R. Naresh

Blood lead levels in lactating cows reared around polluted localities; transfer of lead into milk

Lead is pervasive environmental pollutant with potential public health hazard as a contaminant of food from animal origin. The present study examines the blood and milk lead level in animals reared in areas around different industrial activities and to find out correlation between blood and milk lead levels in lactating cows. Blood and milk samples (n = 149) were collected from animals reared around steel processing unit (n = 22), lead-zinc smelter (n = 21), aluminum processing plant (n = 25), rock phosphate mining area cum phosphate fertilizer plant (n = 21), coal mining areas (n = 46) and closed lead but functional zinc smelter (n = 14). Samples were also collected from randomly chosen 52 lactating cows reared in non-polluted areas to serve as controls. Significantly (P < 0.05) higher blood lead level was recorded in animals reared around lead-zinc smelting factories followed by closed lead but functional zinc smelter, aluminum processing unit and steel manufacturing plant, as compared to values recorded for control animals. The highest milk lead level (0.84 +/- 0.11 microg/ ml) was detected in animals reared in the vicinity of lead-zinc smelting unit followed by aluminum processing plant and steel processing unit. Analysis of correlation between blood lead levels and lead excretion in milk through sorting the blood lead values into 9 different ranges irrespective of site of collection of samples (n = 201) revealed significant correlation (r = 0.469 at P < 0.01) between blood and milk lead concentrations. The lactating cows with blood lead levels above 0.20 microg/ml (groups 5-9) had significantly (P < 0.05) higher milk lead excretion than those with blood lead levels from non detectable to 0.20 microg/ml (groups 1-4). Pearson correlation analysis between blood and milk lead concentrations in 122 animals with blood lead <0.20 microg/ml showed non-significant correlation (r = 0.030 at P < 0.05) but a significant correlation was observed between these two parameters with blood lead level above >0.02 microg/ml indicating that the excretion of lead through milk increases with the increased in blood lead level above 0.20 microg/ml.

Milk trace elements in lactating cows environmentally exposed to higher level of lead and cadmium around different industrial units.

The present investigation was carried out to assess the trace mineral profile of milk from lactating cows reared around different industrial units and to examine the effect of blood and milk concentration of lead and cadmium on copper, cobalt, zinc and iron levels in milk. Respective blood and milk samples were collected from a total of 201 apparently healthy lactating cows above 3 years of age including 52 cows reared in areas supposed to be free from pollution. The highest milk lead (0.85+/-0.11 microg/ml) and cadmium (0.23+/-0.02 microg/ml) levels were recorded in lactating cows reared around lead-zinc smelter and steel manufacturing plant, respectively. Significantly (P<0.05) higher concentration of milk copper, cobalt, zinc and iron compared to control animals was recorded in cows around closed lead cum operational zinc smelter. Analysis of correlation between lead and other trace elements in milk from lactating cows with the blood lead level>0.20 microg/ml (n=79) revealed a significant negative correlations between milk iron and milk lead (r=-0.273, P=0.015). However, such trend was not recorded with blood lead level<0.20 microg/ml (n=122). The milk cobalt concentration was significantly correlated (r=0.365, P<0.001) with cadmium level in milk and the highest milk cadmium (>0.10 to 0.39 microg/ml) group had significantly (P<0.05) increased milk cobalt. It is concluded that increased blood and milk lead or cadmium level as a result of natural exposure of lactating cows to these environmental toxicants significantly influences trace minerals composition of milk and such alterations affect the milk quality and nutritional values.

Enhanced Erythrocytic Lipid Peroxides and Reduced Plasma Ascorbic Acid, and Alteration in Blood Trace Elements Level in Dairy Cows with Mastitis

Oxidative stress has been associated in several inflammatory conditions and incriminated in the pathogenesis of many diseases. However, little information is available on the status of plasma antioxidant levels, essential components of important antioxidant enzymes such as copper, zinc and selenium in blood, and the end product of oxidative damage to the erythrocytic polyunsaturated fatty acids in inflammatory udder conditions. Blood samples were collected from three groups of dairy cows, with 21 in each group: animals with healthy udder, clinical mastitis, and subclinical mastitis. These animals were randomly selected from a herd on the basis of the California mastitis test, somatic cell count and total bacterial count. The mean plasma ascorbic acid concentration was significantly lower in cows with subclinical (p = 0.004) and clinical mastitis (p = 0.000) and the erythrocytic lipid peroxide levels were significantly (p = 0.000) higher in clinical mastitis as compared to controls. There was a significant decrease in mean blood zinc concentration in subclinical (p = 0.005) and clinical mastitis (p = 0.000), but an increase in mean blood copper level in the clinical mastitis group. It was concluded that the blood antioxidant status declines in inflammatory udder conditions, suggesting that incorporation of antioxidants may help in better management of mastitis in dairy cows.

Erythrocyte lipid peroxides and blood zinc and copper concentrations in acute undifferentiated diarrhoea in calves.

Undifferentiated acute calf diarrhoea is a major concern for the dairy industry and its aetiopathogenesis remains diverse. The present study aimed to examine the role of oxidative stress through estimation of erythrocyte lipid peroxide levels and blood zinc and copper concentrations using natural cases of diarrhoea in calves aged 15–30 days old. The calves were kept under identical managemental conditions and were provided with pooled whole colostrum during the first three days and thereafter with only whole milk until they were 1 month old. Diarrhoeic (n = 11) and normal calves (n = 11) of the same age group (15–30 days old) were randomly selected from an organized dairy farm for the study. The mean blood zinc concentration (50.01±2.45 μmol/L vs 66.06±3.06 μmol/L) was significantly (p < 0.05) lower and copper concentration was significantly (p < 0.05) higher in diarrhoeic calves (12.90±0.31 μmol/L vs. 9.44±0.16 μmol/L) than in the healthy calves. The erythrocyte lipid peroxides level was higher (p < 0.05) in diarrhoeic calves (6.88±0.23 nmol malondialdehyde (MDA) per mg of haemoglobin (Hb)) than healthy calves (6.27±0.07 nmol MDA per mg Hb). From the results of the study it is concluded that oxidative stress and antioxidant minerals (zinc and copper) might play important roles in the aetiopathogenesis of bovine calf diarrhoea.