Abstract
Copper (Cu) and zinc (Zn) status of prepartum and postpartum breeding beef cows and newborn calves was investigated by evaluating mineral concentrations in diets and blood plasma of cattle. The investigations were conducted at the Shikoku National Agricultural Experimental Station (Kagawa) and Tsudaka Livestock Farm of Okayama University (Okayama). The cows from Kagawa were set in grazing condition or fed with hay produced in the station during the experimental period. The cows from Okayama were set in grazing condition until 30 days before the expected calving day, and after that, they were housed and supplied with soilage, silage, rice straw and concentrate. The Cu, Molybdenum (Mo) and Zn concentrations in diets from Kagawa and Okayama ranged from 5.67 to 8.60 ppm, from 0.39 to 3.02 ppm and from 24.9 to 54.3 ppm on a dry matter basis, respectively. The iron (Fe) concentration in hay from Kagawa was 245 ppm, on the other hand, the Fe concentration in pasture grass and a diet during the housing period from December to March from Okayama were 401 and 368 ppm, respectively. The plasma Cu concentrations of cows Kagawa ranged from 0.89 to 1.02 μg/ml after calving, whereas the plasma Cu concentrations of cows from Okayama were lower than the critical level (0.65 μg/ml) from 92 days before calving to 30 days after calving. The plasma Cu concentrations of calves from Kagawa and Okayama were 0.33 and 0.30 μg/ml on 1 day after birth and increased to 0.93 and 0.88 μg/ml on 8 days after birth, respectively. The plasma Zn concentrations of cows and calves from Kagawa and Okayama were higher than the critical level (0.6-0.8 μg/ml) with the exception of cows from Kagawa On 1 day after birth. It is suggested that the low plasma Cu concentration of cows from Okayama during pregnancy was likely caused by increased Cu demand of fetus under the condition of excessive Fe concentrations in the diets. Judging from the plasma Zn concentrations, Zn status of cows and calves from Kagawa and Okayama was normal.
