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African Journal of Pig Farming ISSN 2375-0731 Vol. 7 (7), pp. 001-003, July, 2019. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 

Full Length Research Paper 

 

Antimicrobial residues screening in pigs and 
goats slaughtered in Nsukka Municipal abattoir, 

Southeast Nigeria 

 
Ekene V. Ezenduka* and Chinyere Ugwumba 

 
Department of Public Health and Preventive Medicine, Faculty of Veterinary Medicine, University of Nigeria, 

Nsukka, Enugu State, Nigeria. 
 

Accepted 03 May, 2019 
 

Antimicrobial residue in animal food products is an important index of food safety. Drug residues could result 
from chemotherapeutic or chemoprophylactic use of drugs in food animals. This occurrence of residue in animal 
food products has received enormous worldwide attention from some local, international and public health 
agencies. Samples of tissues/organs from pigs and goats slaughtered at the Nsukka Municipal abattoir, Southeast, 
Nigeria were screened for the presence of antimicrobial residues. Samples collected from the muscles, liver and 
kidney of 40 slaughtered pigs and 40 slaughtered goats were analysed for antimicrobial residues using the four 
plate agar diffusion method. 12 (30%) of the 40 sampled pigs and 10 (25%) of the 40 sampled goats were positive 
for antimicrobial residues. In pigs, antimicrobial residues occur more in the kidney, muscle and liver in that order, 
while in goats they occurred more and equally in kidney and liver than in the muscle. The result of the study 
clearly suggest that the rampant use of antimicrobial drugs in slaughter animals at the Nsukka municipal abattoir 
coupled with non-adherence to withdrawal periods is grossly practiced in Nigeria. This study further confirms the 
need to regulate the use of veterinary drugs in livestock production and to enforce laws guarding against drug 
residues in food animals. 

 

Key words: Residues, antimicrobial, pigs, goats. 
 
INTRODUCTION 

 
Meat is an essential part of mans’ diet and a significant 
percentage of meat and meat products consumed 
worldwide and in Southeast Nigeria in particular comes 
from pigs and goats. The food animals include goats for 
chevon and milk production, and pigs for pork production. 
Challenges of global population growth have led to 
increased efforts at finding resources to enhance animal 
food production to its maximum (Nonga et al., 2009). 
Developments in animal husbandry in the past 50 years 
have resulted in the proliferation of intensive production 
units, especially for pigs and poultry where the animals 
are kept in limited spaces. Such intensive units are prone 
to outbreak of diseases especially in underdeveloped 
countries where the practice of strict biosecurity  
 
 

 
*Corresponding author. E-mail: ev.ezenduka@yahoo.com. Tel:  
+2347061032840. 

 
 
 

 
measures is limited. Routine prophylaxis with low level 
antibiotics was therefore found necessary to prevent 
disease outbreak. The use of antimicrobials in animals for 
therapeutic and prophylactic purposes closely follows 
their uses in humans (Gustafason and Bowen, 1997). 
These drugs are generally used today not only for 
treatment and prevention but to enhance growth and food 
efficiency (Tollefson and Miller, 2000). Approximately 
80% of all food producing animals currently receives 
medication in part or most of their lifetime (Lee et al., 
2001; Pavlov et al., 2008). Antimicrobial use in food 
animals may result to residues in their products (meat, 
milk and egg) especially when the stipulated withdrawal 
period of the agent is not observed. This use of 
antimicrobial drugs in food animals has recently become 
a very important public health issue (Jafari et al., 2007). 
Reports have shown that exposure to these antimicrobial 
residues in food animal products could result to transfer 
of resistant strains of microorganisms to humans, 



 
 
 

 

distortion of the intestinal microflora and bone marrow 
depression among other pathologies in humans (Nisha, 
2008; Jafari et al., 2007). In Southeast Nigeria, pig, goat 
and chicken production is the major food producing 
livestock farming practiced. However, there is a dearth of 
data on the presence of antimicrobial residues in the 
meat of these food animals, hence the need for this 
study. 

 

MATERIALS AND METHODS 
 
Sample collection 
 
Samples were collected from goats and pigs slaughtered at Nsukka 
Municipal abattoir, Enugu State, Southeast, Nigeria. Nsukka is one 
of the three agricultural zones in Enugu State. 10 g each of meat 
(muscle), liver and kidney were collected from 40 goats and 40 
pigs, totalling 120 samples from each species. The samples were 
packaged in polyethylene bags and labelled according to the animal 
from which they were collected. They were then taken to the 
laboratory and processed as described by Oboegbulem and Fidelis 
(1996), by cutting off approximately 2 g of 1 to 2 cm chunk of the 10 
g collected from the abattoir. The samples were processed the 
same day as fresh samples. 

 

Assay for antimicrobial residue 
 
The antimicrobial residue screening was done with the four plate 
agar diffusion test (FPT) using Bacillus subtilis and Staphylococcus 
aureus. The presence of antimicrobial agents in each of the 
samples was confirmed by a complete inhibition of microbial growth 
in an annular zone not less than 2 mm (0.2 cm) around the piece of 
meat. Less than 2 mm of inhibitory zone indicate negative result. 

