Effect of selenium concentration on feed preferences by cattle and sheep

Authors: Pfister, James; Davis, Thomas - Zane; HALL, JEFFERY - Utah State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2013
Publication Date: 12/1/2013
Publication URL: http://handle.nal.usda.gov/10113/62981
Citation: Pfister, J.A., Davis, T.Z., Hall, J.O. 2013. Effect of selenium concentration on feed preferences by cattle and sheep. Journal of Animal Science. 91(12):5970-5980.

Interpretive Summary: Selenium-containing plants are reputed to be unpalatable to livestock. The objective of this study was to determine if sheep and cattle could discriminate between forages and feeds with different concentrations of Se. In phase I, freshly-harvested forages (intermediate wheatgrass, Thinopyrum intermedium; alfalfa, Medicago sativa; western aster, Symphyotrichum ascendens) with different Se concentrations were offered to cattle and sheep in preference trials. Se concentrations ranged from 0.8 to 50 parts per million (ppm) in grass, 1.4 to 275 ppm in alfalfa, and 4 to 4,455 ppm in aster. The Se concentration had no effect on the initial or subsequent preferences of sheep or cattle for grass or alfalfa. Cattle developed an aversion to aster after consuming 95% of the offered plant material during the first brief exposure, and subsequently refused to eat any aster plants. Sheep consumption of aster was variable, but their preference was not driven by Se concentration. In phase II, cattle and sheep were offered pellets (each at 1.5% of body weight) containing various concentrations of Se, for 8 h each day. The first trial used pellets with 5 concentrations (0, 5, 25, 45, 110 ppm Se); 2 subsequent trials removed the 5 and 25 ppm Se pellets, respectively. In the 5-pellet trial, consumption of the 0 ppm Se pellet by cattle was greater on all days compared to all other Se pellets. Cattle ate more of the 5 ppm pellet than the higher Se pellets on days 3, 4, and 5. Sheep ate greater amounts of the 0, 5, and 110 ppm Se pellets compared to the 25 and 45 ppm Se pellets on day 1, and sheep consumed primarily the 0 and 5 ppm Se pellets thereafter. In the 4-pellet trial, cattle and sheep consumed more of the 0 ppm Se pellet than the 25, 45, and 110 ppm Se pellets. In the 3-pellet trial, cattle consumption of the 0, 45, and 110 ppm Se pellets differed on days 2 and 3. Sheep consumed primarily the 0 and 45 ppm Se pellets during the 3-pellet trial. We conclude that high Se concentrations in fresh forages had no effect on initial consumption by cattle or sheep. After initial exposure, cattle may have generalized an aversion based on shared flavors in the low- and high- Se asters. When given Se pellets, initial responses were variable, but animals adjusted their intake over time to allow for detoxification when over ingesting Se.

Technical Abstract: Selenium-containing plants are reputed to be unpalatable to livestock. The objective of this study was to determine if sheep and cattle could discriminate between forages and feeds with different concentrations of Se. In phase I, freshly-harvested forages (intermediate wheatgrass, Thinopyrum intermedium; alfalfa, Medicago sativa; western aster, Symphyotrichum ascendens) with different Se concentrations were offered to cattle and sheep in preference trials. The Se concentrations ranged from 0.8 to 50 parts per million (ppm) in grass, 1.4 to 275 ppm in alfalfa, and 4 to 4,455 ppm in aster. The Se concentration had no influence (P > 0.05) on the initial or subsequent preferences of sheep or cattle for grass or alfalfa. Cattle developed an aversion to aster after consuming 95% of the offered plant material during the first brief exposure, and subsequently refused to eat any aster plants. Sheep consumption of aster was variable, but their preference was not driven by Se concentration. In phase II, cattle and sheep were offered pellets (each at 1.5% of BW) containing various concentrations of Se, for 8 h each d. The first trial used pellets with 5 concentrations (0, 5, 25, 45, 110 ppm Se); 2 subsequent trials removed the 5 and 25 ppm Se pellets, respectively. In the 5-pellet trial, consumption of the 0 ppm Se pellet by cattle was greater on all days compared to all other Se pellets (P < 0.001). Cattle ate more (P < 0.001) of the 5 ppm pellet than the higher Se pellets on d 3, 4, and 5. Sheep ate greater amounts of the 0, 5, and 110 ppm Se pellets compared to the 25 and 45 ppm Se pellets (P < 0.0001) on d 1, and sheep consumed primarily the 0 and 5 ppm Se pellets thereafter. In the 4-pellet trial, cattle and sheep consumed more (P < 0.0001) of the 0 ppm Se pellet than the 25, 45, and 110 ppm Se pellets. In the 3-pellet trial, cattle consumption of the 0, 45, and 110 ppm Se pellets differed on d 2 and 3 (P < 0.001), except there was no difference (P > 0.95) in cattle consumption of the 0 and 45 ppm Se pellets on d 1. Sheep consumed primarily the 0 and 45 ppm Se pellets. We conclude that high Se concentrations in fresh forages had no effect on initial consumption by cattle or sheep. After initial exposure, cattle may have generalized an aversion based on shared flavors in the low- and high- Se asters. When given Se pellets, initial responses were variable, but animals adjusted their intake over time to allow for detoxification when over ingesting Se.