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Sex and the sewage

A new study links sewage sludge, used as pasture fertilizer, to stunted testes in fetal lambs. The finding signals a developmental problem that could have consequences in adult male sheep.

Researchers in Scotland treated lamb pastures for 5 years with either conventional inorganic fertilizers or sewage sludge, the nutrient-rich by-product from sewage-treatment plants. The scientists applied the fertilizers so that they would provide equal amounts of the plant nutrient nitrogen.

In the fifth year, ewes that had grazed on each field for the study's duration were slaughtered three-quarters of the way through their pregnancies. Although all these sheep weighed about the same, the female fetuses from sludge-treated pastures were 12 percent smaller, and their brothers 15 to 36 percent smaller, than fetal lambs from conventionally fertilized sites.

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