Effects of Long-Term Consumption of Sewage Solids on Blood, Milk and Tissue Elemental Composition of Breeding Ewes

Abstract

Fine-wool ewes received for 2 yr a complete pelleted basal diet (11% protein) or the basal diet fortified with 3.5% cottonseed meal (CSM; 12% protein) or gamma-irradiated (1 megarad) dried solids (SS; 12% protein) from primary (undigested) sewage (Las Cruces, New Mexico, municipal sewage). Five ewes fed each diet were sampled to determine Ag, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb and Zn in blood, milk and tissues. Tissues and blood were sampled at slaughter 40 d after weaning of lambs. Mean whole blood mineral concentrations were similar (P less than .05) among treatments 3 d postpartum; however, at 42 d after lambing (mean +/- SE) both basal- (54 +/- 2 micrograms/ml) and sewage-fed (54 +/- 2 micrograms/ml) ewes had elevated (P less than .05) blood Ca compared with ewes fed CSM (46 +/- 2 micrograms/ml). No biologically important differences were detected in the concentrations of elements in milk. Ewes fed SS had lower (P less than .05) blood Fe than animals in the other groups. Sewage-fed ewes also had higher (P less than .05) liver Fe (1,092 +/- 100 micrograms/g) than basal-fed ewes (626 +/- 100 micrograms/g); whereas Fe in CSM-fed ewes (873 +/- 100 micrograms/g) was similar to both. Basal-fed animals had 1.1- to 1.3 times more (P less than .05) liver Mg and two- to threefold higher liver Na than CSM or SS. Livers from SS-fed ewes had higher concentrations (P less than .05) of Cd (1.5- to 1.6-times) and Pb (1.4- to 1.9-times) than livers from CSM- or basal-fed ewes.(ABSTRACT TRUNCATED AT 250 WORDS)