Bovine milk chain in Italian farms. II. Boron levels in soil, gravitational and clean water, bovine diet, and milk

摘要

The objectives of this study were to evaluate the distribution and fate of boron in agricultural environment, by determining the levels of boron in soil, beverage, irrigated water and silage of dairy cattle, as well as in milk, and to evaluate the boron biotransfer factor to milk, considering the bovine milk chain. Between 2003 and 2004, soil, crops, beverage and irrigated water samples were collected along with milk from lactating dairy cows from Italian dairy farms at the national (60 farms) and regional (10 farms) levels. At the national level, the average boron content in drinking water was 117 micro g/litre which was way below the allowable limit of the European and Italian law at 1000 micro g/litre. In milk samples, the total boron content ranged from 108 to 574 micro g/litre, while in feed and silage samples, boron levels ranged from 5.06 to 65.9 and 2.64 to 38.8 mg/kg. At the regional level, the average boron contents in drinking (111.34 micro g/litre) and irrigated water (109.6 micro g/litre) were lower than the legal limits for drinking water. In milk, boron levels ranged from 95 to 468 micro g/litre, while in feed and silage samples, the values were similar to the national level. The boron level in soils was within the normal limits and ranged from 16.85 to 87.06 mg/kg. The cow's biotransfer factors (BTFs, day/litre) for boron in milk at the national level were up to 14.31x10-4 and 24.49x10-4 (Cuneo province, for feed and silage, respectively), related to the large water intake of lactating cows. At the regional level, boron levels in feed and silage were 8.73x10-4 and 7.92x10-4. Because boron is not magnified in the food chain and its relatively rapid excretion in the urine, the boron levels in Italian dairy farms do not constitute a problem.