Effect of Se on selenoprotein activity and thyroid hormone metabolism in beef and dairy cows and calves J. E. Rowntree 1 , G. M. Hill 2 , D. R. Hawkins, J. E. Link, M. J. Rincker, G. W. Bednar, and R. A. Kreft, Jr. Department of Animal Science, Michigan State University, East Lansing 48824 ABSTRACT: Although Se is essential for antioxidant and thyroid hormone function, factors inﬂuencing its requirement are not well understood. A survey and two experiments were conducted to determine the inﬂuence of cattle breed and age on selenoprotein activity and the effect of maternal Se supplementation on cow and calf selenoprotein activity and neonatal thyroid hor- mone production. In our survey, four cowherds of differ- ent ages representing three breeds were bled to deter- mine the inﬂuence of breed and age on erythrocyte glu- tathione peroxidase activity (RBC GPX-1). All females were nonlactating, pregnant, and consumed total mixed diets (Holstein) or grazed pasture (Angus and Here- ford). In our survey of beef breeds, yearlings had greater average RBC GPX-1 activity than mature cows. In Exp. 1, neonatal Holstein heifers (n = 8) were bled daily from 0 to 6 d of age to determine thyroid hormone proﬁle. An injection of Se and vitamin E (BO-SE) was given after the initial bleeding. Thyroxine (T 4 ) and triiodothy- ronine (T 3 ) concentrations were greatest on d 0 and decreased (P < 0.05) continuously until d 5 postpartum (156.13 to 65.88 and 6.69 to 1.95 nmol/L, d 0 to 5 for T 4 and T 3 , respectively). Reverse T 3 concentrations were Key Words: Cows, Glutathione Peroxidase, Selenium, Thyroid Hormones 2004 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2004. 82:2995–3005 Introduction Selenium is an essential trace mineral for antioxi- dant and thyroid hormone function. Erythrocyte gluta- thione peroxidase (RBC GPX-1; EC 1.11.1.9) and plasma glutathione peroxidase (P GPX-3; EC 1.11.1.9) both require Se (Rotruck et al., 1973; Martin-Alonso et al., 1993) and reﬂect long- and short-term Se status, respectively (Cohen et al., 1985). Thyroxine (T 4 ) is deio- 1 Current address: 107 J. B. Francioni Hall, Louisiana State Univ., Baton Rouge 70803. 2 Correspondence: 2209 Anthony Hall (phone: 517-355-9676; fax: 517-432-0190; e-mail: hillgre@msu.edu). Received December 11, 2003. Accepted June 22, 2004. 2995 3.1 nmol/L on d 0 and decreased (P < 0.05) to 0.52 nmol/ L by d 5. In Exp. 2, multiparous Hereford cows were drenched weekly with either a placebo containing 10 mL of double-deionized H 2 O (n = 14) or 20 mg of Se as sodium selenite (n = 13). After 2 mo of treatment, Se- drenched cows had greater (P < 0.01) plasma concentra- tions than control cows (84.92 vs. 67.08 ng/mL), and at parturition, they had plasma Se concentrations twofold greater than (P < 0.05) control cows (95.51 vs. 47.14 ng Se/mL). After 4 mo, cows receiving Se had greater (P < 0.05) RBC GPX-1 activity than controls; this trend continued until parturition. Colostrum Se concentra- tion was twofold greater (P < 0.05) in Se-drenched cows than control cows (169.97 vs. 87.00 ng/mL). Calves born to cows drenched with Se had greater (P < 0.05) plasma Se concentration, RBC GPX-1, and plasma glutathione peroxidase activity on d 0 compared with calves born to control cows. By d 7, no differences in plasma gluta- thione peroxidase activity in calves were observed. Ma- ternal Se supplementation did not inﬂuence calf thyroid hormone concentrations. Selenium provided by salt and forages is not adequate for cattle in Se-deﬁcient states. dinated to the more metabolically active triiodothyro- nine (T 3 ) by the Se requiring enzyme type 1 deiodinase (EC 3.8.1.4; Beckett et al., 1987). Michigan forages are Se-deﬁcient, containing 0.1 to 0.2 ppm Se (Kubota et al., 1967; Mortimer et al., 1999). Cow Se status can be further reduced as Se is trans- ferred across the placenta during late pregnancy and during early lactation in colostrum. Consequently, calves born from Se-deﬁcient or marginally deﬁcient dams may have compromised Se status. Schrama et al. (1993) reported that neonatal calves are susceptible to cold stress at temperatures below 14.6°C. Approximately 70% of Michigan calves are born between January and April, when temperatures range from -6.7 to 7.8°C (Ritchie, 1991). Therefore, calves must make thermogenic responses to cold. A major form