328. Flavonoid Supplementation via Alfalfa Alters Arterial Hemodynamics and Alleviates Fescue Toxicosis in Sheep.

Abstract Consumption of ergot alkaloids in endophyte-infected tall fescue (E+TF) can negatively impact the welfare and performance of ruminant livestock by altering physiology including increasing systemic vasoconstriction, disrupting thermoregulation and consequently susceptibility to thermal stress. Legumes contain flavonoids that are known hypotensive agents and previous experiments have demonstrated that purified flavonoids produced by alfalfa and other legumes can alleviate fescue toxicosis-induced arterial vasoconstriction; however, supplementation with flavonoids via alfalfa forage has not been evaluated. Therefore, the objective of this study was to determine if alfalfa supplementation to provide 0.25 to 0.5 mg kg BW-1 total flavonoids (biochanin A + formononetin + luteolin + apigenin) would alter arterial hemodynamics and mitigate fescue toxicosis in sheep. Nine mature, ruminally cannulated Polypay wethers (88.9 ± 2.3-kg) were randomly assigned to a 3 × 3 crossover design study evaluating the following treatments: distillers dried grains with solubles (DDGS) only control (CON; 1.24 g kg BW-1 DDGS), 0.25 mg kg BW-1 flavonoids (0.25 ALF; 0.62 g kg BW-1 DDGS + 0.64 g kg BW-1 alfalfa), or 0.50 mg kg BW-1 flavonoids (0.50 ALF; 1.29 g kg BW-1 alfalfa). All treatments were made isonitrogenous with DDGS. Wethers were first adapted to the basal diet (85% orchard grass pellets:15% concentrate mix) limit fed daily for 3-wk. The experiment was conducted over three consecutive 7-d periods during which wethers received E+ TF seed (15.0 µg kg BW−1 ergovaline+ergovalanine) and their assigned treatments via the rumen cannula immediately prior to feeding (0800-h) daily. On days 5 through 7 of each 7-d period, carotid artery hemodynamics via color Doppler ultrasonography (0730-h) and thermoregulatory measures (0730-h and 1600-h; respiration rate; rectal and rib temperatures; rib transepidermal water loss [TEWL]) were collected. All data were analyzed by repeated measures using the MIXED procedure of SAS (v. 9.4). Dry matter and water intake were unaffected by treatment (P > 0.1). Carotid artery area was 36% greater and blood flow rate was 80% faster in both alfalfa treatments when compared with the DDGS only CON (P < 0.01). Rib skin temperature and TEWL (1600-h only) were ∼1 ˚C higher and ranged from 44% to 59% greater in both alfalfa treatments than in CON, respectively (P ≤ 0.03). There was a trend for CON rectal temperature to be lower at 1600-h than 0.5 alfalfa treatment (P = 0.10). Overall, CON wethers had higher respiration rates (0730-h: 63 breaths min-1, 1600-h: 135 breaths min-1) than 0.25 to 0.50 ALF wethers (0730-h: 40 breaths min-1, 1600-h: 110 breaths min-1; P < 0.01). In conclusion, supplementation of flavonoids via alfalfa alters arterial hemodynamics and improves thermoregulation in ruminants challenged with fescue toxicosis. Future research is needed to determine the optimal amount of flavonoids via alfalfa required to alleviate fescue toxicosis.