Presence of natural radionuclides and toxic elements in monocalcium phosphate, complete feed and pig manure

Naturally occurring radionuclides and toxic elements are ubiquitous in the environment and can pose a great risk to animals' health. Control of these toxic substances in animal diet is essential for animal's welfare, human nutrition risk management as well as environmental protection. Our study addresses these issues by determining a content of natural radionuclides (⁴⁰K, ²³⁸U and ²²⁶Ra), and toxic elements (Cd, Cr, As) in total of 108 samples: 36 monocalcium phosphate, 36 complete feed and 36 pig manure samples that were collected from 6 different commercial farms in the Republic of Serbia. In monocalcium phosphate the content of ⁴⁰K, ²³⁸U and ²²⁶Ra ranged from 7.6-23.4 Bq kg^-1, 13.2-1778 Bq kg^-1 and 3.6-13.5 Bq kg^-1, respectively. In complete feed samples, ⁴⁰K ranged from 170 to 306 Bq kg^-1, ²³⁸U from minimum detectable activity (MDA) to 9.1 Bq kg^-1, and ²²⁶Ra from MDA-5.5 Bq kg^-1, while in pig manure ⁴⁰K ranged from 146 to 531 Bq kg^-1, ²³⁸U from MDA-30.1 Bq kg^-1, and ²²⁶Ra from MDA-10 Bq kg^-1. The concentrations of Cd, Cr and As in monocalcium phosphate were 0.26-14.9 mg kg^-1, 10.3-497 mg kg^-1, and 4.2-5.5 mg kg^-1, respectively. In complete feed, the content of Cd, Cr and As ranged from minimum detectable concentration (MDC) - 0.78 mg kg^-1, 0.30-7.41 mg kg^-1, and 0.09-0.31 mg kg^-1, respectively. In pig manure Cd, Cr and As ranged from 0.8-2.3 mg kg^-1, 2.3-22.2 mg kg^-1, and 0.51-5.45 mg kg^-1, respectively. The obtained results showed that Cd concentration in monocalcium phosphate exceeded the maximum permissible legislative concentrations for phosphate additives. Monocalcium phosphate is the main source of ²³⁸U and Cr in complete feed, while Cd derives from other sources. For that reason excessive use of monocalcium phosphate can lead to high levels of these pollutants in complete feed and consequently in manure.