Location: Rangeland and Pasture Research
Title: Effects of supplementary selenium source on the blood parameters in beef cows and their nursing calves Authors
|Beck, Paul -|
|Hallford, Dennis -|
Submitted to: Biological Trace Element Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2013
Publication Date: April 15, 2013
Citation: Gunter, S.A., Beck, P.A., Hallford, D.M. 2013. Effects of supplementary selenium source on the blood parameters in beef cows and their nursing calves. Biological Trace Element Research. 152(2):204-211. Interpretive Summary: Selenium is one of the most common nutritional deficiencies that cattle producers must manage when cattle grazing on the Coastal Plain. Selenium is an important mineral assisting with enzyme function in the blood which is part of the anti-oxidative system that protects the animal’s health. The most commonly used selenium supplement today is sodium selenite; it is inexpensive and easily available. A newer form of organic selenium is seleno-yeast. Research in pigs has shown it to be eight time more available than sodium selenite. To assess the value of this novel selenium source, beef cows nursing calves were supplemented with these commercially available sources. The selenium sources and levels fed tested were within Federal Drug Administration limits and were compared to no selenium supplementation. Whole blood concentrations of selenium and glutathione peroxidase activity, an enzyme, are the two most widely used assessment tools for measuring selenium status. Both selenium sources increased the whole blood concentrations and the glutathione peroxidase activity in the cows, but seleno-yeast was more effective than sodium selenite. Calves primarily receive their dietary selenium through the milk and calves nursing selenium supplemented cows showed acceptable whole blood concentrations and the glutathione peroxidase activities at birth. However, after three months the calves nursing calves supplemented with sodium selenite began to show signs of a potential selenium deficiency. On the other hand, calves nursing cows supplemented with seleno-yeast still had more than adequate whole blood concentrations and the glutathione peroxidase activity. The difference between these two selenium supplements probably results from the fact that the selenium concentration in milk from cows supplemented seleno-yeast is three time higher than from cows supplemented with sodium selenite. Hormones monitored in this research are regulators of growth and metabolism, yet selenium supplementation had no effect thyroid hormones or insulin-like growth factor 1 concentrations. Selenium supplementation of pregnant beef cows benefited cows by increasing whole blood selenium and glutathione peroxidase activities with either source. However, the use of seleno yeast as a selenium supplement to lactating cows increased the whole blood selenium and glutathione peroxidase activities in thier nursing calves, yet had no effect on hormones that regulate growth and metabolism.
Technical Abstract: Over 2 years, 32 beef cows nursing calves were randomly selected from a herd of 120 that were managed in 6 groups and were assigned to six 5.1-ha bermudagrass (Cynodon dactylon [L.] Pers.) pastures. Treatments were assigned to pastures (2 pastures/treatment) and cows had ad libitum access to 1 of 3 free-choice minerals: 1) no supplemental selenium (Se), 2) 26 mg of supplemental Se from sodium selenite/kg, and 3) 26 mg of supplemental Se from seleno yeast/kg (designed mineral intake = 113 g/cow daily). Data were analyzed using a mixed model; year and pasture were the random effects and treatment was the fixed effect. At the beginning of the calving and breeding seasons, cows supplemented with Se had greater (P < 0.01) whole blood Se concentrations (WBSe) and glutathione peroxidase activities (GSH-Px) than cows receiving no supplemental Se; cows fed seleno-yeast had greater (P </= 0.05) WBSe than cows fed sodium selenite, but GSH Px did not differ (P >/= 0.25) between the two sources. At birth and near peak lactation (late May), calves from cows supplemented with Se had greater (P < 0.01) WBSe than calves from cows fed no Se and calves from cows fed seleno-yeast had greater (P </= 0.01) WBSe and GSH-Px than calves from cows fed sodium selenite. Thyroxine (T4), triiodothyronine (T3), and the T4:T3 ratio in calves did not differ among treatments (P >/= 0.35). At birth, IGF-1 was greater (P = 0.02) in calves nursing cows with no supplemental Se than in ones with supplemental Se; in calves nursing cows with supplemental sodium selenite, IGF-1 did not differ (P = 0.96) from ones offered supplemental seleno-yeast. Selenium supplementation of gestating beef cows benefited cows and calves by increasing WBSe and GSH Px. The use of seleno yeast as a Se supplement compared to sodium selenite increased the WBSe and GSH-Px of both cows and their calves, yet had no effect on T4 conversion or IGF-1 concentrations.