Residue depletion study and withdrawal period in milk for intramuscular gentamicin in dairy cows using LC-MS/MS
- Author:
DoHui KIM
1
;
Su Min NAM
;
Hyoungjoon MOON
;
Mi-Young PARK
;
Hyun-Ok KU
;
Hee YI
;
Hwan Goo KANG
Author Information
- Publication Type:Research Report
- From:Journal of Veterinary Science 2025;26(6):e89-
- CountryRepublic of Korea
- Language:English
-
Abstract:
Objective:This study aimed to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify gentamicin residues in milk and to establish a withdrawal period for an intramuscular gentamicin product in dairy cows.
Methods:Nine Holstein cows received a gentamicin product (50 mg gentamicin sulfate/ mL) at 0.1 mL/kg twice daily at 12 h intervals via intramuscular injection. Milk samples were collected before dosing and at 12 h intervals up to 168 h after the final administration and analysed with a validated LC-MS/MS method using heptafluorobutyric acid as an ion-pairing reagent.
Results:The method showed recovery rates of 86%–104%, coefficients of variation of 3%–11%, and limits of detection and quantitation of 23 and 70 ng/mL, respectively. Mean gentamicin concentrations exceeded the maximum residue limit (MRL; 0.2 mg/kg) at 12 h during treatment and 12 h after the final administration, and were < MRL in all cows from 36 h after the last dose. Based on residue depletion data and a national non-statistical guideline, a withdrawal period of 40–48 h was derived, and the regulatory withdrawal period for this product was established as 3 days.
Conclusions:and Relevance: The validated LC-MS/MS method enables rapid quantitation of gentamicin residues in bovine milk. A 3-day regulatory withdrawal period for this product supports milk safety, regulatory compliance, and practical use in dairy herds.
