Availability of barium selenate administered orally to sheep

Abstract

AVAILABILITY OF BARIUM SELENATE ADMINISTERED ORALLY TO SHEEP J.A. ARCHERA and G.J. .JUDSON B ADcpt of Animal Science, Waite Agricultural Research Institute. Glen Osmond, S.A. 5064 BCcntral Veterinary Laboratories. Dept of Primary Industries, GPO Box 1671, Adelaide. S.A. 5001 An alternative method for providin, selenium to livestock is a subcutaneous injection of barium 0 selenate suspended in a viscous excipient. This method has been shown to be safe for the supplemented animals (Cawley and McPhee 1984) and lon, o-acting (Judson et al. 1991). Deposits of barium selenate persist at the site of injection for at least 56 and 1 19 days in sheep and cattle respectively (Mallinson et al. 1985; Archer and Judson 1994) and may be dangerous to human health if consumed. It has been suggested that the low solubility of barium selenate would mean that it would not be absorbed from the digestive tract (Cooper 1987; Judson et al. 199 1) and hence would present no danger to human consumers. However, barium selenate is soluble in hydrochloric acid (Anonymous 1976) and so may be solublised in the stomach. The purpose of this experiment was to determine whether barium selenate is available when given orally to sheep. Eight 1 year old sheep were given were nil, 100 or 250 mg of barium selenate orally. After 27 days the sheep were slaughtered and samples of blood, liver, kidney cortex and medulla, cardiac and skeletal muscle were collected for selenium assay as described by Archer and Judson (1994). The effect of treatment on selenium concentration in tissues was tested by analysis of variance. Results are presented in Table 1. Table 1. Concentration of selenium bmolkg dry matter) in tissues of sheep 27 days after nil (3 sheep), 100 mg (2 sheep) or 250 mg (2 sheep) of barium selenate was given orally The marked increase in selenium concentration of tissues indicates that the barium selenate was absorbed from the intestinal tract. This availability of selenium from barium selenate is of concern as it suggests that residues of the supplement in meat ingested by humans may be a significant source of selenium. ANONYMOUS (1976). III 'The Merck Index: An Encyclopaedia of Chemicals and Drugs', 9th ed., (Eds M. Windholz, S. Budavari, L.Y. Stroumtsos and MN. Fertig) p. 130 (Merck and Co., Inc.: Rahway). ARCHER. J.A. and JUDSON, G.J. ( 1994). Amt. J. EXP. Agr-ic. (in press). CAWLEY. G.D. and McPHEE, I. (19S4). Vet. Rec. 113: X55-66. COOPER, B.S. (1987). U niversity of Sydney Post-Graduate Committee in Veterinary Science Proceedings 103: 175S6. JUDSON. G.J.. ELLIS, N.J.S., KEMP, B.R. and SHALLOW, M. (1991). ALrst. Vet. .J. 68: X3-j. MALLINSON, C.D., ALLEN, W.M. and SANSOM, B.I. (19S5). Vet. RCC 117: 405-7. 441