Influence of Ascophyllum nodosum on selenium and antioxidants in beef cattle

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Texas Tech University

Tasco, a proprietary product derived from a brown kelp {Ascophyllum nodosum). has altered antioxidants in plants and animals. Selenium (Se) is a component of glutathione peroxidase, a cellular antioxidant, which is closely related to vitamin E in activity. Antioxidants have been implicated in the improved immune fiinction of steers and shelf life of the meat from steers that grazed pastures treated with Tasco. Therefore, experiments were conducted to determine the effects of Tasco products on Se concentrations in forage and cattle. In Experiment 1. Tasco-Forage (a water-soluble extract) was applied (3.5 kg/ha in April and July) to endophyte Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin) -infected and endophyte-free tall fescue {Festuca arundinacea) grazed by Angus steers in Virginia during 1995 (initial mean BW 245 kg; SD = 20), 1996 (initial mean BW 234 kg; SD = 9), and 1997 (initial mean BW 265 kg; SD = 5). Tasco tended (P = 0.11) to decrease Se in endophyte-infected tall fescue and increased (P < 0.05) Se in endophyte-free tall fescue (interaction; P < 0.05) when averaged over years and dates. By the end of the grazing season, steers that grazed Tasco-treated fescue had higher (P < 0.05) Se in serum (1996) and whole-blood (1997) than steers that grazed non-treated fescue, regardless of the endophyte. Endophyte-infected tall fescue decreased (P < 0.05) serum Se (1996) and whole-blood Se (1997) compared with non-infected fescue. At the end of grazing, steers were finished on a feedlot in Texas. No differences in serum Se were observed following feedlot fmishing. In Experiment 2, Tasco-14 (a meal from dried, ground, intact A. nodosum) was fed (0, 1.5, or 3.0% of diet, DMB) to crossbred steers (Trial 1 initial mean BW = 332 kg, SD = 37; Trial 2 initial mean BW = 340 kg, SD = 18) during a 127-d eedlot finishing period. Steers were fed a diet based on steam-flaked com {Zea mays L.: Trial 1) or steam-flaked milo {Sorghum bicolor; Trial 2). No differences in serum Se were observed by harvest, but liver Se decreased linearly (P < 0.05) at harvest as a result of Tasco treatment in Trial 2. In Experiment 3, Tasco-EX fed to steers for the final 2-wk in the feedlot, at 0, 1, and 2% of the dietary DM had no effect on serum Se but linearly (P < 0.05) decreased serum vitamin A. Serum vitamin E of steers fed 1% Tasco did not increase as much as controls (P < 0.05) over the 2-wk period. Vitamin A, E, and Se were not affected in liver. In Experiment 4, sale bam heifers were supplemented (90 g d"' target consumption) with Tasco-EX in the drinking water for a 2-wk period. No effect on serum Se was observed at the end of the 2-wk supplementation period as a resuh of Tasco treatment. In Experiment 5, Tasco-14 was fed (0.18 kg hd'' d'') to Angus-crossbred (initial mean BW = 238 kg, SD=18) steers for 2-wk before transport to the feedlot, and for 2-wk after arrival. No effect of Tasco treatment on semm Se was observed immediately before or immediately after transport. No effect on whole-blood Se was observed 2-wk after transport. Tasco increased blood Se in grazing steers, but changes in blood Se only partially reflected differences in forage Se. Effects of Tasco on forage Se concentration depended on the presence of the endophyte. Application of Tasco to forage in Se deficient regions might improve Se status of grazing livestock. Presence of the endophyte decreased Se in the animal but not in the forage. Direct feeding of Tasco to steers did not aher serum Se, but decreased liver Se with long-term feeding and depressed serum vitamin A and E with short-term feeding. Treatment of beef heifers with Tasco in the drinking water did not aher serum Se. Tasco increased Se concentrations in endophyte-free tall fescue forage from Se deficient areas, but not endophyte-infected tall fescue. Other mechanisms working through the forage that are not totally understood, as well as ahered Se concentration of the forage, might provide an altemative to direct Se supplementation in deficient areas by increasing the Se status of cattle grazing both endophyte-infected and endophyte-free tall fescue.

Antioxidants, Ascophyllum nodosum, Beef cattle, Selenium in animal nutrition