| Abstract |
This study investigated whether heavy metals present in pasture soils are absorbed by grazing ewes, transferred through their milk to lambs, and how this affects milk production and lamb growth performance. One hundred lactating ewes were divided into two groups of fifty and grazed on two pastures, Oulands (VPA1) and Kikuyu (VPK1), maintained under similar management and environmental conditions. Soil and leaf samples from both pastures were analysed to determine heavy metal concentrations, while lambs were weighed at birth and at weaning to assess growth and productivity.
Results showed that the VPA1 pasture contained significantly higher levels of heavy metals than VPK1. Ewes grazing on VPA1 exhibited reduced udder development, lower milk yields, and overall poorer health compared with those on VPK1. Consequently, lambs nursing from these ewes displayed slower growth rates and significantly lower weaning weights. In contrast, ewes grazing on the less-contaminated VPK1 pasture maintained healthy milk production, resulting in improved lamb performance.
The findings confirm that elevated heavy metal concentrations in grazing soils can be transferred through the food chain, affecting both ewe productivity and lamb development. As sheep may ingest 10–30% of their daily dry matter intake from soil, their exposure risk is considerable. The study concludes that bioaccumulation of heavy metals adversely impacts livestock health and production efficiency. Therefore, effective soil management and continuous monitoring of heavy metal contamination are essential to safeguard animal welfare, optimise growth performance, and ensure the safety of meat and dairy products for human consumption.
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