Determination of copper status of grazing sheep: seasonal influence

A study was conducted to determine the copper status of different classes of grazing sheep during two different seasons on a farm located in southern Punjab, Pakistan. A complete free-choice supplement was available to all animals throughout the year. Soil, forage and blood plasma from animals were taken eight times during the year (2005) (four times in both summer and winter seasons). Soil Cu2+ was affected by the seasonal changes (P<0.001), higher in summer than that in winter and was significantly higher than the need of plants during both seasons. While forage Cu2+ level showed non-significant seasonal (P>0.05) fluctuation in winter. It was adequate for ruminants’ requirements during both seasons. plasma Cu2+ concentrations of all classes of sheep were significantly higher in winter than that in summer showing the seasonal changes (P<0.001). Higher plasma Cu2+ was found in male sheep than lactating and non-lactating sheep during both seasons. The low Cu2+ in plasma in lactating sheep may have been due to its secretion in milk. In winter forage Cu2+ contributed in enhancing the plasma Cu2+ levels, but in summer the forage Cu2+ level, although very high, was ineffective in elevating plasma Cu2+ levels in all classes of sheep. Based primarily on plasma analyses it was concluded that although, the adequate level of plasma Cu2+ was found, it was on borderline deficient levels. Thus supplementation is needed with mixture containing Cu2+. The plus copper should be continuously supplemented to grazing animals in this semiarid region of Pakistan.