ergot alkaloids to subside. Two experiments were conducted to investigate changes in vascular contractile response and vasoconstriction over time relative to removal from an ergot alkaloid-containing E+ tall fescue pasture. In Experiment 1, lateral saphenous vein biopsies were conducted on 21 predominantly Angus steers (357 ± 3 kg body weight) at 0 (n = 6), 7 (n = 6), 14 (n = 5), or 28 days (n = 4) after removal from grazing pasture (3.0 ha; endpoint ergovaline + ergovalinine = 1.35 mg/kg DM) for 126 days. In Experiment 2, lateral saphenous veins were biopsied from 24 Angus-cross steers (361 ± 4 kg body weight) at 0, 21, 42, and 63 days (n = 6 per time point) following removal from grazing tall fescue pastures (3.0 ha; first 88 days endpoint ergovaline + ergovalinine = 0.15 mg/kg DM; last 18 days endpoint ergovaline + ergovalinine = 0.57 mg/kg DM) for 106 total days. Six steers (370 ± 18 kg body weight) off of bermudagrass pasture for the same time interval were also biopsied on Day 0 and Day 63 (n = 3 per time point). Additionally, in Experiment 2, cross-sectional ultrasound scans of caudal artery at the fourth coccygeal vertebra were taken on Days 0, 8, 15, 21, 29, 36, 42, and 45 to determine mean artery luminal area to evaluate vasoconstriction. In both experiments, steers were removed from pasture and housed in a dry lot and fed a corn silage diet for the duration of biopsies and ultrasound scans. Biopsied vessels used to evaluate vasoactivity were cleaned, incubated in a multimyograph, and exposed to increasing concentrations of 4-Bromo-3,6-dimethoxybenzocyclobuten-1-yl) methylamine hydrobromide (TCB2; 5HT2A agonist), guanfacine (GF; α2A-adrenergic agonist), and (R)-(+)-m-nitrobiphenyline oxalate (NBP; α2C-adrenergic agonist) in both experiments and ergovaline (ERV) and ergotamine (ERT) in Experiments 1 and 2, respectively. In Experiment 1, days off pasture × agonist concentration was not significant (p > 0.1) for all four compounds tested. In Experiment 2, GF, NBP, TCB2 and ERT were significant for days off pasture × agonist concentration interaction (p < 0.02) and vasoactivity increased over time. Vasoactivity to agonists was reduced (p < 0.05) when steers were initially removed from E+ tall fescue pasture compared to bermudagrass, but did not differ by Day 63 for any variable. Luminal areas of caudal arteries in steers grazed on E+ tall fescue relaxed and were similar to steers that had grazed bermudagrass for 36 days on non-toxic diet (p = 0.15). These data demonstrate changes in peripheral vasoactivity and recovery from vasoconstriction occur beyond five weeks off toxic pasture and 5HT2A receptors appear to be more dramatically affected in the lateral saphenous vein by grazing E+ tall fescue pasture than adrenergic receptors. [ABSTRACT FROM AUTHOR]