The Effect of Different Physiological Reproduction Conditions on Estradiol (E2) Residues in Local Raw Milk

Abstract

Objective: The aim of this study was to evaluate the estradiol (E2) residues found in milk from local dairy farms of cows in different physiological reproduction states to determine whether the E2 residues were still within normal limits for consumption. Materials and Methods: This research used 22 adult Friesian Holstein Crossbreed (PFH) cows that were divided into 3 groups; A: Productive cows (non-pregnant and non-estrus conditions), B: Pregnant cows in the second trimester of gestation and C: Estrus cows. All of the cows were in the productive age range of 2-4 years old or in the second to fourth parity. Blood and milk samples were collected twice a day. Blood samples were kept at room temperature for 24 h to collect the serum and then stored in a freezer. The milk was centrifuged at 2000 rpm for 10 min and the supernatant was collected and then kept frozen. The estradiol assay was conducted with an ELISA kit from Calbiotech. The body weight was estimated with Rondo measuring tape and the daily milk production was evaluated. The data were analyzed in a completely randomized design with IBM SPSS 23. Results: Reproduction conditions affected the E2 residues in milk (p<0.05). The estradiol residues found in milk were greater than in serum due to an unknown mechanism. The highest E2 residues were observed in the milk of pregnant cows (187.425±27.315 pg mL^–1). Conclusion: It can be concluded that theE2 residues found in milk in every group was very low compared with the normal estradiol levels consumed by humans.