In the past century, recombinant DNA technology has opened new avenues for modern agriculture with the introduction of genetically modified cereal (GMO) crops. However, contamination with GMO elements remains an open problem in the field of transgenic feed. Therefore, in order to solve this problem, we are investigating and searching the degree of degradability of the residual elements of the foreign DNA-derived cry1Ab gene in blood, milk, urine and feces samples of Holstein cattle suspected to be on GMO diet Bt fed corn to be infected. In our preliminary tests, we randomly collected 30 different samples from different dairy farmers (blood, milk, urine and faeces samples) using routinely available methods and then performed a PCR test using specific primers of the cry1Ab gene sequence in order not to distinguish between transgenic and genetically modified corn and their products. Our results showed evidence for the presence of 206 bp amplicons of the cry1Ab gene derived from stool samples. However, the result provides no contamination by GMO elements in blood, milk or urine samples. Taken together, the present results confirm the applicability of imported Bt corn in formulating diets for dairy farmers. However, it is worth discussing these interesting achievements also on the low contamination rate of GMO maize and its residual elements during the current work. Overall, our method was the one that yielded the most cost-effective test, and more work is certainly needed to decipher these complexities to ensure risk assessment and up-to-date highlights of biosecurity regulations. Manuscript profile