Document Type : Research Articles
Department of Animal Science, Faculty of Agriculture, Birjand University, Birjand, Iran
Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
Professor, Department of Vetrinary Science, Ferdowsi University, Mashhad, Iran
Introduction Environmental pollution, including pollution caused by urban and industrial sewage, factories and vehicles, causes pollution of natural resources in the environment, including water and fodder. The entry of these elements into the body of animals and their accumulation increases their concentration in products and enters the human food chain. Contamination of milk, meat and other edible tissues of animals with heavy metals is also a worrying issue and threatens food hygiene and human health because these elements are not naturally present in edible tissues and even very small amounts of them can be cause severe side effects. Scientists have mentioned the main cause of contamination of meat and animal tissues is feeding them from contaminated fodder sources or rearing them near contaminated areas. In the studies conducted in different countries, the amounts of heavy elements were more than allowed.
Material and methods In order to investigate the amounts of heavy metals including lead, cadmium, chromium, arsenic and nickel in milk and body tissues of dairy cows in North Khorasan province, two experiments were conducted in three regions and the amounts of heavy metals in milk and body tissues of dairy cows using the device Inductively coupled plasma-atomic diffusion (ICP) was measured, and studied.
In the first experiment, three dairy cattle farms were selected in three regions, two farms were located in two regions at equal distances from large industries, and the third region was selected as a control region far from large industries. In each of the farms, 10 dairy cows (5 first lactation and 5 second lactation and above) was sampled and the amounts of elements were measured. In the second experiment, muscle, heart, liver, kidney and lung tissues were sampled from 5 dairy cows from each regions that were removed and sent to the slaughterhouse for reasons such as mastitis and reproductive problems. Heavy metals, including lead, cadmium, chromium, arsenic and nickel, were measured in the tissues by an inductively coupled atomic diffusion plasma (ICP) device.
Result and discussion The results of the first experiment showed that the amount of arsenic, cadmium and lead in the milk of Holstein cows was not affected by different regions. However, the amount of chromium and nickel in the milk of Holstein cows was significantly affected by different regions. Also, the amount of arsenic, cadmium, nickel and lead in the milk of Holstein cows was not affected by age and the interaction of region and age. But the amount of chromium was affected by age and the interaction of region and age. The amount of arsenic, cadmium and lead metals in the thigh muscle tissue of Holstein cows in different regions was not significantly affected by regions. However, the amount of chromium and nickel in the thigh muscle tissue was significantly affected in different areas. The amount of arsenic, chromium, nickel and lead in the heart tissue was not significant in any of the regions (Shirvan, Esfrayen and Bojnoord). The amount of cadmium in the heart tissue of Holstein cows was significantly affected by different regions. Thus, the highest amount of cadmium in heart tissue was observed in Bojnord region and the lowest in Esfrayen region. The amount of chromium, nickel and lead in the tissue of all Holstein cows in different regions was not affected. However, the amount of arsenic and cadmium in the kidney tissue was significantly affected in different areas (Shirvan, Esfrayen and Bojnoord). Based on the obtained results, there was no significant difference in the amount of arsenic, cadmium and lead in lung tissue in different regions. However, the amount of chromium and nickel in the lung tissue of Holstein cows was significantly affected in different regions. Chromium enters various environmental sources (air, water and soil) from a wide range of natural and human sources, the most of which is emitted from industrial activities. When heavy metals are present in the air, feed and water of animals, they eventually accumulate in their tissues.
Conclusion:Although the amounts of heavy metals in many cases were not significantly different between the investigated areas, but their amounts were higher than the standard values reported for those heavy metals in products such as milk, Regarding the concentration of elements in tissues regardless of their regions and distance, the highest values of elements in tissues were related to the concentration of lead element and the liver had the highest concentration of lead compared to other tissues. so the use of compounds such as absorbents to reduce the concentration of these metals in dairy cattle products can be suggested and considered as a solution.
key words: Body tissues, Dairy cows, Heavy metals