Toxicity studies on bone tissue from sheep grazing on a pasture treated with sewage sludge
Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
In this study, femur bones and serum from rams and ewes (Ovis aries) bred on pastures fertilized twice annually with sewage sludge (2.25 tonnes dry matter/ha) or on control pastures were analysed. The control pastures was treated with conventional inorganic fertilizer. Both rams and ewes were exposed during development in utero, from conception, and after birth, during lactation, to weaning at 4 months of age. After that the rams were moved to pastures not fertilized with sewage sludge. The ewes, however, were retained on pastures treated with sewage sludge. The animals were slaughtered at 18 months of age and the femur bone was dissected. The peripheral Quantitative Computed Tomography (pQCT) and three-point bending test analyses of the femur bone were evaluated. In rams, the total bone mineral density (BMD) at the metaphyseal part of femur was significantly greater (10.5 %, p<0.05) in treated than control animals. Treated animals also exhibited a reduction in the total cross sectional area (CSA, 11.5 %, p<0.05), the trabecular CSA (17.1 %, p<0.05) and the periosteal circumference (5.7 %, p<0.05). Analysis of the mid-diaphyseal part revealed multiple effects e.g. the total BMD (13.8 %, p<0.05) increased significantly whereas the total CSA (12.1 %, p<0.05) and the marrow cavity (25.8 %, p<0.05) were significantly reduced in the treated rams. The threepoint bending test of the ram femur at the mid-diaphyseal part revealed an increased stiffness (6.4 %, p<0.05) in treated animals. In ewes, the trabecular bone mineral content (BMC) at the metaphyseal part of femur was significantly increased (41.6 %, p<0.05) in the treated ewes. pQCT analysis of the mid-diaphyseal part showed no adverse effects in the treated ewes. Femurs from treated ewes showed a reduction in the load at failure (17.3 %, p<0.05) and stiffness (10.7 %, p<0.05). The serum levels of the bone formation marker BAP, the bone resorption marker CTX and the vitamin D marker 25-OH D did not differ between exposed and control animals, neither for rams nor for ewes. In conclusion, this study shows that exposure to sewage sludge disrupt bone tissue homeostasis in sheep. As the rams were only exposed via placental transfer and mother’s milk, the obtained effects; increased cortical thickness, decreased circumference and decreased marrow cavity must be considered as developmental effects. The increase in femoral trabecular BMC in the ewes is thought likely to be attributable to estrogenic influences in the sludge.
Place, publisher, year, edition, pages
2008. , 30 p.
IdentifiersURN: urn:nbn:se:uu:diva-171012OAI: oai:DiVA.org:uu-171012DiVA: diva2:510044
Subject / course
Master Programme in Biology
UppsokLife Earth Science
Örberg, JanLind, Monica