Doxycycline in Broiler Chickens:
Dosage and Residue Concerns
Doxycycline is a well-known antibiotic, and its use in broiler chickens has been a topic of research and discussion. In this post, we’ll explore the dosage considerations and residue concerns associated with Doxycycline in broiler chickens.
Recommended Use and Withdrawal Time:
The recommended use of Doxycycline for broiler chickens is at a dosage of 100 mg/L via drinking water with a 7-day withdrawal time (WDT). This dosage and withdrawal period have been established to ensure the safety of chicken meat intended for consumption.
Higher Dosage Study:
However, there’s been interest in studying higher dosages of Doxycycline due to concerns about antimicrobial resistance and a broader disease spectrum. Researchers have examined the use of a higher dosage of 200 mg/L of Doxycycline in the drinking water for five consecutive days.
Serum Concentration and Tissue Depletion:
The study revealed interesting findings. The steady-state concentration of Doxycycline in serum was reached on the third day of medication, at approximately 8.3 μg/mL. Pharmacokinetic parameters, including the elimination constant, half-life, area under the concentration-time curve, and mean residence time, were determined.
Safety Assessment:
A key concern was assessing tissue residues of Doxycycline and ensuring they do not exceed the maximum residue levels (MRL). The study found that the current 7-day WDT regulation remains valid for certain tissues, including the kidney, liver, breast, and leg muscles. Linear regression analysis of the 99% upper distribution limit supported this.
Future Considerations:
The research indicates that higher dosages of Doxycycline may be safely used in broiler chickens, expanding the options for disease treatment and control. However, further studies are warranted to understand the residues in skin/fat tissue.
Comparative Study:
Serum concentration-time profiles of doxycycline in broiler chickens under doxy-FOLA or doxy-ref medication (Figure 1). Figure 2 displays serum concentrations post-IV administration and after doxy-FOLA/doxy-ref dosing on day 1. Table 1 includes pharmacokinetic data for all groups. Notably, doxy-FOLA showed higher bioavailability (156-227%) compared to doxy-ref (13-23%) on days 1 and 5. Doxy-FOLA exhibited a relative bioavailability value (Fr) of 1200% (day 1) and 987% (day 5) vs. doxy-ref. Variables RT and T½β differed significantly (P < 0.05) between doxy-FOLA and doxy-ref groups
Figure 1.
Figure 2.
Mean ± 1 SD of the pharmacokinetic variables in broiler chickens of a single oral dose of 400 ppm (approximately 48 mg/kg/day) of two in-feed formulations of doxycycline, one intended for long acting (doxy-FOLA) and the other a commercially available reference premix (doxy-ref). A third group received a single injection of doxycycline IV (doxy-IV; 48 mg/kg). AUC0-24/MIC and T>MIC ratios doxy-ref and doxy-FOLA are also included.
Table 1.
In conclusion, Doxycycline’s use in broiler chickens is a subject of ongoing research, aiming to optimize dosage for effective treatment while maintaining the safety of the meat for consumption. This research provides insights into safe dosage levels and bioavailability of different formulations, potentially paving the way for improved disease management in broiler chickens.
