Copper nutrition of goats grazing native and improved pasture with the seasonal variation in a semiarid region of Pakistan

A study was conducted to determine the Cu nutrition status of different classes of grazing goats during two different seasons on a farm located in southern Punjab, Pakistan. A complete free-choice mineral supplement was available to all animals throughout the year. Soil, forage, feed, water, and animal samples (plasma, milk, feces, and urine) were taken eight times during the year (four times in each season). Soil Cu was not affected by seasonal changes and was higher than the requirements of plants during both seasons. Forage Cu level showed significant seasonal fluctuations being higher in winter than in summer forage. In winter, it was adequate for goats but found to be borderline to deficient during summer. Copper contents of feed and water showed no seasonal fluctuation complementing the forage Cu to meet the requirement of animals. For all classes of goats, plasma Cu was higher in winter for the majority of collections. Plasma Cu of non-lactating goats was found to be highest for all classes of goats and was higher (P < 0.05) than the normal range in non-lactating and male goats during both seasons, but in lactating goats, plasma Cu was marginally deficient only during the summer. Fecal and urine Cu concentrations were not affected by seasonal changes but found to be higher in non-lactating goats as compared to lactating animals due to its secretion through milk in lactating animals, which contained the same Cu level during both winter and summer. Based primarily on plasma analyses, it was concluded that Cu was marginally deficient in lactating goats during summer. Copper should be continuously supplemented to grazing animals in this semiarid region of Pakistan. Further research is needed to elucidate interactions among Cu, Mo, and S and direct relationships between Cu and S. © 2005 Elsevier B.V. All rights reserved.