No abstract

Double-cropping systems have been suggested as a way to increase annual dry matter production per hectare, while simultaneously delivering environmental benefi ts. Past research seems to indicate that there is a genotypic eff ect for the suitability of a crop for use within double-cropping systems; however, despite sorghum's [Sorghum bicolor (L.) Moench] diverse genetic background, there has not been a great deal of work done to explore this response for this crop. Twelve sorghum varieties were grown as sole crops and within a double-cropping system with winter triticale [× Triticosecale Wittmack] in central and northern Iowa. Results showed that although the single-cropping system produced slightly higher biomass yields, there were no signifi cant diff erences in total production between the two systems for several of the sorghum varieties. Th ese varieties were characterized as earlier maturing ones that had nearly maximized dry matter production at the time of harvest for the double-cropping system, and thus, any potential loss in sorghum yield was supplemented by the biomass production from the triticale crop. However when the chemical composition of the crops was considered, the theoretical ethanol yield of the single-cropping system was greater than the double-cropping system for all sorghum varieties. Although triticale was capable of off setting any potential loss in dry matter, as an ethanol feedstock it was inferior to sorghum.

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 Apr. 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.

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...

There were several methods that were well suited for predicting the digestible portion of forage materials, with the acid detergent lignin and Klason lignin method giving the highest correlation across the three types of forage. The continued use of Na₂SO₃ during preparation of Van Soest fibres needs to be evaluated owing to its ability to reduce lignin concentrations and effectiveness in predicting the utilisation of feedstuffs and feedstocks. Because there was little correlation between the lignin concentration and the biomass materials, there is a need to examine alternative or develop new methods to estimate lignin concentrations that may be used to predict the availability of carbohydrates for ethanol conversion.