 

Sensitivity test 
 
An initial sensitivity test to cephaloxin, norfloxacin, gentamycin, 
erythromycin, ciprofloxacin, amoxicillin, streptomycin oxytetracycline 
and clindamycin was done for the stock colonies of B. subtilis and 
S. aureus. 

 

Preliminary test 
 
To assess the efficiency of the four plate test in detecting 
antimicrobial residue in tissue samples, a positive control as 
described by Oboegbulem and Fidelis (1996) was set up by 
injecting oxytetracycline intramuscularly into two chickens daily for 
three consecutive days. They were then sacrificed on the 4th day 
and samples from the breast/thigh muscles, liver and kidney were 
removed and tested by the FPT. 
 

 

RESULTS 

 

Sensitivity test 
 
The stock B. substilis sample was found to be sensitive to 
cephaloxin, norfloxacin, gentamycin, erythromycin, 
ciprofloxacin, tetracycline, clindamycin, trimethoprin and 
streptomycin but less sensitive to amoxil and ampiclox. S. 
aureus stock sample was found to be sensitive to all the 

  
  

 
 

 

aforementioned antimicrobial agents except trimethoprin. 
 

 

Preliminary test 

 

The preliminary test with oxytetracycline showed that all 
tissue samples were positive for tetracycline residue as 
each of the four plates showed a clear zone of inhibition 
for the growth of B. substilis and S. aureus. No such 
inhibition occurred in the negative control plate showing 
the efficiency and sensitivity of the FPT. 
 

 

Antimicrobial residues in test samples from 
slaughtered pigs and goats 

 

The results of the antimicrobial residues in tissue samples 
from slaughtered pigs and goats showed that 12 (30%) of 
the 40 pig samples and 10 (25%) of 40 goat samples 
were positive for antimicrobial residue. 
 

 

Antimicrobial residues in pig organs 

 

Out of a total of 120 organs from slaughtered pigs 
comprising 40 samples from each of the three organs 
(muscle, liver and kidney), eight (20%) muscle samples, 
four (10%) liver samples and 10 (25%) kidney samples 
were positive for antimicrobial residues. 
 

 

Antimicrobial residues in goat organs 

 

Out of a total of 120 organs from slaughtered pigs 
comprising 40 samples from each of the three organs 
(muscle, liver and kidney), 10 (25%) muscle, 12 (30%) 
liver and 12 (30%) kidney samples were positive for 
antimicrobial residues. 
 

 

DISCUSSION 
 
Pig and goat farming are the major food producing 
livestock farming in Southeast Nigeria. Pigs in Nsukka 
area are mostly reared intensively and most of the 
farmers do not employ the services of a veterinarian to 
take care of the animals. They (farmers) tend to treat the 
animals themselves due to uncontrolled availability of 
veterinary drugs with no restriction in purchase (purchase 
without prescription). Goats slaughtered in Nsukka 
abattoir on the other hand come from two sources, the 
Northern part of Nigeria and locally reared West African 
Dwarf (WAD) breed in Nsukka metropolis. The 
occurrence of antimicrobial residue in goat tissues could 
be attributed to the practice of the indigenes selling off 
their mature sick goats after treating to mask clinical 
signs or selling off those that defied treatment. Goat 
owners in the rural areas also tend to sell off their sick 



 
 
 

 

goats due to unavailable resources to employ the 
services of a veterinarian. Most times these goats are 
treated in the lairage awaiting slaughter. The indis-
criminate use of antimicrobial substances and non 
observance of withdrawal period which has been reported 
as the major cause of violative residues in animal food 
products (Pikkemat et al., 2008; Riviere and Sundlof, 
2001) have led to the availability of unsafe pork and 
chevon to consumers. Few other works done in different 
parts of the country also detected antimicrobial residues 
in different animal species (Ibrahim et al., 2010; 
Ezenduka et al., 2011; Dipeolu and Alonge, 2002; Kabir 
et al., 2002) and they also attributed the major cause of 
drug residue in food of animal origin to non-adherence to 
withdrawal periods and misuse and abuse of veterinary 
drugs. The lack of the enforcement of regulatory laws to 
veterinary drug use in Nigeria has led to the abuse and 
misuse of drugs in food animals. The result of this work 
and other works that detected residue in food animals in 
Nigeria will create awareness to the stake holders 
(government and consumers) gearing to necessitate the 
enforcement of adherence to withdrawal periods, 
effective monitoring and surveillance of drug residues in 
meat animals and control of drug use in food animals to 
prevent the occurrence of violative drug residue.  

The European FPT is essentially a multiresidue tech-
nique for screening animal products; it does not however 
identify the incriminating antimicrobial or the quantity of 
residue. Despite its limitations, the use of bacteria in 
detecting residues has since been useful in the meat 
industry (Okerman et al., 1998). 
 

 
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