Quantification of Prednisolone Residues in the Milk of Mastitic Dairy Cows in Tehran Province, Iran, Using Liquid Chromatography-Mass Spectrometry (LC/MS)

Mojtabavi, Sara; Motallebi, Abbasali; Akbari, Ghasem

doi:10.22034/jfss.2026.598264.1017

Quantification of Prednisolone Residues in the Milk of Mastitic Dairy Cows in Tehran Province, Iran, Using Liquid Chromatography-Mass Spectrometry (LC/MS)

Articles in Press

Document Type : Original Article

Authors

Sara Mojtabavi ¹

Abbasali Motallebi ²

Ghasem Akbari ³

¹ Department of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran

² Department of Hygiene, Science and Research Branch, Islamic Azad University, Tehran, Iran

³ Department of Food Hygiene and Quality Control, Science and Research Branch, Islamic Azad University, Tehran, Iran

10.22034/jfss.2026.598264.1017

Abstract

Bovine mastitis, a prevalent inflammatory condition in dairy cows, is commonly treated with corticosteroids such as prednisolone, raising concerns about veterinary drug residues in milk and food safety. This study quantified prednisolone residues in milk from mastitic dairy cows in Tehran province, Iran, using Liquid Chromatography-Mass Spectrometry (LC/MS). Thirty lactating cows with clinical mastitis were randomly assigned to five treatment-duration groups (n=6 each) and received a commercial intramammary formulation containing 5 mg prednisolone per dose once daily for one to five consecutive days. Milk samples were collected 12 hours after the final treatment, and one pooled milk sample was analyzed separately. Prednisolone concentrations increased with increasing treatment duration, from 24.3 ± 4.6 ng/mL (day 1) to 170.0 ± 11.4 ng/mL (day 5). The single pooled sample contained 27.0 ng/mL prednisolone. The concentrations measured in the five treatment groups exceeded the European Union maximum residue limit (MRL) of 6 µg/kg (approximately 6 ng/mL), by approximately 4- to 28-fold. These findings indicate that milk collected 12 hours after the final treatment exceeded the applicable residue limit under the conditions tested. The study does not establish a withdrawal period; serial post-treatment sampling would be required for that purpose.

Graphical Abstract