QUANTITATIVE RISK ASSESSMENT OF OXYTETRACYCLINE AND TETRACYCLINE RESIDUES IN SLAUGHTERED CATTLE FROM THREE ABATTOIRS IN NIGERIA

ABSTRACT

Tetracylines are among the most commonly available range of broad spectrum antibiotics that are abused and misused in livestock production. Although there are available records on veterinary drug residues; however because of the accessibility of oxytetracycline and tetracycline antibiotics and consequent abuses, there is need for further information on dietary exposure and assessment of risk inherent in ingestion of their residues in treated cattle. Therefore, the concentrations and probability of occurrence of tetracyclines residues in slaughtered cattle meat were assessed.

Four hundred and fifty (450) cattle tissues samples comprising of muscle (50), liver (50) and kidney (50) were randomly collected from three selected major abattoirs (>200 cattle slaughtered/day): Government Abattoir, Agege, Lagos (GAAL), Government  Motor-Park Abattoir, Enugu (GMAE) and Tudun-Wada Abattoir (TWAK), Kaduna. Concentrations of oxytetracycline and tetracycline (μg/kg) in the tissues were determined using Gas chromatography-Mass spectrophotometry. Dietary exposures (μg/kg-bw) to residues of oxytetracycline and tetracycline were assessed using standard deterministic method. The likelihood of exposure to oxytetracycline and tetracycline residues was simulated using Monte Carlo technique to quantitatively assess risk levels. Data were analyzed using descriptive statistics and multivariate analysis of variance using JMP (2010) software (p=0.05) and thereafter compared with Codex Maximum Residue Limits (MRL).

Tetracyclines residues were detected in 63.22% of tested samples. There was no significant difference in total residue concentration (μg/kg) of oxytetracycline between kidney (79.202) and liver (64.897) but there is a difference, when both are compared with muscle (30.033). Considering tetracycline there were no significant differences in all the three tissues: kidney (39.517), liver (17.024) and muscle (6.872). The oxytetracycline (μg/kg) concentration was significantly higher in GAAL (80.217) than TWAK (56.688) and GMAE (37.228). While contrary was the case in tetracycline concentration, where no significant differences were observed in GAAL (40.718) > TWAK (13.069) and GMAE (9.626). This indicates that both in tissues and from locations, residues of oxytetracyline are consistently higher than residues of tetracycline. Also, the oxytetracycline concentration (μg/kg) in cattle tissues was highest in liver (109.094) than in both kidney (91.594) and muscle (39.963) in GAAL. However, in TWAK and GMAE it was in the order of kidney (96.901) > liver (39.389) > muscle (33.774) and kidney (91.594) > liver (46.209) > muscle (16.364), respectively. While there were no significant differences between all locations’ kidney samples and muscle samples for oxytetracycline residues except for liver samples; it was converse for tetracycline concentrations (μg/kg) in cattle tissues from all the locations because there were no significant differences in the residues concentration for all the tissues. The observed residues for both oxytetracycline (59.72ug/kg) and tetracycline (28.23ug/kg) were below the Codex MRLs. Dietary exposures (μg/kg-bw) to oxytetracycline and tetracycline in slaughtered cattle were 0.0284ug/kg bw and 0.0134ug/kg bw respectively. The probability of 1 undetected tetracycline residue-containing beef is 0.0232

Residue concentrations of oxytetracycline and tetracycline in slaughtered cattle from abattoirs in Nigeria were within acceptable safe limits and portend low exposure risk to public health